Buderus 500 - 28/C, 500 - 24/C, 500 - 24/S Servicing Manual

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Page 1

7214 8900 – 02/2006 GB(EN) For the installer

Servicing manual

Gas wall hung Boiler condensing Buderus 500 - 24/S Buderus 500 - 24/C Buderus 500 - 28/C

Please read thoroughly before attempting fault diagnosis

Page 2

F The boiler meets the basic requirements of the

appropriate standards and directives. Conformity has been substantiated by the proper documents which - together with the declaration of conformity - are filed with the manufacturer.

Subject to technical modifications!

Constant development efforts may result in minor deviations in illustrations, functional steps and technical data.

Updating the documentation

If you have suggestions for improvement or have found discrepancies, please do not hesitate to contact us.

We reserve the right to make technical modifications Buderus Ltd. • http://www.buderus-domestic.co.uk

2 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

Page 3

box 1 List of contents

1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2 Servicing manual user guide . . . . . . . . . . . 10

3 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

4 Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

5 Symptoms . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

6 Diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

7 Actions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

8 Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

box 2 Preface

These service instructions apply to: Buderus wall-mounted condensing gas boilers 500 - 24/S, 500 - 24/C and 500 - 28/C.

Model: C Type: GB/IE II

13(x)

, C

33(x)

20 mbar, 37 mbar

2H3P

53(x)

, C

73(x)

Power rating: 230 VAC, 50 Hz, IP X4D Fuse rating: 1.25 Ampere slow blow The boiler unit consists of the following components: – 500 Gas condensing boiler

– 28 Maximum output is 28 kW – C Combination boiler (with integrated hot water

supply)

– S System boiler.

9 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

Important general instructions for use

Only use the boiler in accordance with its designated use and the service instructions. Installation, maintenance and repair must be carried out by competent service engineers (e.g. CORGI registered). Only use the boiler in conjunction with the accessories and spare parts indicated in the installation, maintenance and service instructions. Other accessories and consumables may only be used if they are expressly provided for the designated use and if system performance and safety are not affected in any way.

The boiler is suitable for connection to fully pumped, sealed water systems ONLY. Adequate arrangements for completely draining the system by provision of draining valves must be provided in the installation pipework.

Pipework from the boiler is routed downwards as standard, but may be routed upwards behind the boiler using the wall spacing frame.

Subject to technical modifications.

As a result of our policy of constant development, there may be small differences between illustrations, functional steps and technical data.

G. C. Aplliance No. :

Buderus 500-24/S 41-110-24 Buderus 500-24/C 41-110-04 Buderus 500-28/C 41-110-03

BENCHMARK' Log Book

All Buderus gas fired boilers now include an installation,

Other manuals available for this boiler are: – user manual;

– installation and maintenance instructions; – wall spacing frame instructions.

commissioning and service record log book. The details of the log book will be required in the event of any warranty work being requested. Please complete the appropriate sections on completion of the installation and commissioning.

REMEMBER: Please hand the log book back to the user.

We reserve the right to make technical modifications Buderus Ltd. • http://www.buderus-domestic.co.uk

Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 3

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General1

1 General

box 3 Regulations and directives

It is a requirement that all gas appliances are installed and serviced by a CORGI registered installer in accordance with the regulations. Failure to service appliances correctly could lead to prosecution. It is in your own interest, and that of safety, to ensure the law is complied with.

It is a requirement and in your own interest, and that of safety that this boiler must be serviced by a CORGI registered installer, in accordance with the relevant requirements of the current Gas Safety (Installation and Use) Regulations, The Building Regulations, current I.E.E. Wiring Regulations and the relevant British Standard Codes of Practise.

Detailed recommendations are contained in the following British Standard Codes of Practice:

BS. 5440:1 Flues (for gas appliances of rated input not

exceeding 70 kW).

BS. 5440:2 Ventilation (for gas appliances of rated

input not exceeding 70 kW).

BS. 5449 Forced circulation hot water systems. BS. 5546 Installation of gas hot water supplies for

domestic purposes (2nd. family Gases).

BS. 6798 Installation of gas fired hot water boilers of

rated input not exceeding 60 kW.

BS. 6891 Low pressure installation pipes. BS. 7593: 1992: Code of practice for treatment of water in

domestic hot water central heating systems.

IGE/UP/1b Tightness testing and purging domestic

sized gas installations.

Health and & Safety Document No. 635.

The Electricity at Work Regulations, 1989.

The manufacturer's notes must not be taken, in any way, as overriding statutory obligations.

The design and construction of the Buderus wall-mounted condensing gas boiler conforms to the basic specifications listed in the European directive governing gas-fired appliances 90/396/EEC, and with respect to EN 625, EN 483 and EN 677.

INOTE:

Observe the corresponding technical rules and the building supervisory and statutory regulations when installing and operating the system.

HWARNING!

Keep the burner-control unit housing CLOSED when working on water-bearing components.

INOTE:

It is mandatory to clean and service the system once a year. This includes an inspection of the entire system to see if it is in full working order. Defects and faults must be eliminated immediately.

INOTE:

When instructions aren’t followed, warranty expires.

INOTE:

Condensing boilers work more efficient if the CH flow/return temperature is as low as possible.

Timber Framed Buildings

If the boiler is to be fitted in a timber framed building it should be fitted in accordance with the Institute of Gas Engineering document IGE/UP/7:1998 and BS 5440:1.

Bathroom Installations

This appliance is rated IP X4D. The boiler may be installed in any room or internal space,

although particular attention is drawn to the requirements of the current IEE (BS.7671) Wiring Regulations and, in Scot land, the electrical provisions of the building regulations applicable in Scotland, with respect to the installation of the boiler in a room or internal space containing a bath or shower.

If the appliance is to be installed or serviced in a room containing a bath or shower then, providing water jets are not going to be used for cleaning purposes (as in communal baths/showers), the appliance can be installed or serviced in Zone 3, as detailed in BS.7671.

Compartment Installations

A compartment used to enclose the boiler should be designed and constructed especially for this purpose. An existing cupboard or compartment may be used, provided that it is modified for the purpose.

In both cases, details of essential features of cupboard/ compartment design, including airing cupboard installation, are to conform to the following: BS 6798 (No cupboard ventilation is required - see 'Air Supply' for details).

It is not necessary to have a purpose-provided air vent in the room or internal space in which the boiler is installed. Neither is it necessary to ventilate a cupboard or compartment in which the boiler is installed, due to the low surface tempera tures of the boiler casing during operation; therefore the requirements of BS 6798, Clause 12, and BS 5440:2 may be disregarded.

The permanent clearances required are: in front: 8 mm below: 21 mm right side: 8 mm left side: 8 mm above: 21 mm

The position selected for installation MUST allow adequate space for servicing in front of the boiler. See table below:

in front: 350 mm below: 180 mm right side: 8 mm left side: 8 mm above: 200 mm

In addition, sufficient space may be required to allow lifting access to the wall mounting bracket. Wall-mounted condensing gas combi boilers must only be operated with Buderus purpose made gas systems, which are certified for this type of boiler.

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4 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

Page 5

Observe the relevant standards, regulations and legislation of the country or region of final use.

ACAUTION!

Use this boiler for its intended purpose only.

ADANGER!

Notes relating to the heating system water.

Thoroughly flush the system before it is filled with water. Use only untreated water or water treatment product such as Sentinel X100 to fill and top up the system. For more information about Sentinel call 0151 420

9563. When using water treatment, only products suitable for

use with Buderus heat exchangers are permitted (e.g. Sentinel X100). Your warranty is at risk if an incorrect water treatment product is used in conjunction with this appliance. For more information, contact Buderus Technical Product Support Department. It is most important that the correct concentration of the water treatment product is maintained in accordance with the manufacturer's instructions. If the boiler is used in an existing system any unsuitable additives MUST be removed by thorough cleaning. BS.7593:1992 details the steps necessary to clean a domestic central heating system. In hard water areas, treatment to prevent lime scale may be necessary - however, the use of artificially softened water is NOT permitted. Under no circumstances should the boiler be fired before the system has been thoroughly flushed. Do not use artificially softened water. Only plastic pipework containing a polymeric barrier should be used. It is allowed to use copper for the first 600 mm.

INOTE:

Notes relating to domestic hot water

z The domestic hot water service must be in

accordance with BS 5546 and BS 6700.

z The boilers are suitable for connection to most types

of washing machine and dishwasher appliances.

z When connecting to suitable showers, ensure that:

a. The shower is capable of accepting mains

pressures and temperatures up to 65 °C.

b. The shower is ideally thermostatic or pressure

balancing.

z Where temporary hardness exceeds 150 mg/litre,

it is recommended that a proprietary scale reducing device is fitted into the boiler cold supply with the requirements of the local water company.

ACAUTION!

Provision must be made to accommodate the expansion of DHW contained within the appliance, where a back flow prevention device is fitted

67989: §5.4.3.

BS.

General 1

box 4 Hazard definitions and abbreviations

Hazard definitions

ADANGER:

Indicates the presence of hazards that will cause severe personal injury, death or substantial property damage.

AWARNING:

Indicates the presence of hazards that can cause severe personal injury, death or substantial property damage.

ACAUTION:

Indicates presence of hazards that will or cause minor personal injury or property damage.

INOTICE:

Indicates special instructions on installation, operation or maintenance that are important but not related to personal injury or property damage.

Abbreviations

AV = Air Vent BCT = Buderus cylinder thermostat BDV = Buderus diverter valve CB = Connection Block CH = Central Heating CHF = Central Heating Flow CHR = Central Heating Return CT = Cylinder Thermostat CWDO = Condensate water drainage outlet DHW = Domestic Hot Water DV = Diverter Valve E=Earth L=Live LSV = Lock Shield Valve MCW = Mains Cold Water N = Neutal JB = Junction Box / RTH Relay PL = Permanent Live Prog = Programmer PRV = Pressure relief valve (safety valve) RT = Room Thermostat RV = ModuLink 250 RF Receiver T=Timer TRV = Thermostatic Radiator Valve WC = Wiring Centre ZV = Two Port Zone Valve

Safe handling of substances

No asbestos, mercury or CFCs are included in any part of the boiler and its manufacture.

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Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 5

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General1

box 5 Technical specifications

Buderus

Hot water capacity (combination boilers)

Rated thermal load for CH

Rated thermal load for preparing DHW

Rated heating capacity for system temperature (modulating from 30° to 100°) Heating curve 75/60 °C

Heating curve 40/30 °C

Seasonal efficiency (SEDBUK) for natural gas

for propane

Maximum gas consumption, hot water/tank

Maximum gas consumption, heating

Boiler efficiency (40/30°C) (lower value/upper value) (full load)

Boiler efficiency (40/30°C) (lower value) (partial load)

Boiler efficiency (40/30°C) (upper value) (partial load)

Boiler efficiency (75/60 °C) (lower value/upper value) (full load)

Boiler efficiency (75/60°C) (lower value/upper value) (partial load)

Chimney loss with burner shut down (standby heat loss) at nominal thermal load

Hot water circuit

ΔT at residual head of 200 mbar

Maximum flow temperature

Permitted system pressure

Expansion vessel

Capacity of expansion vessel

Admission pressure of expansion vessel

Plate heat exchanger

DHW flow rate at 35 °C rise

Supply pressure of hot water

Adjustable DHW temperature

Pipe connections

Condensate outlet

CH flow/return (compression fitting)

MCW inlet / DHW outlet (compression fitting)

Gas on installation frame (compression fitting)

Pressure relief valve

Flue-gas connection

Type of flue-gas connection (model)

Ø Flue gas pipe / combustion-air inlet

Unit 500-24/S 500-24/C 500-28/C

kW 5.7 – 28.5

kW 5.7 – 23.0 5.7 – 23.0 5.7 – 23.0

kW 5.7 – 28.5 5.7 – 23.0 5.7 – 28.5

kW kW

% %

m3/h 3.02 2.43 3.02

m3/h 2.43 2.43 2.43

% 104 / 104 104 / 104 104 / 104

% 107 107 107

% 96.3 96.3 96.3

% 95.7 / 86.2 95.7 / 86.2 95.7 / 86.2

% 94.6 / 85.2 94.6 / 85.2 94.6 / 85.2

% 1.2 1.2 1.2

°C <20 <20 <20

°C 80 80 80

bar 1.0 – 3.0 1.0 – 3.0 1.0 – 3.0

l 7.5 7.5 7.5

bar 1.0 1.0 1.0

l/min – 9.4 11.7

bar – 0.8 - 10.0 0.9 - 10.0

°C – 40 - 60 40 - 60

Ø mm 21.5 21.5 21.5

Ø mm 22.0 22.0 22.0

Ø mm 15.0 15.0 15.0

Ø mm 22.0 22.0 22.0

Ø mm 15 mm (adapter supplied with boiler)

mm 60/100 (accessory)

(with external

tank)

5.3 – 22.0

6.0 – 24.0

90.3

92.3

6.0 – 24.0 5.7 – 28.5

5.3 – 22.0

6.0 – 24.0

90.3

92.3

, C

33(x)

, C

53(x)

13(x)

, C

5.3 – 22.0

6.0 – 24.0

90.3

92.3

73(x)

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6 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

Page 7

box 5 Technical specifications

Buderus

Flue-gas readings

Condensate water quantity, natural gas, 40/30 °C

Exhaust-fume mass-flow rate Full load Part-load

Exhaust-fume temperature, full load Heating curve 75/60 °C Heating curve 40/30 °C

Exhaust-fume temperature, partial load Heating curve 75/60 °C Heating curve 40/30 °C

CO2 full load, natural gas standard test gas G20

CO2 full load, natural gas standard test gas G31 propane

Standard emission factor NO

Standard emission factor CO

Flow pressure available for use

Electrical specifications

Mains connection voltage

Electrical protection rating

Electrical power consumption, standby

Electrical power consumption, partial load

Electrical power consumption, full load

Dimensions and weight of boiler

height × width × depth

Weight without casing Weight with casing

Gas

Category of gas as per EN 437 for GB

Gas injector Ø natural gas H (G20)

Gas injector Ø propane P (G31)

Venturi article number

Natural gas H

Propane P

Other items

Pump

Pump over-run time: Heating system default adjustments External cylinder Plate heat exchanger (ECO) Plate heat exchanger (warm start) After service mode

General 1

Unit 500-24/S 500-24/C 500-28/C

l/h 1.6

g/s g/s

°C °C

% 9,2

% 10.3

ppm (mg/kWh) <30

ppm (mg/kWh) <22

Pa 75

Vac 230 (50 Hz)

W 4

W 88

W 110

mm 780 × 460 × 330 780 × 460 × 330 780 × 460 × 330

kg kg

mm 4.45 4.45 4.45

mm 3.45 3.45 3.45

30 33

20 mbar, 37 mbar (natural gas H and propane P)

2H3P

423.072A 423.072A 423.072A

Delivered ready for operation, adjusted to Wobbe index

14.1 kWh/m

Deemed suitable for use with propane after inspection

5 minutes

30 - 40 seconds

1 minute

(with reference to 15 °C, 1013 mbar),

applicable to Wobbe index range

Markings on gas classification plate:

Configured category: G

by a registered Corgi heating engineer.

Markings on gas classification plate:

Configured category: 3P

– –

10.6

4.3

77 55

60 35

IP X4D

31 34

11.3 to 15.2 kWh/m

20 - 2E - 20 mbar

G 31_30-50 mbar.

UP 15-50

5 minutes

–

30 - 40 seconds

30 seconds

1 minute

30 - 40 seconds

30 seconds

31 34

5 minutes

–

1 minute

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Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 7

Page 8

General1

box 6 Overview Buderus 500

15 16 17

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8 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

Page 9

General 1

box 7 Key to terms

Item 1: Ionisation electrode Item 2: Glow ignitor Item 3: Automatic air vent Item 4: Safety sensor Item 5: Clamp for heat exchanger cover Item 6: Plate heat exchanger Item 7: Condensate trap Item 8: Flow NTC sensor Item 9: DHW flow regulator Item 10: Pressure gauge Item 11: Concentric flue gas adaptor Item 12 Fan Item 13: Frame Item 14: Gas/Air unit Item 15: Sight glass Item 16: Gas valve Item 17: Heat exchanger Item 18: Gas supply pipe Item 19: Identification plate of boiler Item 20: Air silencer tube Item 21: Flue gas pipe Item 22: Flue gas safety temperature limiter (STL) Item 23: Pump 15-50 Item 24: Pressure relief valve discharge pipe Item 25: Syphon Item 26: Identification plate showing gas category Item 27: Connection block Item 28: DBA control panel Item 29: RTH converter / junction box

box 8 General points

AWARNING!

DANGER OF FATAL ACCIDENT FROM EXPLOSIVE FUMES

If you smell gas

z There is a danger of explosion. z No naked lights. No smoking. DO NOT use a naked

light to detect possible leaks.

z DO NOT operate any device that is likely to produce

sparks.

z DO NOT operate electrical switches of any kind

(including telephones, plug-in devices and doorbells)

z Shut off the gas supply at the main valve. z Open doors and windows. z Warn other occupants of the building (but DO NOT

use the house intercom or doorbells).

z Contact the gas supplier from a telephone located

outside the building.

z If you detect an audible gas leak, evacuate the

building immediately, prevent other persons from entering, and notify the police and fire service immediately (from a telephone OUTSIDE the building).

HWARNING!

DANGER OF FATAL ACCIDENT

due to electric shock

ACAUTION!

General information on maintenance work.

IUSER INSTRUCTIONS

Instructions for optimum usage, correct adjustment of the boiler and other useful information.

ACAUTION!

Use eye protection, inhalation protection, hearing, gloves, shoes etc. on the right time.

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Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 9

Page 10

Servicing manual user guide2

2 Servicing manual user guide

box 9

This document consists of various sections. These in turn contain subsections/boxes in the form of text or tables.

Subsections/boxes inside text and tables are identified by a small grey box. Each subsection/box is assigned its own identification number.

These subsections/boxes are divided into operating steps. If an operating step involves the taking of a yes/no decision, the right-hand side of the table indicates which subsection / operating step you should proceed (cross reference).

Section

Cross reference to subsection or operating step

Subsection/box

Diagnosis6

box 24

step 28 Check the actuation of the servomotor of the internal three-way valve, see box 186.

step 29 Does the servomotor of the internal three-way valve start up correctly? Yes:

step 30 Replace the servomotor of the internal three-way valve, see box 191.

step 31 Check the power supply cable of the internal three-way valve, see box 192.

step 32 Is the power supply cable of the internal three-way valve in good condition? Yes:

step 33 Replace the cable loom (or the affected part thereof).

step 34 Check the movement of the servomotor of the

see box 212.

step 35 Does the servomotor of the

step 36 Check to ensure that the the

see box 228.

step 37 Has the

step 38 Install the Buderus 24V AC external three-way valve correctly, see box 228. o box 43

step 39 Check to ensure that the

step 40 Does the Buderus 24V AC external three-way valve actuate correctly? Yes:

step 41 Replace the servomotor of the

step 42 Check the wiring of the Buderus 24V AC external three-way valve, see box 221.

step 43 Is the wiring of the

step 44 Replace the wiring of the Buderus 24V AC external three-way valve.

step 45 Check the drive mechanism of the

step 46 Is the drive mechanism of the Buderus 24V AC external three-way valve working correctly? Yes:

step 47 Replace the internal components of the

step 48 Check the wiring of the

On combi boiler supply: hot water available, but no heating operation.

On system boiler supply: no heating operation.

Hot water may be available, but no heating operation.

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24 Servicing manual Gas condensing bo iler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2005

Buderus 24V AC external three-way valve been fitted correctly? Yes:

see box 213 and box 229.

moving plug-and-socket connection and the control panel as per box 288.

box 25

step 1 Check to ensure that the power supply cable to the RTH converter/Junction box has been installed correctly,

see box 286.

step 2 Is the 230V connection to the RTH converter/Junction box fitted correctly? Yes:

step 3 Correctly attach the switch live to terminal 1 and Neutral to terminal 2 on the 230V connector, see box 286.

step 4 Disconnect black leads from terminals 1 & 2 on the back of the DBA and test for continuity between the two

leads.  No continuity check S/L and N connections are made correctly and that there is 230v between the two. Replace RTH converter/Junction box. Continuity reconnect the cables to terminals 1 & 2 and check the connections between the terminals and the DBA.

Buderus 24V AC external three-way valve is actuated correctly,

Buderus 24V AC external three-way valve in correct condition?

Buderus 24V AC external three-way valve between the connection box or

Buderus 24V AC external three-way valve, 

Buderus 24V AC external three-way valve operate correctly? Yes:

Buderus 24V AC external three-way valve has been fitted correctly,

Buderus 24V AC external three-way valve, see box 218.

Buderus 24V AC external three-way valve, see box 222.

Buderus 24V AC external three-way valve, see box 225.

o step 30

o step 31

No:

o box 43

o box 42

No: o step 33

o box 43

o step 36

o step 39

No:

o step 45

o step 38

No:

o step 41

o step 42

No:

o box 43

o step 47

Yes:

o step 44

No:

o box 43

o box 42

o step 47

No:

o box 43

o step 4

o step 3

No:

o box 43



Operating step number

Explanation of this subject starts in this box. The following boxes can be relevant as well.

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10 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

Page 11

3 Operation

box 10 Operation

box 11

Operation

General points

The central boiler can be run from the DBA control panel (item 1).

3 4 5 6

item 1: Mains switch 0/1 item 2: Reset button item 3: Service button item 4: Display item 5: Menu button item 6: Adjusting arrow UP item 7: Adjusting arrow DOWN

You can navigate through the menu structure of the central boiler using the service button, reset button,

C-button and

D-button (item 2, 3, 5, 6 and 7) and the display (item 4),

box 12 to 14.

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Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 11

Page 12

Operation3

box 12 Normal Operation menu

step 1

step 2

step 3

step 4 Continue with Normal Operation menu ?

step 5

step 6 Keep the

[24] Current CH flow temperature, in °C. See also box 20.

Keep the

D-button pressed.

[00] current DHW flow rate, in litres per minute

Release the

D-button. → step 1

C-button pressed.

Yes:

No:

→ step 6

→ step 5

step 7

[0h] Operating code. See also box 20

In this case: The boiler is ready for operation. No current heat requirement.

box 13 Service Mode menu (no hot water is available during service-mode operation)

step 1 [24] Current CH flow temperature, in °C. See also box 20.

step 2 Activate service mode?

step 3

step 4

step 5 Briefly press the

step 6

step 7 Exit partial-load service mode?

step 8

step 9 Briefly press the

step 10

Press the

A-button once.

,24] As soon as the spanner symbol on the left-hand side of the display and the flame appear, the boiler will

run for 30 minutes in service mode. The maximum CH flow temperature (as configured in the “Settings” menu) applies in this case.

C-button.

Partial-load service mode Adjust the gas/air ratio as required. See box 233 and box 143.

Press the

A-button once.

[lo] is activated. Check the gas/air ratio and ionisation current.

C-button.

Full-load service mode accordingly box 230.

,hi] is activated. Check the working gas input pressure, or analyse the exhaust gas

Yes:

No:

Yes:

No:

→ step 4

→ step 3

→ step 1

→ step 8

→ step 6

step 11 Exit full-load service mode?

step 12

step 13 Service mode is deactivated.

Press the

A-button once, or wait for service mode to expire (after 30 minutes).

Yes:

No:

→ step 12

→ step 10

→ step 1

box 14 Settings menu

step 1 [24] Current CH flow temperature, in °C. See also box 17.

step 2 Open “Settings” menu?

step 3 Press the

step 4 Is boiler a combination boiler with warm start ? Yes:

step 5

step 6 Adjust configured hot water mode ? Yes:

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[pr# ( H / I ) Configured hot water mode. As soon as [pr# is displayed, you can verify the current hot

water mode, or adjust it as required. See also box 18.

E-button once.

Yes:

No:

→ step 3

→ step 1

→ step 4

→ step 5

→ step 9

→ step 7

→ step 8

12 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

Page 13

box 14 Settings menu

step 7

Use single or multiple operation of the

[pr# ( H ): Hot water mode to ECO, [pr`( I ): Hot water mode to warm start.

step 8

step 9

Press the

E-button once.

[60) As soon as the DHW temperature (in °C) appears on the display [60), you can read the current

DHW temperature, or adjust it as required. See also box 18.

D- and C-buttons to activate and disable hot water mode.

Operation

step 10

step 11

step 12

step 13

step 14

step 15

Adjust DHW temperature ? Yes:

Lower: lower the DHW temperature with the Higher: increase the DHW temperature with the

Press the

[pr' ( K / L ) Configured heating mode. As soon as [pr' is displayed, you can verify the current

heating mode, or adjust it as required. See also box 18.

Adjust configured heating mode ?

Use single or multiple operation of the

[pr. (K ): Heating mode on, [pr; (L ): Heating mode off.

step 16 Press the

step 17

step 18

step 19

step 20

step 21 Press the

[80. Configure CH flow temperature, in °C. See also box 18. As soon as [80. is displayed, you can verify

the current CH flow temperature, or adjust it as required.

Adjust CH flow temperature ?

Lower: lower the CH flow temperature with the Higher: increase the CH flow temperature with the

Has at least 10 seconds passed without a button being pressed and/or was mains supply interrupted ?

E-button once.

D-button.

C-button.

D- and C-buttons to activate and disable heating mode.

D-button.

C-button.

No:

Yes:

No:

Yes:

No:

Yes:

No:

→ step 11

→ step 12

→ step 15

→ step 16

→ step 19

→ step 20

→ step 22

→ step 21

step 22 Any adjustments that you have made will now be confirmed.

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→ step 1

Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 13

Page 14

Function4

4 Function

box 15 Boiler Functions

Start phase

step 1 Turn the mains switch to “ON”.

step 2 Turn the operating switch on the DBA control panel of the boiler to position “1“ (ON) – see also box 11.

step 3 Is a 3-way valve fitted? Yes:

step 4 Is the 3-way valve set to “hot water mode”? Yes:

step 5 The Buderus 24V AC external 3-way valve is turned to “heating mode” in 7.5 seconds, while an internal 3-way

step 6

step 7

step 8

step 9 Has the pre purge been completed correctly? Yes:

step 10 Deal with fault. The error code, which is now displayed, can be found in box 20. Deal with the fault.

step 11

step 12 Start of pump over-run time via the heating system.

step 13 Has the pump over-run time expired? Yes:

step 14 Is the boiler set to warm start for hot water and/or is an external storage-type water heater connected? Yes:

step 15 Is the plate heat exchanger triggered and/or is the temperature in the external storage-type water heater at least

step 16 Is there a current heat requirement from the (room) temperature controller? Yes:

step 17 Is the current CH flow temperature lower than 7 °C (frost protection)? Yes:

step 18 The pump stops.

step 19 Has the pump been out of use for more than 24 hours? Yes:

step 20 Is the plate heat exchanger triggered and/or is the temperature in the external storage-type water heater at least

step 21 Is there a current heat requirement from the (room) temperature controller? Yes:

valve is turned to “heating mode” in 2 seconds.

,00{ The display on the DBA control panel of the boiler is checked (maximum of one second). [24] Current CH flow temperature, in °C. See also box 20. C [0u] The boiler begins to warm up. Start of pre purge phase.

The fan runs for 15 seconds at about 60 % of maximum speed.

Checking phase

Operating phase

C [0h] Operating code. See also box 20. The boiler is ready for operation.

No current heat requirement.

The pump over-run time:

– via the heating system, factory-adjusted to 5 minutes; – via the external reservoir, set to 30-40 seconds; – via the plate heat exchanger (ECO), set to 30-40 seconds; – via the plate heat exchanger (warm start), set to 30 seconds; – after service mode, 1 minute.

5 °C below the temperature set at the DBA control panel?

No:

Yes:

No:

Yes:

No:

→ step 4

→ step 6

→ step 5

→ step 6

→ step 11

→ step 10

→ step 18

→ step 14

→ step 15

→ step 16

→ step 28

→ step 16

→ step 46

→ step 19

→ step 62

→ step 18

→ step 23

→ step 20

→ step 28

→ step 21

→ step 46

→ step 22

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14 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

Page 15

Function 4

box 15 Boiler Functions

step 22 Is the current CH flow temperature lower than 7 °C (frost protection)? Yes: → step 62

No:

→ step 23

step 23 The pump is run for 10 seconds in order to prevent it from seizing up.

No:

Yes:

No:

→ step 18

→ step 25

→ step 28

→ step 26

→ step 46

→ step 27

→ step 62

→ step 24

→ step 32

→ step 72

→ step 39

→ step 34

→ step 35

→ step 32

→ step 29

→ step 38

→ step 46

→ step 19

step 24 Have 10 seconds elapsed? Yes:

step 25 Is the plate heat exchanger triggered and/or is the temperature in the external storage-type water heater at least

5 °C below the temperature set at the DBA control panel?

step 26 Is there a current heat requirement from the (room) temperature controller? Yes:

step 27 Is the current CH flow temperature lower than 7 °C (frost protection)? Yes:

step 28 The symbol “

step 29

step 30

step 31 Does the ionisation current exceed 1.4 µA (microamperes) within 5 seconds? Yes:

step 32

step 33 Is the temperature in the plate heat exchanger higher than the temperature entered via the DBA control panel? Yes:

step 34 Is the CH flow temperature 46 °C higher than the preset DHW temperature and/or higher than 93 °C? Yes:

step 35

step 36 The symbol ”

step 37 The fan stops after 30 seconds.

step 38 Is the CH flow temperature lower than the preset DHW temperature plus 35°C? Yes:

step 39 The gas valve is closed and the burner is shut down.

step 40 The symbol

step 41 Start of pump over-run time via the cylinder.

step 42 The fan stops.

step 43

step 44 The 3-way valve turns to the heating mode setting for two seconds.

step 45 Is there a current heat requirement from the (room) temperature controller? Yes:

step 46 The symbol

step 47

step 48

C [0c] The fan runs at 49 % of capacity.

The 3-way valve turns to the hot water setting for two seconds. The glow ignitor is activated for two seconds.

C [0l] Ignition phase: The gas valve is opened. The glow ignitor is activated for one second, followed by

alternating half-second periods of inactivity and activity until five seconds have elapsed.

C [=h] The boiler is in hot water mode. If there has been a power cut: The startup load on the boiler is 49%

for the first 13 seconds for the purposes of flow monitoring. It is then increased or decreased accordingly. The symbol ”

C [0y] The gas valve is closed and the burner is shut down.

Start of pre purge phase (10 seconds).

C [0h] The pump stops.

The symbol “

C [0c] The fan runs at 49 % of capacity. The pump is started up.

The glow ignitor is activated for seven seconds.

C [0l] Ignition phase: The gas valve is opened.

H" or “I" for hot water mode on the DBA control panel display lights up.

G “ lights up.

G “ goes out.

G goes out.

H" or “I" goes out.

K lights up.

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Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 15

Page 16

Function4

box 15 Boiler Functions

step 49 Does the ionisation current exceed 1.4 µA (microamperes)) within 5 seconds? Yes: → step 50

No:

→ step 72

step 50

step 51 Is there a heating requirement from the (room) temperature controller? Yes:

step 52 Is the heat system flow temperature 6 °C higher than the target setting?

step 53

step 54 The symbol

step 55 The fan stops.

step 56 Is the CH flow temperature

step 57 The symbol “

step 58

step 59 The symbol ”

step 60 Start of pump over-run time via the heating system. The pump over-run time via the heating system is 5 minutes.

step 61 The fan stops.

step 62 The symbol “

step 63

step 64

step 65 Does the ionisation current exceed 1.4 µA (microamperes) within 5 seconds? Yes:

step 66

step 67 Is the current CH flow temperature higher than 15 °C? Yes:

step 68 The symbol “

step 69

step 70 Start of pump over-run time via the heating system. The pump over-run time via the heating system is 5 minutes.

step 71 The fan stops.

[-h] The boiler is in heating mode. The symbol G lights up.

The startup load on the boiler is 49% for the first 13 seconds for the purposes of flow monitoring. It is then increased or decreased.

(The target setting is entered at the DBA control panel if room-temperature adjustment is required)

C [0y] The gas valve is closed and the burner is shut down.

G goes out.

≥ 6 °C lower than the target setting? Yes: → step 47

K “ goes out.

C [0h] The gas valve is closed and the burner is shut down.

G “ goes out.

Start of the post purge phase of fan (10 seconds).

K “ lights up.

C [0c] The fan starts up. The pump is started up.

The glow ignitor is activated for seven seconds.

C [0l] Ignition phase: The gas valve is opened.

C [-h] The symbol ” G “ lights up. The boiler is in heating mode.

K goes out.

C [0h] The gas valve is closed. The burner is shut down. The symbol G goes out.

Start of the post purge phase of fan (10 seconds).

No:

Yes:

No:

→ step 52

→ step 57

→ step 53

→ step 50

→ step 53

→ step 13

→ step 66

→ box 36

→ step 68

→ step 67

→ step 13

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16 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

Page 17

5Symptoms

box 16 Display icons

Symptoms 5

Display indication

I J

Key to display indication

Service mode

Ionisation signal (flame monitoring)

Hot water mode “ECO” setting or hot water requirement

Hot water mode “warm start” setting or hot water requirement

Standby, hot water mode to “warm start”

Heating mode or heating requirement

Summer operation, no heating mode, hot water only

box 17 Display readings

Display readings

[24]

Key to display reading

Current CH flow temperature

box 18 Control-panel settings

Button

Display Setting

Key to display setting

Unit

°C

Range

[30]

Unit

–

Range

Factory default setting

[80]

1x A<24]

C[lo]

A C [hi]

E[pr#

E [60)

Service mode

Service mode, partial load % 25

Service mode, full load % 100

End service mode (or wait for 30 minutes)

Hot water mode Only applies to combi boilers

DHW temperature

H = Hot water supply to ECO

I = Hot water mode to warm start

°C

40 – 60

K = Heating mode ON

E[pr'

Heating mode

L = Heating mode OFF

E [80.

[//]

= flashing

When it appears on the display at a system boiler, please connect a link between terminal 3 and 4 on the back side of the

CH flow temperature

DBA control panel (hot water cylinder sensor) or make sure that the hot water cylinder sensor is fitted securely.

box 19 Displaycodes

Normaly you see the current CH flow temperature. By pushing the "C"-button you will see the current operation code.

Blocking:

The boiler stops heating and will wait until the blocking is solved.

Locking:

Displaycode is blinking and also a blinking wrench "F" appears. The boiler stops heating and the pump is still running. The only

way to stop the locking is by pushing the reset "

B" button.

°C

30 – 80

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Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 17

Page 18

Symptoms5

box 20 Display codes

Display indication

Display

code

Key to display code

[//]

[//)

Standby Hot water mode to “warm start”. box 21

C [0h]

Standby Applies to boilers with hot water supply,

C [0h]

C [0h] C:-h. C:=h)

C[0a]

C[0c]

C[0e]

C[0h]

C[0l]

C[0u]

C[0y]

?1c]

C[2f]

1) This error code may deactivate again automatically after a specific time (without reset). Heating and hot water are now available once more.

2) In the event of this malfunction, the pump is started up and remains in continuous operation in order to minimise the possibility of the heating system freezing up.

Standby Applies to boilers with hot water supply,

Operating phase: The boiler is in heating mode.

Operating phase: The boiler is in hot water mode. The symbol “ G ” lights up.

Operating phase: Pump over-run time via the external cylinder/hot water heater. The symbol “ G “ is off.

Operating phase: The switch optimisation program is activated. This program is activated if there is, more frequently than once every 10 minutes, a heating water requirement from an RC or ON/OFF control signal. This means that the boiler cannot be restarted until at least 10 minutes have elapsed since initial startup of the burner.

Pre-operative phase: The boiler prepares for burner startup whenever a heating requirement or hot water requirement arises.

Ready for operation: The boiler is in ready mode. There is a current heat requirement, but too much energy has been supplied.

Standby for operation: The boiler is in ready mode. There is no current heat requirement.

Ignition phase: The gas valve is activated.

Startup phase: The boiler starts up after activation of the mains power supply or completion of a system reset. This code is displayed for a maximum of 4 minutes.

Operating phase: The flow sensor has detected that the current CH flow temperature is higher than the temperature entered at the control unit, or that it is higher than the CH flow temperature calculated according to heating requirements, or that it is higher than the CH flow temperature calculated for the purposes of hot water supply.

Fault: The flow sensor or safety sensor has detected that the current CH flow temperature is higher than 95°C.

Fault: The flue-gas STL (fume-monitoring device) has detected a temperature higher than 105°C. The flue-gas STL is opened.

Fault: The flow sensor and safety sensor have, after burner startup, not detected any temperature increase in the heating water, or they have determined that the temperature difference between The flow sensor and safety sensor is too high.

Reset

required?

Yes

Other symptoms

No indication on DBA control panel display. box 21

No (or insufficient) hot water, radiators, convectors, etc. may be heated without current heat requirement.

hot water available, no heating operation. Applies to boilers without hot water supply,

no heating operation.

hot water available, no heating operation.

The heating circuit is warmed up without a heat requirement.

Pump over-run time: Heating system factory default setting = 5 minutes; for details of hot water and service mode see box 5.

The target room-temperature may not be reached. box 25

Heat request, but no respons of the boiler box 285

Recycling phase: The fan runs for 15 seconds at about 60% of maximum speed.

"Extraction of residual fumes in boiler"

The target room-temperature may not be reached. box 26

The target room-temperature may not be reached. box 27

No heating operation and no hot water. box 28

Diagnosis

box 22

box 23

box 24

box 22

box 27

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18 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

Page 19

box 20 Display codes

Symptoms 5

Display indication

Display

code

C[2p]

C[3a]

?3l]

?3y]

?4a]

?4e]

?4l]

?4p]

C[6a]

?6a]

:6c]

?6c]

C[6l]

?7c]

!88|

?9a]

?9f]

?9h]

Key to display code

Fault: The flow sensor has detected a temperature increase, in the heating system water, of over 5 °C/sec.

Fault: The tacho signal from the fan has failed during the operating phase.

Fault: The tacho signal from the fan is not present during the preoperative or operating phase.

Fault: No current of air after a certain time.

Fault: The fan runs too slowly or too fast.

Fault: The flow sensor and safety sensor have detected a CH flow temperature of over 105 °C.

Fault: The sensor test has failed.

Fault: The contacts of the flow sensor and safety sensor are shorted to each other, or there is a short-circuit to earth (ground), or the flow or safety sensor has detected a CH flow temperature of above 130 °C.

Fault: The contacts of the flow sensor or safety sensor are broken.

Fault: During the ignition phase, the system has detected an insufficient ionisation current.

Fault: After four startup attempts, the system has detected an insufficient ionisation current.

Fault: The system has detected an ionisation current before burner startup.

Fault: An ionisation current has been measured as soon as the burner shuts down.

Fault: The flame goes out during the operating phase.

Fault: The power supply was shut off during a crucial breakdown.

Operating phase: Display test during startup phase: The code is displayed for a maximum of 1 second.

Fault: The DBA control panel is defective.

Fault: The contacts of the gas valve have been broken.

Fault: The DBA control panel is defective.

Reset

required?

Yes2)No heating operation and no hot water. box 29

Yes2)No heating operation and no hot water. box 30

Yes2)No heating operation and no hot water. box 31

Yes

Yes2)No heating operation and no hot water. box 33

Yes

Yes2)No heating operation and no hot water. box 35

Yes

Yes2)No heating operation and no hot water. box 38

Yes2)No heating operation and no hot water. box 39

Yes2)No heating operation and no hot water. box 41

Yes2)No heating operation and no hot water. box 40

Yes2)No heating operation and no hot water. box 41

Other symptoms

No heating operation and no hot water. box 32

No heating operation and no hot water. box 34

No heating operation and no hot water. box 36

No heating operation and no hot water. box 37

Diagnosis

box 27

box 29

box 36

?9l]

1) This error code may deactivate again automatically after a specific time (without reset). Heating and hot water are now available once more.

2) In the event of this malfunction, the pump is started up and remains in continuous operation in order to minimise the possibility of the heating system freezing up.

Fault: The contacts of the gas valve have been broken.

Fault: The DBA control panel is defective.

Yes2)No heating operation and no hot water. box 40

Yes2)No heating operation and no hot water. box 41

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Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 19

Page 20

Symptoms5

box 20 Display codes

Display indication

Display

code

?9p]

?9y]

?ef]

?e1]

Key to display code

Fault: The DBA control panel is defective.

Fault: Short circuit in the gas valve.

Fault: The contacts of the KIM (EEPROM on the DBA control panel circuit board) may be loose or short-circuited.

Fault: The DBA control panel is defective.

Reset

required?

Yes2)No heating operation and no hot water. box 41

Yes box 41

Yes2)No heating operation and no hot water. box 41

Other symptoms

No heating operation and no hot water. box 41

?e4] ?ea] ?ec]

Fault:

C[re]

1) This error code may deactivate again automatically after a specific time (without reset). Heating and hot water are now available once more.

2) In the event of this malfunction, the pump is started up and remains in continuous operation in order to minimise the possibility of the heating system freezing up.

Reset is carried out. This code appears after the reset button 5 seconds.

B is pressed for

Applies only to a system-blocking error (flashing display code)

Diagnosis

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20 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

Page 21

6 Diagnosis

box 21

Diagnosis 6

[\/\/\|

step 1 Check to ensure that the power supply cable to the mains switch box has been installed correctly.

step 2 Is the power supply cable to the mains switch box correctly installed? Yes: → step 4

step 3 Install the power supply cable correctly, see box 54. → box 42

step 4 Check to ensure that the operating switch on the boiler DBA control panel is set to position “1” as per box 55.

step 5 Is the operating switch on the boiler DBA control panel set to “I” (ON)? Yes: → step 7

step 6 Turn the operating switch on the DBA control panel of the boiler to position “1” (ON), see box 55. → box 42

step 7 Check to the ensure that there is a 230V AC power supply at the mains switch.

step 8 Is there a 230V AC supply at the mains switch? Yes: → step 10

step 9 Deal with any problem in the electrical system. → box 42

step 10 Measure the resistance of the 230V AC power supply cable.

step 11 Is the resistance of the 230V AC power supply cable within the specified limits? Yes: → step 22

step 12 Replace the cable loom (or the affected part thereof). → box 42

step 13 Use a multimeter to check the fuse on the inside of the DBA control panel, see box 62 to 65.

step 14 Is the fuse working correctly? Yes: → box 41

step 15 Replace fuse, see box 62.

step 16 Is there any indication on the DBA control panel display? Yes: → box 42

step 17 Turn the operating switch on the DBA control panel of the boiler to position “0” (OFF), see box 43.

step 18 Disconnect the following boiler components from the electrical power supply:

step 19 Check the fuse again for correct functioning. Use a multimeter to check the fuse on the inside of the DBA

step 20 Is the fuse working correctly? Yes:

step 21 Replace fuse again, see box 62.

step 22 Turn the operating switch on the DBA control panel of the boiler to position “1” (ON), see box 55.

step 23 Is there any indication on the DBA control panel display? Yes:

step 24 Use a multimeter to check the power supply cables of the pump (box 95), the fan (box 69) and the glow ignitor

step 25 Are the cables in order? Yes: → step 27

step 26 Replace the cable harness (or the affected part thereof).

step 27 Turn the operating switch on the DBA control panel of the boiler to position “0” (OFF), see box 43.

step 28 Connect the power supply plug of the pump in reverse.

step 29 Turn the operating switch on the DBA control panel of the boiler to position “1” (ON), see box 55.

No indication on DBA control panel display.

– pump, see box 92 – fan, see box 71, item 1.

control panel, see box 62.

(box 137) for signs of short circuiting.

Replace fuse again, see box 62.

No: → step 3

No: → step 6

No: → step 9

No: → step 21

No: → step 15

No: → step 17

→ step 22

No:

→ step 21

→ step 27

No: → step 24

No: → step 26

→ box 42

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Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 21

Page 22

Diagnosis6

box 21

step 30 Is there any indication on the DBA control panel display? Yes: → step 33

No: → step 31

step 31 Replace the pump, see box 101.

step 32 Replace fuse again, see box 62. → step 33

step 33 Turn the operating switch on the DBA control panel of the boiler to position “0” (OFF), see box 43.

step 34 Connect the power supply plug of the fan in reverse.

step 35 Turn the operating switch on the DBA control panel of the boiler to position “1” (ON), see box 55.

step 36 Is there any indication on the DBA control panel display? Yes: → box 42

step 37 Replace fan, see box 76. → step 38

step 38 Replace fuse again, see box 62.

box 22

No (or insufficient) hot water, radiators, convectors, etc. may be heated without current heat requirement.

step 1 Set the operating switch on the boiler DBA control panel to position “0“ (OFF), see box 43, and set the other

DBA control panel operating switch to position “1“ (ON), see box 55.

step 2 Open a hot water tap.

step 3 Check that the hot water pipe directly beneath the (external) storage-type water heater warms up.

step 4 Does the pipe warm up (to approx. 60 °C)? Yes:

step 5 The cause of this fault does not lie with the boiler, but with the mains water supply. Check to see if the

MCW inlet and DHW outlet have been incorrectly connected to the (external) storage-type water heater.

step 6 Are the pipes connected correctly? Yes:

step 7 Connect the pipeworks correctly.

step 8 Close the shut-off valve in the MCW inlet and open a hot water tap at random to see if water is still flowing.

step 9 Is this the case? Yes:

step 10 The cause is a defective (thermostat-controlled) mixer tap, a thermostat-controlled mixer valve or a short

circuit between the hot- and cold water circuits.

step 11 Check to see if any other external part of the drinking-water system is a possible cause.

step 12 Are such items detected? Yes:

step 13 Place the affected components out of service.

step 14 Check

to ensure that the pre-adjusted setting corresponds to the hot water to ensure that the DHW temperature is adjusted to a high enough setting, see box 61. to see if the hot water supply has been shut off by the control system (ModuLink 250 RF).

step 15 Are the adjustment settings in order? Yes:

step 16 Adjust the settings. step 17 Check to see if the “hot water mode” indicator (H) or (I) lights up on the display, see box 11. step 18 Does the “hot water mode” indicator (H) or (I) light up? Yes:

step 19 Check the turbine flow-meter, see box 104, or DWH temperature sensor of any external storage-type water

heater that might be fitted.

[60) box 14 supply.

→ step 32

No: → step 37

→ box 42

→ step 5

No: → step 39

→ step 8

No:

→ step 7

→ box 42

→ step 10

No:

→ step 11

→ box 42

→ step 13

No:

→ box 42

→ step 17

No:

→ step 16

→ box 42

→ step 25

No: → step 19

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22 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

Page 23

Diagnosis 6

box 22

step 20 Is the turbine flow-meter working correctly (along with DHW temperature sensor of any external storage-type

water that might be fitted)?

step 21 Replace the turbine flow-meter, or DHW temperature sensor of any external storage-type water heater that

might be fitted.

step 22 Check the cable of the turbine flow-meter, see box 112, or cable of the DHW temperature sensor of any

external storage-type water heater that might be fitted.

step 23 Is the cable correctly connected and free of damage? Yes:

step 24 Replace the cable loom (or the affected part thereof).

step 25 Check to ensure that the boiler starts up to supply hot water, see box 15.

step 26 Does the boiler start up? Yes:

step 27 Interpret current display codes box 20 and deal with fault.

step 28 Check to ensure that the tap flow rate is correctly adjusted, see box 180.

step 29 Is the tap flow rate correctly adjusted? Yes:

step 30 Correctly adjust the tap flow rate, see box 180.

step 31 Is an internal 3-way valve fitted? Yes:

step 32 Check the movement of the servomotor of the Buderus 24V AC external 3-way valve, see box 211.

step 33 Does the servomotor of the Buderus 24V AC external 3-way valve move correctly? Yes:

step 34 Check the movement of the servomotor of the internal 3-way valve, see box 181..

step 35 Does the servomotor of the internal 3-way valve move correctly? Yes:

step 36 Check to ensure that the the Buderus 24V AC external 3-way valve has been fitted correctly,

see box 227.

step 37 Has the Buderus 24V AC external 3-way valve been fitted correctly? Yes:

step 38 Fit the Buderus 24V AC external 3-way valve in the correct way, see box 227.

step 39 Check the drive mechanism of the internal 3-way valve, see box 195.

step 40 Is the drive mechanism of the internal 3-way valve working correctly? Yes:

step 41 Replace the drive mechanism of the internal 3-way valve, see box 198.

step 42 Check the circulation for debris, see box 97.

step 43 Is there any debris in the pump? Yes:

step 44 Clean the pump, see box 97. → box 42

step 45 The following components must be checked for soiling and/or damage:

- combustion-air inlet pipework

- heat exchanger

- flue-gas pipework.

step 46 Are the above-mentioned components clean and free of damage? Yes:

step 47 Clean and/or replace the corresponding components.

Yes: → step 22

No:

→ step 21

→ box 42

→ box 41

No:

→ step 24

→ box 42

→ step 28

No:

→ step 27

→ box 42

→ step 31

No:

→ step 30

→ step 34

No:

→ step 32

→ step 36

No:

→ step 63

→ step 39

No:

→ step 57

→ step 69

→ step 38

No:

→ box 42

→ step 42

No:

→ step 41

→ box 42

→ step 44

No:

→ step 45

→ step 48

No: → step 47

→ box 42

We reserve the right to make technical modifications Buderus Ltd. • http://www.buderus-domestic.co.uk

Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 23

Page 24

Diagnosis6

box 22

step 48 Check the standing and working gas pressures, see box 230.

step 49 Are the standing and working pressures correct? Yes:

step 50 If the standing and working gas input pressures are not detected, consult your gas utility company. → box 42

step 51 Check the gas/air ratio, see box 233.

step 52 Is the gas/air ratio correct? Yes:

step 53 Adjust the gas/air ratio, see box 233.

step 54 Check the plate heat exchanger or the external hot water cylinder for furring.

step 55 Is the plate heat exchanger or hot water cylinder furred up? Yes:

step 56 Decalcify the plate heat exchanger and/or hot water cylinder, see from box 269.

step 57 3-way valve: Check the startup of the servomotor of the internal 3-way valve, see box 181 and box 185.

step 58 Does the servomotor of the internal 3-way valve start up correctly? Yes:

step 59 Replace the servomotor of the internal 3-way valve, see box 190.

step 60 Check the wiring of the internal 3-way valve, see box 191.

step 61 Is the cable correctly connected and free of damage? Yes:

step 62 Replace the cable loom (or the affected part thereof). → box 42

step 63 Check to ensure that the Buderus 24V AC external 3-way valve has actuated correctly,

see box 212 and box 228 parts 1 and 2.

step 64 Does the Buderus 24V AC external 3-way valve actuate correctly? Yes:

step 65 Replace the servomotor of the Buderus 24V AC external 3-way valve, see box 217.

step 66 Check the wiring of the Buderus 24V AC external 3-way valve, see box 220.

step 67 Is the wiring of the Buderus 24V AC external 3-way valve in correct condition? Yes:

step 68 Replace the wiring of the Buderus 24V AC external 3-way valve.

step 69 Check the drive mechanism of the Buderus 24V AC external 3-way valve, see box 221.

step 70 Is the drive mechanism of the Buderus 24V AC external 3-way valve working correctly? Yes:

step 71 Replace the drive mechanism of the Buderus 24V AC external 3-way valve, see box 221.

step 72 Check the wiring of the Buderus 24V AC external 3-way valve between the connection box or moving plug-

and-socket connection and the motor of the Buderus 24V AC external 3-way valve, see box 287.

step 73 Is the wiring in order? Yes:

step 74 Replace the cable loom (or the affected part thereof).

box 23

On combi boilers: hot water available, but no heating operation. On system boilers: no heating operation.

Hot water may be available, but no heating operation.

step 1 Check to ensure that the power supply cable to the mains switch box has been installed correctly, see box 54.

→ step 51

No:

→ step 50

→ step 54

No: → step 53

→ box 42

→ step 56

No:

→ box 41

→ box 42

→ step 59

No:

→ step 60

→ box 42

→ box 41

No:

→ step 62

→ step 65

No:

→ step 66

→ box 42

→ step 71

No:

→ step 68

→ box 42

→ step 42

No: → step 71

→ box 41

No:

→ step 74

→ box 42

We reserve the right to make technical modifications Buderus Ltd. • http://www.buderus-domestic.co.uk

24 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

Page 25

Diagnosis 6

box 23

step 2 Check to ensure that the preset room temperature or heating configuration of the Buderus controls or ON/

OFF controller has been adjusted to a high enough setting (see operating instructions).

step 3 Is the preset room temperature or heating configuration of the Buderus controls or ON/OFF controller

adjusted to a high enough setting?

step 4 Adjust the preset room temperature controller or heating configuration of the Buderus controls or

ON/OFF controller to a higher setting (see operating instructions).

step 5 Check to see if the “heating requirement” (K) indicator lights up on the display, see box 11. step 6 Does the “heating requirement” (K) indicator light up? Yes:

step 7 Check the Buderus controls or ON/OFF controller as per box 177.

step 8 Is the Buderus controls or ON/OFF controller working correctly? Yes:

step 9 Replace the thermostat cable.

step 10 Replace the Buderus controls or ON/OFF controller. → box 42

step 11 Check to ensure that the CH flow temperature at the DBA control panel or on the Buderus controls or ON/

OFF controller is adjusted to a high enough setting as per box 14 and box 61 .

step 12 Is the CH flow temperature adjusted to a high enough setting? Yes:

step 13 Are enough thermostatic valves open on the radiators, convectors, etc? Yes:

step 14 Open more thermostatic valves on the radiators, convectors, etc.

step 15 Adjust the CH flow temperature as per box 14 and box 61. Ensure that the Buderus controls or

ON/OFF controller are calling for a heating demand.

step 16 Check to ensure that the CH flow temperature is correctly adjusted, see box 14.

step 17 Is the CH flow temperature adjusted to a high enough setting? Yes:

step 18 Adjust the CH flow temperature to a higher setting, see box 14.

step 19 Is the CH flow temperature of the boiler sufficient to heat the building? Yes:

step 20 Install a larger boiler.

step 21 Is there a hot water supply? Yes:

step 22 Is an internal 3-way valve fitted? Yes:

step 23 Check the movement of the servomotor of the internal 3-way valve, see box 181.

step 24 Does the servomotor of the internal 3-way valve move correctly? Yes:

step 25 Check the drive mechanism of the internal 3-way valve, see box 195.

step 26 Is the drive mechanism working correctly? Yes:

step 27 Replace the drive mechanism of the internal 3-way valve, see box 198. → box 42

step 28 Check the actuation of the servomotor of the internal 3-way valve, see box 185.

step 29 Does the servomotor of the internal 3-way valve start up correctly? Yes:

Yes:

→ step 5

No: → step 4

→ box 42

→ step 11

No:

→ step 7

→ step 9

No:

→ step 10

→ box 42

→ step 13

No:

→ step 15

→ step 16

No: → step 14

→ box 42

→ step 19

No: → step 18

→ box 42

→ step 21

→ step 20

No:

→ box 42

→ step 22

No: → box 41

→ step 23

No:

→ step 34

→ step 25

No:

→ step 28

→ box 42

No:

→ step 27

→ step 30

No: → step 31

We reserve the right to make technical modifications Buderus Ltd. • http://www.buderus-domestic.co.uk

Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 25

Page 26

Diagnosis6

box 23

step 30 Replace the servomotor of the internal 3-way valve, see box 190. → box 42

step 31 Check the power supply cable of the internal 3-way valve, see box 191.

step 32 Is the power supply cable of the internal 3-way valve in good condition? Yes:

step 33 Replace the cable loom (or the affected part thereof).

step 34 Check the movement of the servomotor of the Buderus 24V AC external 3-way valve, see box 211.

step 35 Does the servomotor of the Buderus 24V AC external 3-way valve operate correctly? Yes:

step 36 Check to ensure that the the Buderus 24V AC external 3-way valve has been fitted correctly,

see box 227.

step 37 Has the Buderus 24V AC external 3-way valve been fitted correctly? Yes:

step 38 Install the Buderus 24V AC external 3-way valve correctly, see box 227.

step 39 Check to ensure that the Buderus 24V AC external 3-way valve is actuated correctly,

see box 212 and box 228.

step 40 Does the Buderus 24V AC external 3-way valve actuate correctly? Yes:

step 41 Replace the servomotor of the Buderus 24V AC external 3-way valve, see box 217.

step 42 Check the wiring of the Buderus 24V AC external 3-way valve, see box 220.

step 43 Is the wiring of the Buderus 24V AC external 3-way valve in correct condition? Yes:

step 44 Replace the wiring of the Buderus 24V AC external 3-way valve.

step 45 Check the drive mechanism of the Buderus 24V AC external 3-way valve, see box 221.

step 46 Is the drive mechanism of the Buderus 24V AC external 3-way valve working correctly? Yes:

step 47 Replace the internal components of the Buderus 24V AC external 3-way valve, see box 224. → box 42

step 48 Check the wiring of the Buderus 24V AC external 3-way valve between the connection box or moving plug-

and-socket connection and the DBA control panel as per box 287.

box 24

On combi boiler supply: hot water available, but no heating operation. On system boiler supply: no heating operation.

Hot water may be available, but no heating operation.

step 1 Check to ensure that the power supply cable to the RTH converter/Junction box has been installed correctly,

see box 285.

step 2 Is the 230V connection to the RTH converter/Junction box fitted correctly? Yes:

step 3 Correctly attach the switch live to terminal 1 and Neutral to terminal 2 on the 230V connector, see box 285.

step 4 Disconnect black leads from terminals 1 & 2 on the back of the DBA and test for continuity between the two

leads. No continuity check S/L and N connections are made correctly and that there is 230v between the two. Replace RTH converter/Junction box. Continuity reconnect the cables to terminals 1 & 2 and check the connections between the terminals and the DBA.

step 5 Is the volt free connection to the RTH converter/Junction box fitted correctly? Yes:

step 6 Check to ensure that the connections of the external control unit are attached to terminal 1 and 2 of the

connection block, indicated by a clock inside a rectangle, see box 286 and box 285 (item 3).

→ box 41

No: → step 33

→ box 42

→ step 36

No:

→ step 39

→ step 45

No:

→ step 38

→ box 42

→ step 41

No: → step 42

→ box 42

→ step 47

No:

→ step 44

→ box 42

→ box 41

No:

→ step 47

→ step 4

No: → step 3

→ box 42

→ step 6

No: → step 8

We reserve the right to make technical modifications Buderus Ltd. • http://www.buderus-domestic.co.uk

26 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

Page 27

Diagnosis 6

box 24

step 7 Is there a permanent link between terminal 1 and 2 on the volt free connecter? Yes: → step 8

No:

→ step 9

step 8 Check the cable connection between the RTH converter/Junction box and terminal 1 and 2 on the DBA.

step 9 Check the external cable connections and control devices.

step 10 Has the malfunction been repaired? Yes:

box 25

The switch optimisation program is activated. This program is activated if there is,

C [0a]

step 1 Check to ensure that the connections of the control device are correctly fitted at the boiler and control device.

step 2 Is the control device connected correctly? Yes:

step 3 Connect the control device correctly.

step 4 Carry out a visual examination where possible, and use a multimeter to check the electrical resistance of the

thermostat lead. Check for breakages and loose contacts.

step 5 Is the thermostat cable in good condition? Yes:

step 6 Replace the thermostat cable.

step 7 Check to ensure that enough thermostatic valves are open on the radiators, convectors, etc.

step 8 Are enough thermostatic valves open on the radiators, convectors, etc? Yes:

step 9 Open more thermostatic valves on the radiators, convectors, etc.

step 10 Attempt to rectify the fault by temporarily replacing the room thermostat or external temperature-dependent

controller.

step 11 Has the malfunction been repaired? Yes:

box 26

C [0y]

more frequently than once every 10 minutes, a heating water requirement from an Buderus controller or ON/OFF controller signal. This means that the boiler cannot be restarted until at least 10 minutes have elapsed since initial startup of the burner.

Operating code

The flow NTC sensor has detected that the current CH flow temperature is higher than the temperature entered at the control unit, or that it is higher than the CH flow temperature calculated according to heating requirements, or that it is higher than the CH flow temperature calculated for the purposes of hot water supply.

Operating code

→ box 42

No:

→ box 41

→ step 4

No:

→ step 3

→ box 42

→ step 7

No: → step 6

→ box 42

→ step 10

No:

→ step 9

→ box 42

→ box 41

No:

step 1 Check to ensure that the CH flow temperature at the DBA control panel is higher than that entered at the

controller, see box 61.

step 2 Is the CH flow temperature at the DBA control panel adjusted correctly? Yes:

step 3 Adjust the CH flow temperature at the DBA control panel to a higher setting, see box 61.

step 4 Check to ensure that enough thermostatic valves are open on the radiators, convectors, etc.

step 5 Are enough thermostatic valves open on the radiators, convectors, etc? Yes:

step 6 Open more thermostatic valves on the radiators, convectors, etc.

step 7 Check to see if a hot tap or taps have been opened on brief, consecutive occasions.

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Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 27

No:

→ step 4

→ step 3

→ box 42

→ step 7

→ step 6

→ box 42

Page 28

Diagnosis6

box 26

step 8 Have a hot water tap or taps been opened briefly and consectutively on several occasions? Yes: → step 9

No:

→ box 15

step 9 Inform the user that the fault has been caused by opening hot taps on many brief, consecutive occasions.

step 10 Check the electrical resistance of the DHW temperature sensor, see box 104.

step 11 Is the electrical resistance of the DHW temperature sensor in order? Yes:

step 12 Replace the DHW temperature sensor.

box 27

The flow NTC sensor or safety sensor has detected that the current CH flow

C [0y]

C [2f]

C [2p]

temperature is higher than 95 °C.

Blocking boiler-fault code

The flow NTC sensor and safety sensor have not, after burner startup, detected any temperature increase in the heating system water, or the temperature difference between the flow NTC sensor and safety sensor is excessive.

Blocking boiler-fault code

The flow NTC sensor has detected a temperature increase in the heating system water of more than 5 °C/sec.

Blocking boiler-fault code

No:

→ box 42

→ box 41

→ step 12

The flow NTC sensor and safety sensor have detected a CH flow temperature of over

[4a]

[4e]

step 1 Are the servicing valves open? Yes:

step 2 Open the servicing valves, see box 53.

step 3 Is the pressure in the heating system at least 1 bar? Yes:

step 4 Fill and vent the heating system, see box 52.

step 5 Are enough thermostatic valves open on the radiators, convectors, etc? Yes:

step 6 Open more thermostatic valves on the radiators, convectors, etc.

step 7 Check the flow NTC sensor and safety sensor, see box 104.

step 8 Are the flow NTC sensor and safety sensor in order? Yes:

step 9 Replace the flow NTC sensor or safety sensor, see box 116. → box 42

step 10 Check the cable between the flow NTC sensor or safety sensor for short circuits, see box 112.

step 11 Check the pump, see box 89 to 100.

step 12 Is the pump working correctly? Yes:

step 13 Replace the pump, see box 101.

step 14 Check to ensure that the internal by-pass valve in the boiler or the external overflow valve in the heating

system are working correctly. Possible to adjust external overflow valve to max. 25 kPa (if fitted).

step 15 Is the by-pass valve working correctly? Yes:

105 °C.

Locking boiler-fault code

Short circuit between flow NTC sensor or safety sensor.

Locking boiler-fault code

→ step 3

No:

→ step 2

→ step 5

No:

→ step 4

→ step 7

No:

→ step 6

→ box 42

→ step 10

No:

→ step 9

→ step 14

No:

→ step 13

→ box 41

No: → step 14

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28 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

Page 29

Diagnosis 6

box 27

step 16 Replace the by-pass valve. → box 42

box 28

The flue-gas STL (fume-monitoring device) has detected a temperature higher than

[1c]

step 1 Check to ensure that the restrictor baffle has been installed as per box 261, item 1.

step 2 Has the restrictor baffle been fitted? Yes:

step 3 Fit the restrictor baffle, see box 261, item 1.

step 4 Check the entire system of flue gas pipe for restrictions.

step 5 Is the entire system of flue gas pipe in full working order? Yes:

step 6 Deal with restriction.

step 7 Check the flue-gas STL, see box 120.

step 8 Is the flue-gas STL working correctly? Yes:

step 9 Replace the flue-gas STL, see box 129.

step 10 Check the wiring of the flue-gas STL, see box 126.

step 11 Is the wiring of the flue-gas STL in full working order? Yes:

step 12 Replace the cable loom (or the affected part thereof).

box 29

C [3a]

105°C. The flue-gas STL is open.

Locking boiler-fault code

The tacho signal from the fan has failed during the operating phase.

Blocking boiler-fault code

→ step 4

No:

→ step 3

→ box 42

→ step 7

No:

→ step 6

→ box 42

→ step 10

No:

→ step 9

→ box 41

No: → step 12

→ box 42

The tacho signal from the fan is not present during the pre-operative or operating

[3l]

step 1 Check to ensure that both plug-and-socket connections of the fan are correctly fitted, see box 246, item 1.

step 2 Are the plug-and-socket connections fitted correctly? Yes:

step 3 Reconnect the plug-and-socket connection of the fan.

step 4 Check fan, 230V AC supply, see box 66 or box 287.

step 5 Does activation take place correctly? Yes:

step 6 Check the power supply cable of the fan (230V AC), see box 69.

step 7 Is the power supply cable of the fan in full working order? Yes:

step 8 Replace the cable loom (or the affected part thereof).

step 9 Check tacho cable of fan, see box 73.

step 10 Is the tacho cable in full working order? Yes:

step 11 Replace the cable loom (or the affected part thereof).

step 12 Check to ensure that the mains voltage at the earthed (grounded) plug is between 195V and 253V AC.

phase.

Locking boiler-fault code

No:

→ step 4

→ step 3

→ box 42

→ step 9

→ step 6

→ box 41

→ step 8

→ box 42

→ step 12

→ step 11

→ box 42

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Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 29

Page 30

Diagnosis6

box 29

step 13 Is the mains voltage sufficient? Yes: → step 15

No:

→ step 14

step 14 The cause of the fault lies in the electrical system.

step 15 Replace fan, see box 76.

step 16 Has the malfunction been repaired? Yes:

box 30

No current of air after a certain time.

[3l]

step 1 Attempt to rectify the fault by temporarily replacing the fan, see box 76.

step 2 Has the malfunction been repaired? Yes:

box 31

[3y]

Locking boiler-fault code

The fan runs too slowly or too fast.

Locking boiler-fault code

No:

→ box 42

→ box 41

→ box 42

→ box 41

step 1 Check the plug-and-socket connection of the fan tacho cable.

This is the narrow plug, see box 78, item 2.

step 2 Is the plug-and-socket connection in full working order? Yes:

step 3 Reconnect the plug-and-socket connection, see box 78, item 2.

step 4 Check tacho cable of fan, see box 73.

step 5 Is the tacho cable in full working order? Yes:

step 6 Replace the tacho cable.

step 7 Check to ensure that the mains voltage at the earthed (grounded) plug is between 195V and 253V AC.

step 8 Is the mains voltage sufficient? Yes:

step 9 The cause of the fault lies in the electrical system. → box 42

step 10 Check to see if there is a restriction in the fan, burner, heat exchanger or flue-gas system.

step 11 Is there a restriction? Yes:

step 12 Deal with restriction.

step 13 Check to see if there is a second fan in the flue gas pipe or air inlet system.

step 14 Is a second fan fitted? Yes:

step 15 Take second fan out of service.

step 16 Check to see if the fan impeller has come loose at the motor spindle, see box 76.

step 17 Has the fan come loose? Yes:

step 18 Replace fan, see box 76.

step 19 Has the malfunction been repaired? Yes:

→ step 4

No:

→ step 3

→ box 42

→ step 7

No:

→ step 6

→ box 42

→ step 10

No:

→ step 9

→ step 12

No: → step 13

→ box 42

→ step 15

No:

→ step 16

→ box 42

→ step 18

No:

→ step 19

→ box 42

No:

→ box 41

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30 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

Page 31

Diagnosis 6

box 32

The flow NTC sensor has detected a temperature of over 105 °C.

[4a]

step 1 Check the flow rate in the heating circuit.

step 2 Are all servicing valves and thermostat valves closed? Yes: → step 4

step 3 Check all servicing valves and thermostat valves for correct functioning

step 4 Open all servicing valves and thermostat valves.

step 5 Has the malfunction been repaired? Yes:

box 33

[4e]

step 1 Check the flow NTC sensor and safety sensor and their wiring for short circuits, see box 104 to 115 and

box 287.

step 2 Are the flow NTC sensor and safety sensor, along with their wiring, in correct working order? Yes:

step 3 Replace the flow NTC sensor, safety sensor, cable loom or corresponding component of the cable loom,

see box 116.

box 34

[4l]

Locking boiler-fault code

The sensor test has failed.

Locking boiler-fault code

The contacts of the flow NTC sensor and safety sensor are shorted to each other, or there is a short-circuit to earth (ground), or the flow or safety sensor has detected a CH flow temperature of above 130 °C.

Locking boiler-fault code

No: → step 3

→ box 42

No:

→ box 41

No: → step 3

→ box 42

step 1 Are the servicing valves open? Yes:

No:

step 2 Open the servicing valves, see box 53.

step 3 Is the pressure of the heating system water at least 1 bar? Yes:

No:

step 4 Fill and vent the heating system, see box 52.

step 5 Are enough thermostatic valves open on the radiators, convectors, etc? Yes:

No:

step 6 Open more thermostatic valves on the radiators, convectors, etc.

step 7 Check the flow NTC sensor and safety sensor, see box 104.

step 8 Are the flow NTC sensor and safety sensor functioning correctly? Yes:

No: → step 9

step 9 Replace the flow NTC sensor or safety sensor, see box 116.

step 10 Check the cables of the flow NTC sensor and safety sensor, see box 112.

step 11 Are the cables in order? Yes:

No:

step 12 Replace the cable loom (or the affected part thereof).

step 13 Check the pump, see box 89 to 100.

step 14 Is the pump working correctly? Yes:

No:

→ step 3

→ step 2

→ step 5

→ step 4

→ step 7

→ step 6

→ box 42

→ step 10

→ step 13

→ step 12

→ box 42

→ box 41

→ step 15

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Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 31

Page 32

Diagnosis6

box 34

step 15 Replace the pump, see box 101. → box 42

box 35

The contacts of the flow NTC sensor or safety sensor are broken.

[4p]

step 1 Check the flow NTC sensor and safety sensor, see box 104.

step 2 Are the flow NTC sensor and safety sensor functioning correctly? Yes:

step 3 Replace the flow NTC sensor and safety sensor, see box 116.

step 4 Check the cable of the flow NTC sensor and safety sensor, see box 112.

step 5 Are the cables in order? Yes:

step 6 Replace the cable loom (or the affected part thereof).

box 36

C [6a]

Locking boiler-fault code

The system has detected an insufficient ionisation current during the ignition phase.

Blocking boiler-fault code

→ step 4

No: → step 3

→ box 41

No:

→ step 6

→ box 42

The system has detected an insufficient ionisation current after four startup

[6a]

step 1 Is the heating system propane gas-fired? Yes:

step 2 Ensure that no nitrogen remains in the gas tank or gas flow pipes.

You should also consult your gas utility company.

step 3 Check whether the gas tap is open, see box 59.

step 4 Is the gas tap open? Yes:

step 5 Open the gas tap, see box 59. → step 63

step 6 Check the static and working gas pressure, see box 230.

step 7 Are the static and working gas pressures correct? Yes:

step 8 Check to see if there is a restriction in the pipework between the gas tap and gas valve.

step 9 Is there a restriction? Yes:

step 10 Deal with restriction.

step 11 Check for restrictions in the remaining section of the gas flow pipe.

step 12 Is there a restriction? Yes:

step 13 Deal with restriction.

step 14 Has the gas flow pipe been bled of air? Yes: → step 16

step 15 Vent the gas flow pipe of air, see box 239.

step 16 Check to see if the glow ignitor activates with the operating code C [0c], see box 130.

step 17 Does the glow ignitor activate with the operating code

attempts.

Locking boiler-fault code

→ step 2

No: → step 3

→ step 63

→ step 6

No:

→ step 5

→ step 14

No: → step 8

→ step 10

No: → step 11

→ step 63

→ step 13

No:

→ step 38

→ step 63

No:

→ step 15

→ step 62

C [0c]?Yes:→ step 21

No:

→ step 18

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32 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

Page 33

Diagnosis 6

box 36

step 18 Check the power supply cable of the glow ignitor, see box 137.

step 19 Is the power supply cable in full working order? Yes:

step 20 Replace the cable loom (or the affected part thereof). → step 62

step 21 Check the electrical resistance of the glow ignitor, see box 134.

step 22 Is the electrical resistance of the glow ignitor in order? Yes:

step 23 Replace the glow ignitor, see box 140.

step 24 Place the boiler in full-load operation, see box 13, and check whether the glow ignitor activates with the

step 25 Does the glow ignitor activate with the operating code

step 26 Connect a digital pressure gauge, see box 233 and 234. Open the gas cock and place the boiler into

step 27 Does the gas valve open with the operating code

step 28 Check the plug-and-socket connection on the gas valve, see box 161.

step 29 Is the plug-and-socket connection in full working order? Yes:

step 30 Reconnect the plug-and-socket connection at the gas valve. → step 62

step 31 Check whether the gas valve receives power with the operating code

step 32 Does the gas valve receive power? Yes:

step 33 Replace the gas valve, see box 174.

step 34 Check the power supply cable of the gas valve, see box 167.

step 35 Is the wiring in order? Yes:

step 36 Replace the cable loom (or the affected part thereof).

step 37 Check whether the incoming gas supply is of sufficient capacity.

step 38 Is the incoming gas supply of sufficient capacity? Yes:

step 39 Upgrade internal pipe work. → step 62

step 40 Consult your gas utility company accordingly.

step 41 Measure the gas/air ratio during the startup phase, see box 233.

step 42 Is the gas/air ratio correctly adjusted? Yes:

step 43 Adjust the gas/air ratio, see box 233.

step 44 Check to ensure that the correct gas injector, see box 83, item 1, and the correct Venturi,

step 45 Is the correct gas injector and Venturi fitted? Yes:

step 46 Fit the correct gas injector and/or Venturi, see box 5.

operating code

operation, see box 59 or box 13. Check whether the gas valve opens with the operating code

see box 87, item 1, are fitted as specified. See also box 5.

C [0c] .

C [0c] ?Yes:→ step 26

C [0l] ?Yes:→ step 41

C [0l] , see box 164.

C [0l] .

→ box 41

No:

→ step 20

→ step 24

No: → step 23

→ step 62

No:

→ step 23

No:

→ step 28

→ step 31

No:

→ step 30

→ step 33

No: → step 34

→ step 62

→ box 41

No:

→ step 36

→ step 62

→ step 40

No:

→ step 39

→ step 62

→ step 44

No:

→ step 43

→ step 62

→ step 47

No: → step 46

→ step 62

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Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 33

Page 34

Diagnosis6

box 36

step 47 The following components must be checked for soiling, damage and/or correct installation:

– condensate trap and syphon, see box 256 – combustion-air inlet pipework – air silencer pipework – seal between the Venturi and fan – Venturi, see box 86 – gas injector, see box 83, item 1 – fan – connection between the fan and burner – burner – heat exchanger – system of flue-gas pipe and air inlet pipeworks – pressure control valve, see box 85 – earth (ground) lead of ionisation circuit, see box 160.

step 48 Are the above-mentioned components clean, free of damage and/or correctly intalled? Yes:

step 49 Clean, replace and/or correctly install the components concerned.

step 50 Measure the ionisation current, see box 143.

step 51 Is the ionisation current in order? Yes:

step 52 Check the plug-and-socket connection between the ionisation electrode and cable loom, see box 144.

step 53 Is the plug-and-socket connection in full working order? Yes:

step 54 Correctly insert the plug into its socket → step 62

step 55 Check the cable of the ionisation electrode, see box 151.

step 56 Is the wiring in order? Yes:

step 57 Replace the cable loom (or the affected part thereof).

step 58 Check the ionisation electrode and replace as required, see box 155.

step 59 Temporarily disconnect the flue-gas pipework from the top of the boiler.

Run the boiler at low mode, see box 13. Check to see if the fault has been rectified.

step 60 Has the malfunction been repaired? Yes:

step 61 The cause of the fault lies in the flue-gas system. Take the boiler out of operation.

step 62 Switch the boiler off and then on again at the operating switch.

step 63 Is the error code still displayed? Yes:

step 64 Has an error

step 65 Interpret the display code with box 20 and deal with the fault.

step 66 Has the entire table box 36 been covered? Yes:

C [6a] reoccurred? Yes: → step 66

→ step 50

No:

→ step 49

→ step 62

No:

→ step 52

→ step 55

No:

→ step 54

→ step 58

No: → step 57

→ step 62

→ step 61

No: → step 62

→ box 42

→ step 64

No:

→ box 42

No: → step 65

→ box 41

→ step 1

No:

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34 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

Page 35

box 37

:6c]

Diagnosis 6

The system has detected an ionisation current before burner startup.

Locking boiler-fault code

step 1 Is the ionisation current displayed? Yes:

step 2 Disconnect the plug-and-socket connection, see box 144.

step 3 Is the ionisation current still displayed? Yes:

step 4 Check the plug-and-socket connection between the ionisation electrode and cable loom, see box 144.

step 5 Is the plug-and-socket connection in full working order? Yes:

step 6 Correctly insert the plug into its socket. → step 11

step 7 Check the cable of the ionisation electrode, see box 151.

step 8 Is the wiring in order? Yes:

step 9 Replace the cable loom (or the affected part thereof).

step 10 Check the ionisation electrode, see box 149 or box 155.

step 11 Is the ionisation electrode working correctly? Yes: → step 14

step 12 Replace the ionisation electrode, see box 155.

step 13 Switch the boiler off and then on again at the operating switch.

step 14 The following components should be checked for soiling, damage and/or correct installation:

- syphon, see box 256

- flue-gas pipework.

step 15 Check the pressure control valve, see box 85.

step 16 Is the pressure control valve working correctly? Yes:

step 17 Replace or clean the pressure control valve, see box 85.

box 38

An ionisation current has been measured as soon as the burner shuts down.

[6c]

Locking boiler-fault code

→ step 2

No:

→ step 1

→ step 12

No:

→ box 41

→ step 7

No:

→ step 6

→ step 10

No: → step 9

→ step 13

→ box 42

No:

→ step 12

→ box 42

→ box 41

No:

→ step 17

→ box 42

step 1 Connect a digital pressure gauge, see box 233 and 234. Open the gas cock and place the boiler into full-load

operation, see box 59 or box 13. Deactivate the heat requirement as per flue-gas test (box 13), and check to see if the burner remains under pressure after the “heat requirement” symbol on the DBA control panel goes out.

step 2 Is the burner still under pressure? Yes:

step 3 Check the ionisation electrode, see box 37.

step 4 Close the gas cock, see box 46. Remove the digital pressure gauge and close the burner-pressure

connection nipple. Open the gas cock, see box 59, and run the boiler at full load once more, see box 59 or box 13. Deactivate heat requirement, see box 13, and check to see if the gas valve is still powered after the “heat requirement” indicator goes out, see box 165, item 1 and 2.

step 5 Is the gas valve still powered? Yes:

step 6 Replace the gas valve, see box 174.

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Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 35

→ step 4

No:

→ step 3

→ box 41

No: → step 6

Page 36

box 39

Diagnosis6

[7c]

The power supply was shut off during operation.

Locking boiler-fault code

step 1 Reset the boiler with button "

step 2 Is the error code still displayed? Yes:

step 3 Interpret the fault code now displayed in box 20 and deal with the malfunction.

box 40

The contacts of the gas valve have been broken.

[9f]

Locking boiler-fault code

B", or by turning the operating switch to "OFF" and then "ON" again.

No:

→ step 3

→ box 42

[9l]

step 1 Check the plug-and-socket connection of the gas valve, see box 161.

step 2 Is the plug-and-socket connection in full working order? Yes:

step 3 Reconnect the plug-and-socket connection, see box 161.

step 4 Measure the cable between the gas valve and DBA control panel, see box 164.

step 5 Is the cable correctly connected and free of damage? Yes:

step 6 Replace the cable loom (or the affected part thereof). → box 42

step 7 Measure the resistance of the gas valve coils, see box 171.

step 8 Is the resistance correct? Yes:

step 9 Replace the gas valve, see box 174.

box 41

Bad electrical contacts, circuit board or EEPROM (KIM) of DBA control panel defective.

step 1 Check the contacts on the circuit board of the DBA control panel by pushing fully home the plug-and-socket

connections on the board; check and deal with any other contact problems with plug-and-socket connections.

step 2 Switch the boiler off and then on again at the operating switch.

step 3 Is same fault warning message still displayed? Yes:

step 4 Check the plug-and-socket connection on the EEPROM (KIM), see box 284.

step 5 Has the DBA control panel been replaced? Yes:

step 6 Replace the DBA control panel, see box 281. → step 2

step 7 Contact Buderus (see on the back of this manual).

step 8 Has a new fault occurred? Yes:

step 9 Interpret the fault code now displayed in box 20 and deal with the malfunction.

→ step 4

No:

→ step 3

→ box 42

→ step 7

No:

→ step 6

→ box 41

No: → step 9

→ box 42

→ step 4

No:

→ step 8

→ step 7

No:

→ step 6

→ step 9

No: → box 42

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36 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

Page 37

Diagnosis 6

box 42

step 1 Fit the casing to the boiler.

step 2 Turn the mains switch on the DBA control panel of the boiler to position “0” (OFF), see box 43.

step 3 Turn the mains switch on the DBA control panel of the boiler to position “1” (ON), see box 55.

The fault is now rectified.

Your Buderus 500 should be working now.

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Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 37

Page 38

Actions7

7Actions

box 43 Shutting down

z Turn the mains switch on the boiler to position “0” (OFF,

item 1).

box 46

box 44

OFF

permanent

live

z Turn the mains switch to “OFF”.

box 45

z Close the gas cock (item 1).

box 47 Removal of casing

z Use a radiator key to turn the casing lock to “open”, then

remove casing.

box 48 Draining the system

Key to terms (see box 4): 1 = CH flow

2 = DHW outlet (combination boilers only) 3 = Gas connection 4 = MCW inlet (combination boilers only) 5 = CH return

z Close the servicing valves (item 6), if fitted.

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38 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

z Take the boiler out of operation, see box 43, 44, 45, 46

or 47.

Page 39

Actions 7

box 49

z Loosen by one turn the sealing cap on the automatic air

vent located on the top left-hand part of the boiler.

box 50

box 52 Filling the system and venting it of air

z Turn the operating switch on the boiler to position “0”

(OFF), see box 43.

z Remove casing, see box 47.

box 53

DHW

cold

stop

valve

double

check

valve

filling loop

stop

valve

return

z Connect filling loop (accessory), see box 50, item 6. z Open both stop valves. z Fill the system to a pressure of approx. 1.5 bar. z Shut both stop valves. z Disconnect the filling loop. z Vent all radiators from air starting with the lowest radiator

and working your way up to the highest point.

z Check the pressure after venting. If the pressure has

dropped under 1.0 bar then top up the system as described previously.

z Disconnect the filling loop and cap off.

Key to terms: 1 = CH flow

2 = DHW outlet (combination boilers only) 3 = Gas connection 4 = MCW inlet (combination boilers only) 5 = CH return

z Connect the hose (item 6) to the drain cock of the boiler. z Open the filling and draining cock and drain the heating

system, see

box 53.

box 51

box 54

permanent

live

z Turn the mains switch to “ON”.

z Fit the casing and use the radiator key to turn the casing

lock to “closed”.

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Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 39

Page 40

Actions7

box 55

z Turn the operating switch on the boiler to position “1”

(ON, item 1).

box 56

z Fill the heating system to a pressure of approximately

1.5 bar, then close the filling loop.

z Vent all the air vent points in the heating system, working

from bottom to top, in order to allow all air in the heating system to escape.

box 57

box 58

z Vent the pump.

ACAUTION!

Correct venting of the pump will help ensure that it runs for its specified service life. The sliding bearing, which is located behind the vent screw, is lubricated with heating system water.

z Once the heating system has been completely purged of

air, check the pressure at the analogue pressure gauge. If the pressure is lower than 1.0 bar, the boiler should be topped up as described above.

z Close the water tap.

In the case of system boilers:

z Close the filling loop of the boiler, see box 50, item 2. z Remove the hose. z Fit the sealing cap to the filling and draining cock.

In the case of combination boilers:

z Close the filling loop. z Remove the hose.

z Fit casing, see box 51. z Configure target adjustments using the “Settings” menu

on the DBA control panel of the boiler, see box 61

z Loosen by two turns the vent screw (item 1) on the front of

the pump.

ACAUTION!

Water will also squirt out!

box 59 Initial startup

z Open the gas tap (item 2).

box 60

z Put the boiler into operation, see box 53, 54 or 55.

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40 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

Page 41

Actions 7

box 61

z Press the menu button (item 1) on the DBA control panel

of the boiler.

z Configure the menu as required, see box 14.

box 62 Check/replace fuses (1)

HDANGER OF FATAL ACCIDENT

due to electric shock

z Take the boiler out of operation, see box 43, 44 or 47.

box 63

box 64

z Remove the rear section of the DBA control panel,

see box 70.

z Remove the fuse from the fuse holder. z Check the fuse with a multimeter. If the fuse possesses

infinitely high electrical resistance, it is defective.

z Replace the defective fuse with a (new) 2.5 AT slow blow

reserve fuse.

box 65

z Refit the DBA control panel, following the above

procedure in reverse order.

z Refit the casing and place the boiler into operation,

see box 51, 53, 54 or 55.

z Remove the casing from the boiler, see box 47. z Loosen the cap screw on the DBA control panel (item 1). z Tip the DBA control panel forwards (item 2).

box 66 Check fan – activation 230V AC

HDANGER OF FATAL ACCIDENT

due to electric shock

ACAUTION!

To prevent damage, do not insert the measuring electrodes of the multimeter too far into the holes of the plug-and-socket connection.

z Remove the casing and place the boiler out of operation,

see box 47, 43 or 44.

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Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 41

Page 42

Actions7

box 67

z Set the multimeter to VAC. Minimum value: 250 V AC. z Disconnect the 230V AC plug (item 1) from the fan. z Attach the multimeter to the two outer contacts (blue and

brown) of the fan connection plug.

z Start system at full load, see box 54, 55 or 13. z Check whether, with operating code C [0c] active, there

is a voltage of 230 V AC at the two outer contacts (blue and brown) of the plug.

box 70

z Loosen the six screws and remove the rear section.

box 71

Stift 5

Stift 4

JP1

box 68

z Take the electrical system of the boiler out of operation,

box 43 and 44.

see

z Insert the fan connection plug. z Refit the casing and place the boiler into operation, see

box 51, 53, 54 or 55.

box 69 Check fan – power supply cable (230 V AC)

HDANGER OF FATAL ACCIDENT

due to electric shock

ACAUTION!

To prevent damage, do not insert the measuring electrodes of the multimeter too far into the holes of the plug-and-socket connection.

z Take the boiler out of service and tip the DBA control panel

forwards, see

box 43, 44, 47 or 63.

z Disconnect the 230V AC plug (item 1) from the fan. z Set multimeter to “measure resistance”. z Check the power supply cable of the fan for breaks.

The electrical resistance measured at each individual wire must be approximately 0

z Check the power supply cable of the fan for internal short

circuits. The level of electrical resistance, measured between two wires chosen at random, must be infinitely high. See also

box 72

z Insert the fan connection plug. z Refit the DBA control panel, following the above

procedure in reverse order.

z Refit the casing and place the boiler into operation,

see box 51, 53, 54 or 55.

box 287.

Ω.

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42 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

Page 43

Actions 7

box 73 Check fan – tacho cable

HDANGER OF FATAL ACCIDENT

due to electric shock

ACAUTION!

To prevent damage, do not insert the measuring electrodes of the multimeter too far into the holes of the plug-and-socket connection.

z Take the boiler out of service and tip the DBA control panel

forwards, see box 43, 44, 47 or 63.

z Loosen the six screws and remove the rear section,

see box 70.

box 74

box 76 Check fan and/or replace

HDANGER OF FATAL ACCIDENT

due to electric shock

ADANGER OF FATAL ACCIDENT

All work on gas pipework and gas-fitting components must be carried out by a company registered and authorised for this purpose.

INOTE:

Please observe the fitting instructions supplied with the fan.

z Take the boiler out of operation and close the gas tap,

see box 43, 44, 46 or 47.

box 77

JP4

z Pull out the tacho cable plug (item 1). z Set multimeter to “measure resistance”. z Attach the multimeter. z Check the tacho cable of the fan for breaks.

The electrical resistance measured at each individual wire must be approximately 0

z Check the tacho cable of the fan for internal short circuits.

The level of electrical resistance, measured between two wires chosen at random, must be infinitely high.

box 75

z Connect the tacho cable plug. z Refit the DBA control panel, following the above

procedure in reverse order.

z Refit the casing and place the boiler into operation,

see box 51, 53, 54 or 55.

Ω.

JP3

z Pull out the power supply plug of the gas valve (item 1). z Loosen the union nut (item 2). z Detach the air silencer tube (item 3).

box 78

z Pull out both fan plugs (item 2). z Pull out the glow ignitor plug (item 3). z Pull out the ionisation electrode plug (item 1).

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Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 43

Page 44

Actions7

box 79

box 81

z Remove the Venturi (item 1).

box 82

z Fit the Venturi to the new fan.

box 83

z Twist (drawing 1) the fan in the direction of the arrow to

remove (drawing 2).

z Check to see if the fan is soiled or wet. z Check to see if the fan impeller has come loose at the

motor spindle.

box 80

z Loosen the three screws (item 1) on the gas valve. z Remove the gas valve (item 2).

z Fit the gas valve to the new fan. When doing so, ensure

that the gas injector (item

box 84

z Fit the fan to the boiler. Remember to fit the new flat rubber

sealing ring (supplied) when doing so.

z Fit the air silencer tube to the fan. z Fit the gas supply pipe to the gas valve. Ensure when

doing so that the flat rubber sealing ring is correctly fitted.

z Insert the power supply plug into the gas valve, then insert

the power supply plug and tacho cable plug into the fan.

z Open the gas cock and place the electrical system of the

boiler into operation, see box 59, 54 or 55.

z Carry out a gas-leak check. Check the tightness of all

components that were loosened in the course of component removal. Use an authorised foam-type leak detection product for this purpose. If you detect a gas leak, refer to

z Remedy the cause of the gas leak. z Open the gas cock, place the electrical system of the

boiler into operation and fit the casing, see box 59, 54, 55 or 51.

box 46, 43 or 44.

1) is correctly fitted.

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44 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

Page 45

Actions 7

box 85 Check the non return valve

z Remove the fan, see box 76 to box 79. z Check to see if the non return valve (item 5 and 6, if fitted)

is soiled or defective.

z Loosen the upper nut (item 2). z Loosen the two lower nuts (item 1). z Turn the securing plate 180° counterclockwise (item 3). z Remove the fan part (item 7). z Bend the silicon seal (item 4). z Remove the plastic valvehousing (item 5). z Check the silicon valve (item 6) and replace when

necessary.

z After checking, refit all components in reverse order.

Make sure that the cam (item A) of the silicon valve is mounted in the correct manner (A).

z First tighten the upper nut (item 2), then tighten the lower

two nuts (item

1).

z Refit all other components in reverse order, then put the

boiler into service, see box 51, 54 or 55.

box 86 Check the Venturi

box 87

z Check the article number of the Venturi against those

listed in the table in

z Check to ensure that the correct Venturi has been fitted.

This is done by comparing the article numbers listed against the number on the Venturi (item 1), see box 5.

z Check the Venturi for soiling.

box 88

z Refit the Venturi and fan by following the above procedure

in reverse order.

z Refit the air silencer tube. z Refit the casing and place the boiler into operation,

see box 51, 53, 54 or 55.

box 89 Check the pump – mechanical restrictions

z Remove casing, see box 47. z Remove the vent screw on the front of the pump,

see box 57.

ACAUTION!

Note that water will squirt out when the vent screw is removed. Have a bucket and a supply of dry cloths to hand.

box 5.

z Take the boiler out of operation, see box 43, 44 or 47. z Remove the air intake duct, see box 77. z Remove the Venturi, see box 81, item 1.

box 90

z Put the electrical system of the boiler into operation,

see box 54 and 55.

z Check to see if the pump is running. The pump may

become mechanically blocked if the heating system has been out of use for an extended period.

z Insert a screwdriver and attempt to make the pump turn.

Use the screwdriver to turn the fan wheel in the direction of rotation shown on the identification plate of the pump.

z Refit the vent screw to the pump. z Fit casing, see box 51.

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Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 45

Page 46

Actions7

box 91 Check the pump – activation

HDANGER OF FATAL ACCIDENT

due to electric shock

ACAUTION!

To prevent damage, do not insert the measuring electrodes of the multimeter too far into the holes of the plug-and-socket connection.

ACAUTION!

Close gas valve during pump test.

z Take the boiler out of operation, see box 43, 44 or 47.

box 92

box 94

z Insert the power supply plug of the pump. z Fit casing, see box 51.

box 95 Check the pump – power supply cable

HDANGER OF FATAL ACCIDENT

due to electric shock

z Take the boiler out of serve and tip the DBA control panel

forwards, see box 43, 44, 47 or 63.

z Loosen the six screws and remove the rear section,

see box 70.

z Remove the power supply plug of the pump, see box 92.

box 96

JP1

z Pull out the power supply plug of the pump.

box 93

z Set the multimeter to “measure AC voltage”.

Minimum measuring range: 250V AC.

z Put the boiler into operation, see box 54 and 55. z Carry out a multimeter check to verify whether 230V AC is

present at both outer contacts (L and N) of the power supply plug of the pump during locking fault code

[2l] .

z Check the power supply cable of the pump for breaks.

The electrical resistance measured at each individual wire must be approximately 0

z Check the power supply cable of the pump for internal

short circuits. The level of electrical resistance, measured between two wires chosen at random, must be infinitely high.

z Fit the power supply plug of the pump, fit the DBA control

panel and place the boiler into operation, see or 55.

box 97 Check the pump – soiling

z Take the boiler out of operation and drain the heating

system, see box 43, 44, 47, 45, 49 or 50.

Ω.

box 53, 54

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46 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

Page 47

Actions 7

box 98

z Loosen the four Allen screws on the pump. z Remove the top section of the pump.

box 99

box 102

z Loosen the union nuts (item 1) at the top and side of the

pump.

z Remove the pump.

box 103

ACAUTION!

Fit new flat sealing rings when installing the new pump.

z Install the new pump. z Insert the power supply plug of the pump, fill and vent the

heating system of air and put the boiler into operation, see box 57 to 60.

z Fit casing, see box 51.

z Clean the pump impeller wheel.

box 100

z Refit the top section of the pump. z Fill and vent the heating system, see box 52 to 58. z Fit casing, see box 51.

box 101 Replace the pump

HDANGER OF FATAL ACCIDENT

due to electric shock

z Take the boiler out of operation and drain the heating

system, see box 43, 44, 47, 45, 49 or 50.

z Remove the power supply plug of the pump, see box 92.

box 104 Check the flow, safety and DHW temp. sensors

(applies to external cylinder only)

z Put the boiler into operation, see box 54 or 55. z Open the hot water tap and wait for the boiler to start up,

then gradually close the hot water tap to bring the CH flow temperature to over 80

z Take the boiler out of operation and remove the casing,

see box 43, 44 or 47.

°C.

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Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 47

Page 48

Actions7

box 105

z Pull out the plug of the safety sensor.

box 107

z Pull out the plug of the flow NTC sensor.

box 108

box 106

z Set multimeter to “measure resistance”. z Measure the resistance of the safety sensor.

z Set multimeter to “measure resistance”. z Measure the resistance of the flow NTC sensor.

box 109

z Measure the electrical resistance of the flow NTC sensor

and safety sensor.

z Measure the electrical resistance of the flow NTC sensor

and check the earth (ground) connection of the safety sensor. This must be infinitely high. The measured resistance of the flow NTC sensor is virtually identical to that of the safety sensor.

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48 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

Page 49

Actions 7

box 110

z Use a digital contact-type thermometer to measure the

temperature in the vicinity of the corresponding sensor.

z Compare the resistance readings with the values listed in

box 111.

z Replace the corresponding sensor if the reading fluctuates

by more than 10% with respect to the reference value (e.g. infinitely high resistance in the event of a line break or resistance of 0

Ω in the case of a short circuit).

z Reinsert the plug. z Refit the casing and place the boiler into operation,

see box 51, 53, 54 or 55.

box 111

Resistance readings (approximate values) for the sensor

Temperature

in °C

0 29,490

5 23, 462 55 3,271

10 18,787 60 2, 760

15 15,136 65 2, 339

20 12, 268 70 1, 990

Resistance in ΩTemperature

in °C

Resistance in

box 113

1) 2)

121110

JP3

25 10,000 75 1, 700

30 8,197 80 1,458

35 6,754 85 1,255

40 5,594 90 1,084

45 4, 656 95 940

50 3 ,893 100 817

box 112 Check the flow, safety and DHW temperature

sensors – cables

HDANGER OF FATAL ACCIDENT

due to electric shock

ACAUTION!

To prevent damage, do not insert the measuring electrodes of the multimeter too far into the holes of the plug-and-socket connection.

z Take the boiler out of service and tip the DBA control panel

forwards, see box 43, 44, 47 or 63.

z Loosen the six screws and remove the rear section,

see box 70.

z Pull out the plugs of the flow NTC sensor and safety

sensor, see

box 105.

Key to terms:

1) Flow NTC sensor

2) Safety sensor

z Set multimeter to “measure resistance”. z Check the cables of the flow NTC sensor and safety

sensor for breaks. The electrical resistance measured at each individual wire must be approximately 0

Ω.

z Check the cables of the flow NTC sensor and safety

sensor for internal short circuits. The level of electrical resistance, measured between two wires, must be infinitely high.

z Measure the electrical resistance of the flow NTC sensor

and check the earth (ground) connection of the safety sensor. This must be infinitely high.

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Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 49

Page 50

Actions7

box 114

Room Controller

Hot water tank sensor

24 VAC

3-way valve

Hot water tank sensor

1 2

3 4

5 6 7

Room Controller

24 VAC

3-way valve

z Set multimeter to “measure resistance”. z Detach the cables of the DHW temperature sensor (item 3

and 4) from the DBA control panel.

z Measure the resistance of the cable of the DHW

temperature sensor and check it for short circuits and breaks. See box 112.

z Fit the cables of the DHW temperature sensor to the DBA

control panel (item 3 and 4).

box 117

ACAUTION!

Note that water will squirt out when the sensor is removed. Have a bucket and a supply of dry cloths to hand.

z Pull out the plug of the safety sensor (item 1). z Detach the stop spring of the safety sensor by pulling in

the direction of the arrow (item 2).

z Remove the safety sensor (item 3).

box 118

box 115

z Insert the cables of the corresponding DHW temperature

or outside air-temperature sensor.

z Fit the DBA control panel and place the boiler into

operation, see

box 54, 55 or 51.

box 116 Replace the flow NTC sensor and/or safety

sensor

z Take the boiler out of operation, drain the heating system

and pull out the plug of the corresponding sensor, see box 43, 44, 47, 45, 47, 49 or 50.

ACAUTION!

Note that water will squirt out when the sensor is removed. Have a bucket and a supply of dry cloths to hand.

z Detach the stop spring of the flow NTC sensor by pulling

in the direction of the arrow.

z Remove the flow NTC sensor.

box 119

z Fit the corresponding new sensor. z Fill the heating system, vent it of air and place the boiler

into operation, see box 52 to 58.

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50 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

Page 51

Actions 7

box 120 Check the flue-gas STL

z Take the boiler out of operation, see box 43, 44 or 47.

box 121

z Remove both plugs of the flue-gas STL.

box 122

box 126 Check the flue-gas STL - cable

HDANGER OF FATAL ACCIDENT

due to electric shock

z Take the boiler out of service and tip the DBA control panel

forwards, see

z Loosen the six screws and remove the rear section,

see box 70.

z Remove both plugs of the flue-gas STL, see box 121.

box 127

box 43, 44, 47 or 63.

JP4

z Set multimeter to “measure resistance”. z Check the electrical resistance of the flue-gas STL.

box 123

z Check the temperature of the flue gas at the test point on

the flue pipe.

z Compare the flue-gas temperature reading with the

measured electrical resistance, see

box 124

Flue-gas STL

Temperature Status Resistance in Ω

box 124.

≤ 105 °C closed 0

>105 °C open infinitely high

box 125

z Insert both plugs at the flue-gas STL and fit the cover on

the test point of the flue pipe. Put the boiler into operation,

box 51, 54 or 55.

see

z Set multimeter to “measure resistance”. z Check the cables of the flue-gas STL for breaks. z The electrical resistance measured at each individual wire

must be approximately 0

z Check the cables of the flue-gas STL for internal short

circuits. The level of electrical resistance, measured between two wires chosen at random, must be infinitely high.

box 128

z Insert both plugs at the flue-gas STL, fit the DBA control

panel, attach the casing and place the boiler into operation, see

box 129 Replace the flue-gas STL

z Take the boiler out of operation, see box 43, 44 or 47. z Remove both plugs of the flue-gas STL, see box 121. z Twist the flue-gas STL anticlockwise to remove. z Fit the new flue-gas STL. Use a new seal when doing so. z Insert both plugs at the flue-gas STL and place the boiler

into operation, see box 51, 54 or 55.

box 51, 54 or 55.

Ω.

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Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 51

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Actions7

box 130 Check the glow ignitor – activation

HDANGER OF FATAL ACCIDENT

due to electric shock

z Take the boiler out of operation, see box 43, 44 or 47.

box 131

z Pull out the plug of the glow ignitor (item 1).

box 132

box 134 Check the glow ignitor – resistance

HDANGER OF FATAL ACCIDENT

due to electric shock

z Take the boiler out of operation, see box 43, 44 or 47. z Remove the plug of the glow ignitor, see box 131.

box 135

z Set multimeter to “measure resistance”. z Check to see if the electrical resistance of the glow ignitor

lies between 50 and 300 Ω.

z Set the multimeter to “measure AC voltage”.

Minimum measuring range: 230V AC.

z Put the boiler into partial-load or full-load operation,

see box 13.

z Check to see whether, with the operating code C [0c]

110 - 230 V AC is measured at the plug.

box 133

z Take the boiler out of operation, see box 43. z Connect the plug of the glow ignitor. z Put the boiler into operation, see box 54, 55 or 51.

box 136

z Connect the plug of the glow ignitor. z Fit the casing and place the boiler into operation,

see box 51, 54 or 55.

box 137 Check the glow ignitor – power supply cable

HDANGER OF FATAL ACCIDENT

due to electric shock

ACAUTION!

To prevent damage, do not insert the measuring electrodes of the multimeter too far into the holes of the plug-and-socket connection.

z Take the boiler out of serve and tip the DBA control panel

forwards, see

box 43, 44, 47 or 63.

z Loosen the six screws and remove the rear section,

see box 70.

z Remove the plug of the glow ignitor, see box 131.

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52 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

Page 53

Actions 7

box 138

JP1

z Set multimeter to “measure resistance”. z Check the mains cable of the glow ignitor for breaks.

The electrical resistance measured at each individual wire must be approximately 0

z Check the mains cable of the glow ignitor for internal short

circuits. The level of electrical resistance, measured between any two wires, must be infinitely high.

Ω.

box 142

ACAUTION!

The filament of the glow ignitor consists of sintered material and is highly breakable.

z Fit a new glow ignitor. z Connect the plug of the glow ignitor. z Put the boiler into operation, see box 51, 54 or 55.

box 143 Measure the ionisation current

z Take the boiler out of operation, see box 43, 44 or 47.

box 144

box 139

z Connect the plug of the glow ignitor. z Fit the DBA control panel and place the boiler into

operation, see box 51, 54 or 55.

box 140 Replace the glow ignitor

HDANGER OF FATAL ACCIDENT

due to electric shock

z Take the boiler out of operation, see box 43, 44 or 47. z Remove the plug of the glow ignitor, see box 131.

box 141

z Pull out the ionisation electrode plug (item 1).

box 145

z Use a multimeter that is specially designed to measure the

ionisation current.

z Loosen the fixing nut of the glow ignitor (item 1). z Remove the mounting plate (item 2). z Detach the glow ignitor (item 3).

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Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 53

Page 54

Actions7

box 146

z Set the multimeter to “measure direct current”.

Measuring range: Microamperes [µA].

z Connect the multimeter in series the ionisation circuit. z Put the boiler into service mode, see box 54, 55 or 13. z Check to see if the ionisation current, during service mode,

operating code C [lo] , > 5 µA (micro amperes) and, with operating code The value is 0 (zero), or between 1.3 and 50 µA.

box 147

z Take the boiler out of operation, see box 43 or 44. z Detach the multimeter. z Connect the plug of the ionisation electrode. z Turn the operating switch on the boiler to position “0”,

see box 55.

z Put the boiler into operation, see box 51, 54 or 55.

C [hi] , > 25 µA.

box 150

z Connect the plug of the ionisation electrode. z Put the boiler into operation, see box 51, 54 or 55.

box 151 Check the ionisation electrode – cable

HDANGER OF FATAL ACCIDENT

due to electric shock

z Take the boiler out of service and tip the DBA control panel

forwards, see box 43, 44, 47 or 63.

z Loosen the six screws and remove the rear section,

see box 70.

z Remove the plug of the ionisation electrode, see box 144.

box 152

JP4

box 148 Check the ionisation electrode – short circuits

z Take the boiler out of operation, see box 43, 44 or 47. z Loosen the plug-in connection of the ionisation electrode,

see box 144.

box 149

z Set multimeter to “measure resistance”. z Take a reading at the electrode to check whether there is

a possible short circuit between the ionisation electrode and earth (ground). The electrical resistance between the ionisation electrode and earth (ground) must be infinitely high.

z Set the multimeter to “measure resistance”. z Take a reading at the ionisation electrode to check

whether there is a possible break in the cable of the electrode. The electrical resistance of the cable must be approximately 0

box 153

z Take an earth (ground) reading check whether there is a

possible short circuit between the cable of the ionisation electrode and earth (ground). The electrical resistance between the ionisation electrode cable and earth (ground) must be infinitely high.

Ω.

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54 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

Page 55

Actions 7

box 154

z Connect the plug of the ionisation electrode. z Refit the DBA control panel, by following the above

procedure in reverse order, and place the boiler into operation, see box 51, 54 or 55.

box 155 Check and replace the ionisation electrode

z Take the boiler out of operation, see box 43, 44 or 47. z Remove the plug of the ionisation electrode, see box 144.

box 156

box 158

z Check the ionisation electrode for signs of wear (item 2),

damage (item 3) or soiling (item 4).

box 159

z Replace the ionisation electrode if required. z Fit the ionisation electrode. z Connect the plug of the ionisation electrode. z Put the boiler into operation, see box 51, 54 or 55.

z Loosen the fixing nut on the ionisation electrode (item 1). z Remove the mounting plate (item 2). z Detach the ionisation electrode (item 3).

box 157

z Set multimeter to “measure resistance”. z Take a reading at the ionisation electrode to check

whether there is a possible break in the electrode cable. The electrical resistance of the ionisation electrode cable must be approximately 0

Ω.

box 160 Check the ionisation circuit – earth (ground)

lead

z Check to ensure that the earth (ground) lead of the

ionisation circuit (item

1) has been correctly fitted.

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Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 55

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Actions7

box 161 Check the gas valve – power supply plug

z Take the boiler out of operation, see box 43, 44 or 47.

box 162

z Check to ensure that the power supply plug (item 1) has

been inserted correctly into the gas valve.

box 163

z Put the boiler into operation, see box 51, 54 or 55.

box 164 Check the gas valve – activation

box 168

z Remove the plug from the gas valve (item 1).

box 169

JP4

z Take the boiler out of operation, see box 43, 44 or 47.

box 165

z Run the boiler at full load, see box 54, 55 and

box 13, step 14.

z Set the multimeter to “measure DC voltage”.

Minimum measuring range: 40V DC.

z Check to see if the gas valve has been activated. During

operating code must be detectable at both the centre and upper contacts (item 1 and 2).

box 166

z Put the boiler into operation, see box 51, 54 or 55.

box 167 Check gas valve – electrical resistance of

power supply cable

z Take the boiler out of operation and remove the DBA

control panel, see box 43, 44, 47, 63 or 70.

C [0l], or somewhat later, 20 – 24V DC

z Set multimeter to “measure resistance”. z Check the power supply cable of the gas valve for breaks.

The electrical resistance measured at each individual wire must be approximately 0 Ω.

z Check the power supply cable of the gas valve for internal

short circuits. The level of electrical resistance, measured between two wires, must be infinitely high.

box 170

z Insert the gas valve plug. z Fit the DBA control panel and place the boiler into

operation, see

box 171 Check the gas valve – internal electrical

z Take the boiler out of operation, see box 43, 44 or 47. z Remove the power supply plug of the gas valve,

see box 168.

box 51, 54 or 55.

resistance

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56 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

Page 57

Actions 7

box 172

±70 - 110 Ω ±180 - 250 Ω

z Set multimeter to “measure resistance”. z Take a reading at the coils to check the internal electrical

resistance of the two gas valve coils. The electrical resistance between the middle and lower contact must be approx. 70 – 110 between the middle and upper contact must be approx. 180 – 250 Ω (item 2).

box 173

z Fit the power supply plug to the gas valve. z Put the boiler into operation, see box 51, 54 or 55.

box 174 Replace the gas valve

ADANGER OF FATAL ACCIDENT!

All work on gas pipework and gas-fitting components must be carried out by a company registered and authorised for this purpose.

z Take the boiler out of operation and close the gas tap,

see box 43, 44, 46 or 47.

z Remove the fan, see box 77, 78, 79 or 80.

Ω (item 1). The electrical resistance

box 176

z Fit the gas injector to the new gas valve. z Fit the new gas valve to the fan. z Fit the fan to the boiler, insert the air silencer tube into the

fan, fit the gas supply pipe to the gas valve and insert the plugs into the fan and gas valve.

z Fit the air silencer tube to the fan.

ACAUTION!

When attaching the gas supply pipe to the gas valve, ensure that the flat rubber seal is fitted correctly between the gas supply pipe and gas valve.

z Fit the gas supply pipe to the gas valve. z Insert the power supply plug into the gas valve, then insert

the power supply plug and tacho cable plug into the fan.

z Open the gas cock and place the boiler into full-load

operation, see box 59, 54, 55 or 13.

z Carry out a gas-leak check. Check the tightness of all

components that were loosened during removal of the gas valve. Use an authorised foam-type leak detection product for this purpose.

z Remedy the cause of the gas leak. z Put the boiler into operation, see box 51, 54 or 55.

box 177 Check the ON/OFF or modulating control

function

z Take the boiler out of service and tip the DBA control panel

forwards, see

box 43, 44, 47 or 63.

z Loosen the six screws and remove the rear section,

see box 70.

box 178

box 175

z Pull the gas injector (item 1) out of the gas valve.

Room Controller

Hot water tank sensor

24 VAC

3-way valve

Hot water tank sensor

1 2

3 4 5 6 7

Room Controller

24 VAC

3-way valve

z Bridge the two contacts, terminal 1 and 2.

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Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 57

Page 58

Actions7

box 179

z Put the boiler into full-load operation, see box 54, 55 or 61.

If the boiler goes into heating mode within approx. 3 minutes :-h. , the cause of the fault lies outside the boiler.

z Take the boiler out of operation, see box 43 or 44. z Remove the bridge connection. z Connect the ON/OFF or modulating control element to the

boiler.

z Put the boiler into operation, see box 51, 54 or 55.

box 180 Adjust the output flow rate (applies to

combination boilers only)

box 182

ADANGER OF DAMAGE TO THE SYSTEM!

Before removing the servomotor, check to see if the 3-way valve is in its "heating mode" position, and wait for the boiler display code C [0h] to appear. This prevents sudden pressure surges occurring in the heating circuit while the removal operation is taking place, and the resultant accidental opening of the pressure relief valve.

z Remove the stop spring (item 1). z Remove the servomotor.

ACAUTION!

As the water pressure and pipework resistance in the plumbing system can vary widely with each situation, it is important to adjust correctly the DHW flow rate at the boiler. Take a DHW flow rate reading, see

box 12.

Adjust the DHW flow rate at the flow regulator for hot water. To check the DHW flow rate press and hold the down "D" arrow and read off the display in ltrs/m. – To increase the DHW flow rate:

turn the flow regulator in direction “+”.

– To reduce the DHW flow rate:

turn the flow regulator in direction “–”.

z Adjust the flow rate of hot water at one of taps where the

user is likely to require hot water at an ideal temperature. Factory default setting: see factory settings in the installation instruction. This assumes a cold water input temperature of 10 °C.

box 181 Check the internal 3-way valve – movement of

the servomotor

z Take the boiler out of operation, see box 43, 44 or 47.

box 183

z Put the boiler into operation, see box 54 and 55. z Use the "Settings" menu on the boiler DBA control panel

to adjust the temperature to 60

°C, see box 14 or 18.

z Open a hot water tap. z Check to see if the servomotor of the internal 3-way valve,

during operating code

C [0c], rotates through a full

revolution.

z Close the hot water tap. z Check to see if the servomotor runs back again.

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58 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

Page 59

Actions 7

box 184

z Fit the servomotor to the 3-way valve. z Insert the stop spring. z Adjust the DBA control panel, see box 61. z Fit casing, see box 51.

box 185 Check the internal 3-way valve – activation

ACAUTION!

To prevent damage, do not insert the measuring electrodes of the multimeter too far into the holes of the plug-and-socket connection.

z Take the boiler out of operation, see box 43, 44 or 47.

box 186

z Pull out the power supply plug of the servomotor.

box 187

z Put the boiler into operation, see box 54 and 55.

box 188

box 189

z Insert the power supply plug of the 3-way valve. z Put the boiler into operation, see box 51 or 61.

box 190 Internal 3-way valve – replace the servomotor

z Take the boiler out of operation, see box 43, 44 or 47. z Remove the power supply plug of the servomotor,

see box 186.

z Remove the servomotor, see box 182. z Fit the new servomotor by following the above procedure

in reverse order.

z Put the boiler into operation, see box 51, 54 or 55.

box 191 Check the internal 3-way valve – power supply

cable

HDANGER OF FATAL ACCIDENT

due to electric shock

ACAUTION!

To prevent damage, do not insert the measuring electrodes of the multimeter too far into the holes of the plug-and-socket connection.

z Take the boiler out of operation and remove the DBA

control panel, see

box 43, 44, 47, 63 or 70.

z Remove the power supply plug of the servomotor of the

3-way valve, see box 186.

box 192

1 ~

3 0

z Set the multimeter to “measure AC voltage”.

Minimum measuring range: 40V AC.

z Use the "Settings" menu on the boiler DBA control panel

to adjust the temperature to 60

°C, see box 14 or 18.

z Open a hot water tap. z Check to see if, during operating code C [0c] at plug-in

contacts “1” and “3”, 24

V AC is detected between plug-in

contacts “1” and “2” .

z Close the hot water tap. z Check to see if, during operating code C [0h], 24 V AC

is detected at plug-in contacts “1” and “2” .

JP4

z Set multimeter to “measure resistance”. z Check the power supply cable of the 3-way valve for

breaks. The electrical resistance measured at each individual wire must be approximately 0 Ω.

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Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 59

Page 60

Actions7

box 193

z Check the power supply cable of the 3-way valve for

internal short circuits. The level of electrical resistance, measured between two wires chosen at random, must be infinitely high.

box 194

z Insert the power supply plug of the 3-way valve, fit the

DBA control panel and place the boiler into operation, see box 51, 54 or 55.

box 198 Replace the internal 3-way valve – drive

mechanism

z Take the boiler out of operation and drain the heating

system, see

z Remove the servomotor of the 3-way valve, see box 182.

box 199

box 48 to 51.

z Remove the stop spring (item 1) by pulling it in the

direction of the arrow.

box 200

box 195 Check the internal 3-way valve – drive

mechanism

z Take the boiler out of operation, see box 43, 44 or 47. z Remove the servomotor of the 3-way valve, see box 182.

box 196

z Check to ensure that the drive mechanism of the 3-way

valve is running smoothly. This is done by gradually pushing the spring fully home by hand and allowing the spring to return gradually to its home position.

z Remove the drive mechanism (item 1) of the 3-way valve.

ACAUTION!

Note that water will squirt out when the drive mechanism is removed. Have a bucket and a supply of dry cloths to hand.

box 197

z Refit the servomotor, following the above procedure in

reverse order.

z Put the boiler into operation, see box 51, 54 or 55.

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60 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

Page 61

Actions 7

box 201

z Fit the new drive mechanism on the internal 3-way valve.

Ensure that the flat side faces upwards.

box 205

z Remove the stop spring and 3-way valve-motor.

box 206

123

box 202

z Connect the servomotor of the 3-way valve by following

the above procedure in reverse order.

z Fill the heating system, vent it of air and place the boiler

into operation, see box 52 to 58.

box 203 Replace the internal 3-way valve

z Take the boiler out of operation and drain the heating

system, see box 48 to 51.

box 204

z Pull the plug (item 1) out of the pump. z Loosen the four screws (item 3) on the pump. z Remove the return pipe with spring (item 4). z Remove the pipe to the expansion vessel with spring

(item 5).

z Pull out the pump (item 2).

z Disconnect the cable from the main switch, see box 54. z Pull the spring off the flow NTC sensor lead (item 1). z Pull out the flow NTC sensor plug (item 2). z Pull the main switch cable out of the nut (item 3).

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Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 61

Page 62

Actions7

box 207

3 3 H3 3

122 12

z Remove all pipes beneath the boiler.

ACAUTION!

Note that water will squirt out when the internal 3-way valve is removed. Have a bucket and a supply of dry cloths to hand.

z Loosen the gas pipe at the gas valve. z Remove the two screws (item 1). z Remove the complete hydraulic assembly. z Remove the four M8 nuts (item 2). z Remove the five screws (item 3). z Remove the plastic block (H3).

box 209

z Replace the housing of the 3-way valve.

box 210

z Refit all components, following the above procedure in

reverse order.

z Fill the heating system, vent it of air and place the boiler

into operation, see box 52 to 58.

box 211 Check the Buderus 24V AC external

3-way valve – movement of the servomotor

box 208

z Loosen the screw in the plastic block (item 2). z Remove the pressure relief valve (item 1), see box 276

or 277.

z Remove the drive mechanism on the internal 3-way valve,

see box 200.

ACAUTION!

Note that water will squirt out when the internal 3-way valve is removed. Have a bucket and a supply of dry cloths to hand.

z Put the boiler into operation, see box 54 and 55. z Adjust the hot water in the "Settings" menu on the DBA

control panel of the boiler to 60

z Open a hot water tap. z Check to see if the servomotor of the Buderus

24V AC external 3-way valve, during the operating code C [0c] rotates from the setting for heating mode (position “ (position “2”).

z Close the hot water tap. z Check to see if the servomotor runs back again. z Adjust the hot water in the “Settings” menu on the DBA

control panel of the boiler, see

1”) to the position for hot water mode

°C, see box 61.

box 61.

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62 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

Page 63

Actions 7

box 212 Check the Buderus 24V AC external

3-way valve – activation (1)

ACAUTION!

To prevent damage, do not insert the measuring electrodes of the multimeter too far into the holes of the plug-and-socket connection.

z Take the boiler out of operation, see box 43, 44 or 47.

box 213

z Remove the power supply plug of the servomotor of the

Buderus 24V AC external 3-way valve.

box 214

z Put the boiler into operation, see box 51, 54 or 55.

box 215

Plug-in contacts of Buderus 24V

AC external 3-

way valve

2 24V AC 5 3 0V AC 6 6 _ \ __ 7

Purpose Plug-in contacts

on DBA control

panel

box 216

z Insert the power supply plug of the Buderus

24V AC external 3-way valve.

z Put the boiler into operation, see box 51, 54 or 55.

box 217 Replace the Buderus 24V AC external 3-way

valve – servomotor

z Take the boiler out of operation, see box 43, 44 or 47. z Remove the power supply plug of the servomotor of the

Buderus 24V AC external 3-way valve, see

box 218

z Remove the servomotor of the Buderus 24V AC external

3-way valve. To release the servomotor press the release catch (item 1) and twist the servomotor.

ADANGER OF DAMAGE TO THE SYSTEM!

Before removing the servomotor, check to see if the Buderus 24V AC external 3-way valve is in its "heating mode" position, and wait for the boiler display code [0h] to appear. This prevents sudden pressure surges occurring in the heating circuit while the removal operation is taking place, and the resultant accidental opening of the pressure relief valve.

box 219

z Fit the new servomotor by following the above procedure

in reverse order.

z Put the boiler into operation, see box 51, 54 or 55.

box 213.

z Set the multimeter to “measure AC voltage”.

Minimum measuring range: 40V AC.

z Open a hot water tap. z Adjust the hot water in the "Settings" menu on the DBA

control panel of the boiler to 60 °C, see box 61.

z Check to see if, during operating code C [0c], 24 V AC

is detected at plug-in contacts “2” and “6”.

z Close the hot water tap. z Check to see if, during operating code C [0h] , 24 V AC

is detected at plug-in contacts “2” and “3”.

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Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 63

Page 64

Actions7

box 220 Check the Buderus 24V AC external

3-way valve – power supply cable

ACAUTION!

To prevent damage, do not insert the measuring electrodes of the multimeter too far into the holes of the plug-and-socket connection.

z Take the boiler out of operation, see box 43 or 44. z Remove the power supply plug of the servomotor of the

Buderus 24V AC external 3-way valve, see box 213.

z Remove the connection of the power supply cable of the

Buderus 24V AC external 3-way valve at the boiler.

z Set multimeter to “measure resistance”. z Check the power supply cable of the Buderus

24V AC external 3-way valve for breaks. The electrical resistance measured at each individual wire must be approximately 0

Ω.

z Check the power supply cable of the Buderus

24V AC external 3-way valve for internal short circuits. The level of electrical resistance, measured between two wires chosen at random, must be infinitely high.

z Insert the power supply plug of the Buderus

24V AC external 3-way valve.

z Connect the power supply cable of the Buderus 24V AC

external 3-way valve at the boiler.

z Put the boiler into operation, see box 54 or 55.

box 221 Check the Buderus 24V AC external

3-way valve – drive mechanism

z Take the boiler out of operation, see box 43 or 44. z Remove the servomotor of the Buderus 24V AC external

3-way valve, see

box 218.

box 222

box 224 Replace the Buderus 24V AC external 3-way

valve – drive mechanism

z Take the boiler out of operation and drain the heating

system, see

box 48 to 51.

z Remove the servomotor of the Buderus 24V AC external

3-way valve, see box 213 or 218.

box 225

z Remove the drive mechanism of the Buderus

24V AC external 3-way valve using the wrench supplied with the drive mechanism.

ACAUTION!

Note that water will squirt out when the drive mechanism is removed. Have a bucket and a supply of dry cloths to hand.

box 226

z Fit the new drive mechanism to the Buderus

24V AC external 3-way valve.

z Connect the servomotor of the Buderus 24V AC external

3-way valve by following the above procedure in reverse order.

z Fill the heating system, vent it of air and place the boiler

into operation, see box 52 to 58.

box 227 Check the Buderus 24V AC external

3-way valve – installation

z Check to ensure that the drive mechanism of the Buderus

24V AC external 3-way valve is running smoothly. This is done by gradually pushing the spring fully home by hand and allowing the spring to return gradually to its home position.

box 223

z Refit the servomotor, following the above procedure in

reverse order.

z Put the boiler into operation, see box 54 or 55.

z Use the letters marked on the 3-way valve to check

whether the Buderus 24V AC external 3-way valve is correctly fitted:

A = flow of storage-type water heater B = CH flow AB= boiler flow

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64 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

Page 65

Actions 7

box 228 Check the Buderus 24V AC external

3-way valve – activation (2)

Room Controller

Hot water tank sensor

24 VAC

3-way valve

Plug-in contacts

on DBA control

panel

1 2 3

5 6 7

Room Controller

Hot water tank sensor

24 VAC

3-way valve

Purpose Plug-in contacts

of Buderus 24V

AC external 3-

way valve 5 24V AC 2 6 0V AC 3 7_ \ __ 6

box 230 Measure the gas input pressure – static and

dynamic

ADANGER OF FATAL ACCIDENT!

All work on gas supply pipes and gas-fitting components must be carried out by a company registered and authorised for this purpose.

z Take the boiler out of operation and close the gas tap,

see box 43, 44, 46 or 47.

z Open some of the radiator valves.

box 231

z Take the boiler out of operation and remove the DBA

control panel, see box 43, 44, 47, 63 or 70.

z Put the boiler into operation, see box 54 and 55. z Open hot water tap. z Adjust the hot water in the "Settings" menu on the DBA

control panel of the boiler to 60 °C, see

box 61 and box 14.

z Set the multimeter to “measure AC voltage”.

Minimum measuring range: 40V AC.

Plug-and-socket connection DBA control panel conn.

67 36 25

z Check whether, with operating code C [0c] active,

there is a voltage of 24 V AC at the plug-in contacts item 6 and item 7.

z Close the hot water tap. z Check whether, with operating code C [0h] active,

there is a voltage of 24 V AC at the plug-in contacts item 5 and item

box 229

z Fit the DBA control panel and place the boiler into

operation, see

box 51, 54 or 55.

ACAUTION!

The pressure gauge should be accurate to 2 decimal places (X.00).

z Reset the digital pressure gauge to zero.

ACAUTION!

Throughout the measuring operation, keep the pressure gauge in the same position (horizontal or vertical) in which it was reset to zero.

z Loosen by two turns the screw on the gas connection

pressure measuring nipple (item

1).

z Fit the pressure gauge to the gas connection pressure

measurement nipple (item

2).

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Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 65

Page 66

Actions7

box 232

z Open the gas tap, see box 59. z Put all other gas-fired devices (e.g. gas ovens and stoves,

etc.) out of use.

z Check to see if static gas input pressure does not rise

slowly for 2

minutes.

z Run all other gas-fired appliances (e.g. gas ovens and

stoves, etc.) at full capacity, but do not operate the boiler.

z The static gas input pressure must be:

for natural gas minimum 20 mbar and for propane minimum 37 mbar.

z Open the gas cock and place the boiler into service mode,

see box 59, 54, 55 or 13.

z Press the service button “A" twice. z Capacity during service mode is at "C" [hi] = 100 %

(max. heating capacity).

z Wait for 1 minute, until the boiler starts at full load. z Measure the working gas pressure at the appliance. z Measure the difference between the static and working

gas input pressure. The working pressure may be: for natural gas minimum 17 mbar and for propane minimum 30 mbar.

z Take the boiler out of operation and close the gas tap, see

box 43, 44 or 46.

z Remove the pressure gauge. z Tighten the screw on the gas connection pressure

measurement nipple.

z Open the gas tap, see box 59. z Use a detection product to check the gas connection

pressure measurement nipple for leaks. Use an authorised foam-type leak detection product for this purpose.

z Fit the casing and place the boiler into operation,

see box 51, 54 or 55.

box 233 Measure and adjust the gas/air ratio

ADANGER OF FATAL ACCIDENT!

All work on gas pipework and gas-fitting components must be carried out by a company registered and authorised for this purpose.

z Take the boiler out of operation and close the gas tap,

see box 43, 44, 46 or 47.

z Open some of the radiator valves.

box 234

z Reset the digital pressure gauge to zero.

ACAUTION!

Throughout the measuring operation, keep the pressure gauge in the same position (horizontal or vertical) in which it was reset to zero.

z Loosen by two turns the screw on the burner pressure

measurement nipple (item 1).

z Connect the pressure gauge to the burner pressure

measurement nipple (item 2).

box 235

z Open the gas cock and place the boiler into service mode,

box 59, 54, 55 or 13.

see

z Press the service button “A" once. z Capacity during service mode is at C [lo] = 25%

(max. heating circuit capacity).

z Wait a short time for the boiler to be adjusted downwards.

box 236

ABB

–15 –10 –5 0 5 (Pa)

–0,15 –0,10 –0,05 0,00 0,05 (mbar)

Key to terms: A = correct; B = false; C = turn anticlockwise; D = turn clockwise

z Check the gas/air ratio during service mode operation.

The differential pressure (p must be –5 Pa (±5 Pa) (as indicated by the measuring device: –10 to 0

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66 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

– p

gas

air

)

Pa).

Page 67

Actions 7

box 237

z Use the adjustment screw to readjust the gas/air ratio if

necessary (item 1).

INOTE:

The adjustment screw (4mm Allen screw) is located behind the screw-on cover.

box 238

z Take the boiler out of operation and close the gas tap,

see box 43, 44 or 46.

z Remove the pressure gauge. z Tighten the screw on the burner pressure measurement

nipple.

z Open the gas cock and place the boiler into full-load

operation, see box 59, 54, 55 and 13.

z Wait for the boiler to start. z Use a detection product to check the burner pressure

measurement nipple for leaks. Use an authorised foamtype leak detection product for this purpose.

z Take the boiler out of operation, see box 43 or 44. z Fit the casing and place the boiler into operation,

see box 51, 54 or 55.

box 239 Vent the gas flow pipe.

box 240

z Loosen by two turns the screw on the gas connection

pressure measuring nipple (item

z Connect a long hose (item 2) to the gas connection

pressure measurement nipple and then run this hose out of the building.

box 241

z Leave the gas cock open until no further air escapes from

the hose, see box 59.

z Close the gas cock, see box 46. z Remove the hose from the gas connection pressure

measurement nipple.

z Tighten the screw on the gas connection pressure

measurement nipple.

z Open the gas tap, see box 59. z Use a detection product to check the gas connection

pressure measurement nipple for leaks. Use an authorised foam-type leak detection product for this purpose.

z Fit the casing and place the boiler into operation,

see box 51, 54 or 55.

box 242 Replace the automatic air vent

z Take the boiler out of operation and drain the heating

system, see

box 48 to 50.

1).

ADANGER OF FATAL ACCIDENT!

All work on gas supply pipes and gas-fitting components must be carried out by a company registered and authorised for this purpose.

z Take the boiler out of operation and close the gas tap,

see box 43, 44, 46 or 47.

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Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 67

Page 68

Actions7

box 243

z Twist the automatic air vent in the direction of the arrow to

remove.

box 244

z Fit the new automatic air vent by following the above

procedure in reverse order.

z Fill the heating system, vent it of air and place the boiler

into operation, see

box 245 Replace the burner

box 52 to 58.

box 247

z Turn the gas/air unit clockwise by about 10°.

box 248

HDANGER OF FATAL ACCIDENT

due to electric shock

ADANGER OF FATAL ACCIDENT!

All work on gas supply pipes and gas-fitting components must be carried out by a company registered and authorised for this purpose.

z Take the boiler out of operation and close the gas tap,

see box 43, 44, 46 or 47.

z Remove the power supply plug of the glow ignitor,

see box 131.

z Remove the plug of the ionisation electrode, see box 144. z Remove the power supply plug of the gas valve, union nut

and air silencer tube, see

box 246

box 77.

z Remove the gas/air unit along with the burner.

box 249

z Pull out both fan plugs (item 1).

z Loosen both screws (item 1). z Remove the burner.

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68 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

Page 69

Actions 7

box 250

z Fit the new burner to the gas/air unit. Note that a new seal

must be fitted between the burner and gas/air unit.

box 251

z Remove the heat exchanger-gas/air seal.

box 252

z Check the heat exchanger-gas/air seal for signs of ageing. z Replace the heat exchanger-gas/air seal if required. z Refit all components, following the above procedure in

reverse order.

z Open the gas cock and place the boiler into full-load

operation, see box 59, 54, 55 and 13.

z Carry out a gas-leak check. Check the tightness of all

components that were loosened in the course of removal of the burner. Use an authorised foam-type leak detection product for this purpose.

z Remedy the cause of the gas leak. z Open the gas cock and place the boiler into operation,

see box 59, 54, 55 or 51.

box 255

z Install the new sight glass. Use a new seal when doing so. z Put the boiler into operation, see box 51, 54 or 55.

box 256 Replace/clean condensate trap and syphon

z Take the boiler out of operation, see box 43, 44 or 47.

box 257

z Remove the condensate trap (item 1) and syphon

(item 2).

box 253 Replace the sight glass

z Take the boiler out of operation, see box 43, 44 or 47.

box 254

box 258

z Clean the condensate trap and syphon. z Fit the new or cleaned syphon. z Put the boiler into operation, see box 51, 54 or 55.

z Loosen both screws (item 1). z Remove the sight glass along with the seals.

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Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 69

Page 70

Actions7

box 259 Replace/clean the heat exchanger

HDANGER OF FATAL ACCIDENT

due to electric shock

ADANGER OF FATAL ACCIDENT!

All work on gas supply pipes and gas-fitting components must be carried out by a company registered and authorised for this purpose.

z Take the boiler out of operation, close the gas cock and

drain the heating system, see box 46 or 48 to 50.

z Remove the power supply plug of the glow ignitor,

see box 131.

z Remove the plug of the ionisation electrode, see box 144. z Remove the power supply plug of the gas valve, union nut

and air silencer tube, see

z Pull out both fan plugs, see box 78, item 1. z Remove the gas/air unit along with the burner,

see box 247 and 248.

z Remove the heat exchanger-gas/air seal, see box 251.

box 260

box 77.

box 261

z Remove the restrictor baffle (item 1).

box 262

1

z Open the four clip fastenings(item 1). z Clean the heat exchanger with a brush and compressed

air or with TAB2. In the event of serious restriction, continue with box 261.

1

z Remove the stop spring on the top left-hand side of the

heat exchanger by turning it towards the arrow.

box 263

z Remove the stop spring on the bottom right-hand side of

the heat exchanger by turning it towards the arrow.

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70 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

Page 71

Actions 7

box 264

z Pull the heat exchanger towards the arrow to remove.

box 265

box 266

z Clean the heat exchanger with compressed air, a high-

pressure hose or with water and a soft brush.

ACAUTION!

When cleaning the heat exchanger never use a steel brush.

ACAUTION!

When using compressed air: Use eye protection, inhalation protection and hearing

protection.

box 267

z Check the seal on the heat exchanger casing (item 1) for

signs of ageing and replace if required.

z Replace the four O-rings (item 2), two on each side.

ACAUTION!

Observe the position of the heat exchanger during fitting. Insert the upper section of the heat exchanger at the top.

z Fit the new or cleaned heat exchanger and all other

components by following the above procedure in reverse.

ACAUTION!

The released coil (item 1) touches the underside.

ACAUTION!

Insert a new heat exchanger-gas/air seal before fitting the gas/air unit.

We reserve the right to make technical modifications Buderus Ltd. • http://www.buderus-domestic.co.uk

Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 71

Page 72

Actions7

box 268

z Fill the heating system, vent it of air, open the gas tap and

place the boiler into operation, see

box 269 Replace plate heat exchanger

z Take the boiler out of operation, see box 43, 44 or 47. z Close the cold water tap. z Drain the heating system, see box 48 to 51. z Open hot water tap.

box 270

box 59 or 52 to 58.

box 272

z Remove condensate trap.

box 271

z Remove both screws from the plate heat exchanger.

box 273

z Remove the plate heat exchanger.

z Remove syphon.

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72 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

Page 73

Actions 7

box 274

z Fit new plate heat exchanger. z Renew the four O-rings if necessary. z Refit the plate heat exchanger and secure with the two

screws.

z Open the cold water service valve. z Open the hot water tap in order to clean the new plate heat

exchanger (inside).

z Close the hot water tap. z Fill the heating system, see box 52. z Fit the casing and place the boiler into operation,

see box 51, 54 or 55.

box 275 Replace the pressure relief valve

z Take the boiler out of operation and drain the heating

system, see

box 276

box 48 to 50.

box 278

z Fit the new pressure relief valve and all other components

by following the above procedure in reverse.

z Fill the heating system, vent it of air and place the boiler

into operation, see box 52 to 58.

box 279 Replace the turbine flowmeter

z Remove the stop spring (item 2) of the pressure relief

valve.

z Remove the pressure relief valve (item 1) in the direction

of the arrow.

box 277

z Remove the stop spring.

box 280

z Use a screwdriver to lever out the turbine flowmeter.

box 281 Replace the DBA control panel

z Release the pressure relief valve from the section of

condendsate outlet pipework by pulling in the direction of the arrow.

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Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 73

HDANGER OF FATAL ACCIDENT

due to electric shock

z Take the boiler out of operation and remove the DBA

control panel, see

box 43, 44, 47, 63 or 70.

Page 74

Actions7

box 282

JP1 JP2 JP4 JP3

z Disconnect the five plugs (harness - item 1, JP1, JP2, JP4

and JP3) from the DBA control panel.

box 283

box 284 Check the EEPROM (KIM)

z Check the plug-and-socket connection on the EEPROM

(KIM).

box 285 Check the junction box – 230V room-

temperature connection

z Remove the DBA control panel. z Fit the new DBA control panel, following the above

procedure in reverse order.

ACAUTION!

Please ensure that the new DBA control panel is fitted with the correct KIM (see box 284). The coloured stripe on the new KIM should match that of the old KIM. Otherwise, refit the old KIM to the new DBA control panel.

z Fit the casing and place the boiler into operation,

see box 51, 54 or 55.

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74 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

z Remove the casing lock and lower the DBA. z Remove the cover from the RTH converter/Junction box

(item 1).

z Run the 230V power supply cable through the cable

pipework.

z Connect the 230V cable to item 1. The switch live should

be connected to terminal 1 and the Neutral to terminal 2 of the 230V connection (item 2).

Page 75

box 286 Check the junction box – 0 Volt room-

temperature connection

z Remove the casing lock and lower the DBA, see box 285. z Remove the cover from the RTH converter/junction box,

see box 285, item 1.

z Run the volt free power supply cable through the cable

pipework.

z Connect the volt free cable at position 1 and 2 of the volt

free connection, see box 285, item 3.

Actions 7

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Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 75

Page 76

Appendix8

8 Appendix

box 287 Wiring diagram

Buderus controller, RTH converter or ON/OFF-controller

pin 1

pin 17

pin 1

Low voltage

pin 17

pin 4

JP2 JP4 JP3JP1

pin 1

pin 6

pin1

High voltage

hot-water tank sensor

24 VAC

earth

3-way valve

DBA

1 2

3 4 5 6 7

Mains

230 VAC,

50 Hz

24 VAC

0 VAC

switch contact

DBA

1) only for Buderus 500-24/S: remove the link at the connection of the hot water tank sensor

2) only for Buderus 500-24/C and 500-28/C

safety sensor

JP3

11 1

ionisation electrode

flow sensor

flue gas thermostat

241

JP4

231

LPEN

Turbine

Buderus

gas valve

fan

sensor

hot-water

3-way valve

24V AC external

LPEN

231

glow ignitor

pump

JP1 JP2 JP4 JP3

Mains

JP2

120 VAC

230 VAC, 50 Hz

JP1

Mains switch

We reserve the right to make technical modifications Buderus Ltd. • http://www.buderus-domestic.co.uk

76 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

Page 77

9 Index

box 288 Index

Index

Adjust the output flow rate (applies to combination

boilers only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .box 180

Check and replace the ionisation electrode . . . . . . . . . . . . . . .box 155

Check fan – activation 230V AC . . . . . . . . . . . . . . . . . . . . . . . . .box 66

Check fan – power supply cable (230 V AC) . . . . . . . . . . . . . . .box 69

Check fan – tacho cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .box 73

Check fan and/or replace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .box 76

Check gas valve – electrical resistance of power

supply cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .box 167

Check the Buderus 24V AC external 3-way

valve – activation (1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .box 212

Check the Buderus 24V AC external 3-way

valve – activation (2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .box 228

Check the Buderus 24V AC external 3-way

valve – drive mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . .box 221

Check the Buderus 24V AC external 3-way

valve – installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .box 227

Check the Buderus 24V AC external 3-way

valve – movement of the servomotor . . . . . . . . . . . . . . . . .box 211

Check the Buderus 24V AC external 3-way

valve – power supply cable . . . . . . . . . . . . . . . . . . . . . . . . .box 220

Check the by-pass valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .box 14

Check the flow, safety and DHW temperature sensors –

cables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .box 112

Check the flow, safety and DHW temperature sensors

(applies to external cylinder only) . . . . . . . . . . . . . . . . . . . .box 104

Check the flue-gas STL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .box 120

Check the flue-gas STL – cable . . . . . . . . . . . . . . . . . . . . . . . . .box 126

Check the gas valve – activation . . . . . . . . . . . . . . . . . . . . . . . .box 164

Check the gas valve – internal electrical resistance . . . . . . . .box 171

Check the gas valve – power supply plug . . . . . . . . . . . . . . . . .box 161

Check the glow ignitor – activation . . . . . . . . . . . . . . . . . . . . . .box 130

Check the glow ignitor – power supply cable . . . . . . . . . . . . . .box 137

Check the glow ignitor – resistance . . . . . . . . . . . . . . . . . . . . . .box 134

Check the internal 3-way valve – activation . . . . . . . . . . . . . . .box 185

Check the internal 3-way valve – drive mechanism . . . . . . . . . box 195

Check the internal 3-way valve – movement of the servomotor box 181

Check the internal 3-way valve – power supply cable . . . . . . .box 191

Check the ionisation circuit – earth (ground) lead . . . . . . . . . .box 160

Check the ionisation electrode – cable . . . . . . . . . . . . . . . . . . .box 151

Check the ionisation electrode – short circuits . . . . . . . . . . . . .box 148

Check the pressure control valve . . . . . . . . . . . . . . . . . . . . . . . . .box 85

Check the pump – activation . . . . . . . . . . . . . . . . . . . . . . . . . . . .box 91

Check the pump – mechanical restrictions . . . . . . . . . . . . . . . . .box 89

Check the pump – power supply cable . . . . . . . . . . . . . . . . . . . .box 95

Check the pump – soiling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .box 97

Check/replace fuses (1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .box 62

Removal of casing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .box 47

Replace plate heat exchanger . . . . . . . . . . . . . . . . . . . . . . . . . .box 269

Replace the automatic air vent . . . . . . . . . . . . . . . . . . . . . . . . . .box 242

Replace the Buderus 24V AC external 3-way

valve – drive mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . .box 224

Replace the Buderus 24V AC external 3-way

valve – servomotor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .box 217

Replace the burner . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .box 245

Replace the DBA control panel . . . . . . . . . . . . . . . . . . . . . . . . .box 281

Replace the flow NTC sensor and/or safety sensor . . . . . . . . .box 116

Replace the flue-gas STL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .box 129

Replace the gas valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .box 174

Replace the glow ignitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .box 140

Replace the internal 3-way valve . . . . . . . . . . . . . . . . . . . . . . . .box 203

Replace the internal 3-way valve – drive mechanism . . . . . . .box 198

Replace the pressure relief valve . . . . . . . . . . . . . . . . . . . . . . . .box 275

Replace the pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .box 101

Replace the sight glass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .box 253

Replace/clean condensate trap and syphon . . . . . . . . . . . . . . .box 256

Replace/clean the heat exchanger . . . . . . . . . . . . . . . . . . . . . .box 259

Shutting down . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .box 43

Technical specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .box 5

Vent the gas flow pipe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .box 239

Wiring diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .box 287

Draining the system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .box 48

Filling the system and venting it of air . . . . . . . . . . . . . . . . . . . . .box 52

Initial startup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .box 59

Internal 3-way valve – replace the servomotor . . . . . . . . . . . . .box 190

Measure and adjust the gas/air ratio . . . . . . . . . . . . . . . . . . . . .box 233

Measure the gas input pressure – static and dynamic . . . . . .box 230

Measure the ionisation current . . . . . . . . . . . . . . . . . . . . . . . . . .box 143

We reserve the right to make technical modifications Buderus Ltd. • http://www.buderus-domestic.co.uk

Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 77

Page 78

Notes

We reserve the right to make technical modifications Buderus Ltd. • http://www.buderus-domestic.co.uk

78 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006

Page 79

Notes

We reserve the right to make technical modifications Buderus Ltd. • http://www.buderus-domestic.co.uk

Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006 79

Page 80

Heating system specialist:

Buderus

Cotswold Way

Warndon Worcester WR4 9SW

Telephone: 01905 - 752 936

Fax: 01905 - 753 130

Customer Services:

Technical Product Support:

Sales:

Returns:

Spares:

Tel: 0870 - 421 5933 Tel: 0870 - 421 5944 Tel: 01905 - 752 640 Tel: 01905 - 752 531 Tel: 01905 - 752 576

Fax: 01905 - 456 445 / 455 394 Fax: 01905 - 455 392 Fax: 01905 - 754 620

www.buderus-domestic.co.uk

721.489A – 4612 – 02/2006

Buderus 500 - 28/C, 500 - 24/C, 500 - 24/S Servicing Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

1 General

2 Servicing manual user guide

3 Operation

4 Function

5Symptoms

6 Diagnosis

7Actions

8 Appendix

9 Index