MHS Boilers 318, 378, 508, 559, 624 Maintance Manual

Ultramax Floor Standing Condensing Boiler

Operating & Maintenance Manual

For Models 318 - 1018

MHS Boilers Ltd

3 Juniper West

Fenton Way

Basildon Essex

SS15 6SJ

01268 546700 Telephone [phone] Fax

WWW.MHSBOILERS.COM

L263

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Contents

Ultramax Technical data
Ultramax Dimensions
1 Introduction

1.1 General

1.2 Supplier

1.3 This document

1.4 Service

1.5 General restrictions

2 Description

2.1 General

2.2 Main components

2.2.1 Description of principal components

2.3 Boiler control

2.4 Safety aspects

3 Safety
4 Delivery and transport

4.1 Delivery

4 .2 Packaging

4.3 Transport

5 Installation

5.1 Regulations

5.2 Boiler room

5.2.1 General

5.2.2 Set up

5.2.3 Ventilation

5.3 Connections

5.3.1 Gas connection

5.3.2 Electrical connection

5.3.3 Water connections

5.3.4 Combustion air supply

5.3.4.1 General

5.3.4.2 Air supply pipe

5.3.5 The flue system

5.3.5.1 General

5.3.5.2 Chimney

5.3.6 Condensate discharge

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5.4 Hydraulic system

5.4.1 General

5.4.2 Water flow

5.4.2.1 Flow rate and resistance

5.4.2.2 Pump characteristics

5.4.2.3 Isolating valves

5.4.2.4 Valves

5.4.2.5 Water flow protection

5.4.3 Water pressure

5.4.3.1 Operating pressure

5.4.3.2 Boiler expansion tank

5.4.3.3 System expansion tank

5.4.3.4 Water pressure protection

5.4.4 Water temperature

5.4.5 Water quality

5.4.6 Examples of hydraulic systems

6 Operating instructions

6.1 Function

6.2 Regulation

6.3 Control module

6.4 Fault indications

6.5 Start-up

6.6 Shut-down

6 .7 Warnings

7 Commissioning

7.1 General

7 .2 Commissioning

8 Maintenance

8.1 Safety

8.2 General

8.3 Procedure

8.4 Cleaning the burner and heat exchangers

8.5 Cleaning the filter/screen in the gas combination block

8.6 Ionisation measurement

8.7 Replacing the frequency Inverter

8.8 Service

9 Conversion formulae and factors

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Ultramax Technical data

Type

318 378 443 508 559 624

730 826 923 1018

Nominal heat output
Nominal heat input (nett.)
Minimum heat output

kW
kW
kW

315
333

83

374
396
100

438
464
112

502
532
133

553
585
146

613
653
187

717
764
218

811
865
247

906
966
276

1000
1066

305

Pilot Burner kW 30 30 30 30 30

Gas consumption
Nat Gas H

(10,9kWh/m3)

Propane (12,8 kWh/kg)

m3/h
kg/h

30.5

26.0

36.3

30.9

42.6

36.2

48.8

41.5

53.7

45.7

59.9

51.0

70.1

59.7

79.4

67.6

88.6

75.5

97.8

83.3

Gas inlet pressure
Nat Gas(min.)
Nat Gas(max.)
Propane (min./max.)

mbar
mbar
mbar

18

100

30/50

18

100

30/50

18

100

30/50

18

100

30/50

18

100

30/50

18
25

100

18
25

100

18
25

100

18
25

100

18
25

100

Water capacity
Max. working pressure

dm3

bar

38 6 41 6 44 6 47 6 50 6 53

6

70

6

75

6

80

6

85

6

Gas connection

G1
G2

G

R11⁄2" - -

Rp1

1⁄2

-

Rp2" - Rp2"

-

Rp2"

Rp2"

Rp2"

Rp2"

DN65

PN6

DN65

PN6

Water connections

W

DN65

PN6

DN65

PN6

DN65

PN6

DN65

PN6

DN65

PN6

DN65

PN6

DN80

PN6

DN80

PN6

DN80

PN6

DN80

PN6

Flue connection D mm 250 250 300 300 300 300 350 350 400 400

Safety valve
Boiler connection
Relief connection
Standard setting

bar

1"

1

1⁄4"

3

1"

11⁄4"

3

11⁄4"
11⁄2"

3

11⁄4"
11⁄2"

3

11⁄4"
11⁄2"

3

11⁄4"

11⁄2"

3

11⁄4"
11⁄2"

3

11⁄2"

2"

3

11⁄2"

2"

3

11⁄2"

2"

3

Power supply
Frequency
Fuse

V

Hz

A

400

50
10

400

50
10

400

50
10

400

50
10

400

50
10

400

50
16

400

50
16

400

50
20

400

50
20

400

50
20

Max. electrical power
consumption unit pump
maximum total

kW
kW
kW

0.42

0.46

0.88

0.67

0.72

1.39

0.71

0.72

1.43

0.71

0.72

1.43

0.73

1.15

1.88

0.90

1.15

2.05

0.90

1.15

2.05

1.27

1.15

2.42

1.27

1.50

2.77

1.27

1.50

2.77

Boiler weight, empty, ±5% kg 525 560 615 645 675 740 840 950 1070 1200

Dimensions height H
width B
length incl. connections L

mm
mm
mm

1355

830

1918

1355

930

1908

1355
1130
1908

1355
1130
1908

1355
1230
1958

1355
1330
2265

1355
1130
2653

1355
1130
2653

1355
1330
2658

1355
1330
2658

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Ultramax 318 – 559 Dimensions

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Ultramax 318 – 559 Dimensions

Type 318 376 443 508 559

B* mm 830 930 1130 1130 1230

B1 mm 710 810 960 1010 1110

B2 mm 120 120 170 120 120

B3 mm 646 746 946 946 1046

D mm 250 250 300 300 300

G1

R 11⁄2" - - - -

G2

- Rp 11⁄2" Rp 2" Rp 2" Rp 2"

H1 mm 1115 1205 1205 1205 1120

L mm 1918 1908 1908 1908 1958

L1 mm 555 545 545 545 595

L2 mm 1362 1362 1362 1362 1362

L3 mm 231 231 231 231 231

L4 mm 108 108 108 108 108

W

DN65 PN6 DN65 PN6 DN65 PN6 DN65 PN6 DN65 PN6

B = Dimensions with external casing (panels) in place

* = To obtain the dimensions without the external casing, subtract 64 mm from dimension eBi.

(Changes may be introduced without notice)

As a result of manufacturing tolerances, there may be small variations in the dimensions.

Conditions applicable to above table:

- Nominal capacity measured at: 60 - 80°C.

- Gas consumption at: 1013 mbar, 15°C, dry

- Gas categ o ry: 2

2H3P

- Gas pressure: The unit is adjusted during manufacture for a

gas supply pressure of 25 mbar.

- Appliance categ o ry: B 23, C53, C33 or C63

- Protection deg r ee: I P20

Types R318 to 559 are suitable for nominal distribution pressures of both 20 and 100 mbar for natural

gas. For higher gas pressures, a separate gas pressure regulator must be

installed in consultation with the local gas supplier. The dynamic supply pressure must never fall

below 18 mbar (see para. 5.3.1).

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Ultramax 624 – 1018 Dimensions

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Ultramax 624 – 1018 Dimensions

Type 624 730 826 923 1018

B mm 1330 1130 1130 1330 1330

B1 mm 1210 1003 1053 1203 1253

B2 mm 665 565 565 665 665

B3 mm 120 127 77 127 77

B4 mm 1146 946 946 1146 1146

B5 mm 65 115 65 115 65

D mm 300 350 350 400 400

G

Rp2" Rp2" Rp2" DN65 PN6 DN65 PN6

H mm 1355 1355 1355 1355 1355

H1 mm 1125 1400 1400 1155 1155

L mm 2265 2653 2653 2658 2658

L1 mm 595 610 610 615 615

L2 mm 700 1166 1166 1166 1166

L3 mm 108 88 88 88 88

W

DN65 PN6 DN80 PN6 DN80 PN6 DN80 PN6 DN80 PN6

(Changes may be introduced without notice)

As a result of manufacturing tolerances, there may be small variations in the dimensions.

Conditions applicable to the above table:

- Nominal capacity measured at: 60 - 80°C.

- Gas consumption at: 1013 mbar, 15°C, dry

- Gas category: 2

2H3P

- Appliance category: B23, C53, C33 of C63

- Protection degree: IP20

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1 Introduction

1.1 General

Through their unique construction, the Ultramax range of central heating units are renowned for their:

- high thermal efficiency

- environmental friendliness

- light weight and small dimensions

- durability

- low noise production

- large regulating range

- available with many different options.

Active and market required research enables MHS Boilers Ltd to offer solutions for the most

provocative heating demands.

1.2 Supplier

MHS Boilers Ltd are proud to supply and technically support the Ultramax Range of boilers throughout

the United Kingdom.

For advice or more information please contact your local sales representative or our head office via

01268 591010.

1.3 This document

This documentation has been written to aid the following target groups:

- the consulting engineer

- the heating installer

- the service engineer

- the user.

Because these target groups require mostly similar information and also specific information, our

technical documentation has been integrated to provide these target groups with the necessary

general and specific information to install, service and operate this product.

If additional information is required please contact your local representative or our head office via

01268 591010.

The following aspects will be explained:

- general description

- technical specifications

- necessary services for system design and unit installation

- example systems

- maintenance instructions.

Operating instructions for the user can be found on the unit. See also chapter 6.

1.4 Service

For commissioning and assistance in maintenance matters, please contact the Technical Services

Department via 01268 591010.

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1.5 General restrictions

The application, installation and maintenance of MHS products must always be carried out

in accordance with the requirements (legal or otherwise), specifications and standards applicable

to such installations.

All data, information and suggestions provided by MHS Boilers Ltd. in relation to its products are

based on careful investigation. Nevertheless, neither MHS Boilers Ltd. nor any other organisation

connected with MHS Boilers Ltd. accepts any liability for application, installation or exploitation

that occurs outside its sphere of influence.

Changes may be incorporated without prior notice. MHS Boilers Ltd. accepts no obligation to
adapt previously delivered products to incorporate such changes.

2 Description

2.1 General

The Ultramax series are environmentally friendly modulating gas fired heating boilers that can vary its

output from 25% to 100% of its maximum capacity.

The Ultramax series consists of 10 models in a range from 318 to 1018 kW.

The units have an extremely low emission of NO

x and CO, so that this boiler satisfies the most

stringent European requirements.

The R2700/R2800/R2900 series have CE approval for all relevant European countries.

The series are registered under the product identification numbers 0063AQ6600. (318 - 559) &

0063AR3514. (624 - 1018)

The boilers can be supplied either as a standard (category B23) or a room sealed (categories C53,

C33 or C63) appliance.

Working principle and construction

Air is blown into the appliance, as required, by a speed-controlled fan and thoroughly mixed with

gas in the correct proportions.

A temperature controller compares the desired water temperature with the temperature of the water

flow and sends a signal to the frequency converter to maintain the correct heating capacity.

The gas/air mixture so formed is passed through a cooled premix burner and ignited. The premix

burner is constructed of finned bimetallic pipes (internally from stainless steel and externally

from aluminium) with cast iron water headers.

Heat transfer takes place in two or three heat exchangers. The first heat exchanger is constructed

from smooth stainless steel pipes, while the second heat exchanger is fitted with laser welded,

stainless steel finned pipes. Both heat exchangers are fitted with cast iron profiled water distribution

components (headers) which guarantee an optimum water flow through the appliance.

The burner and the heat exchangers are connected in series.

The boiler pump ensures the correct water flow quantity.

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The Ultramax units have a small water capacity so that it can rapidly adjust to changing

conditions. It can be installed without any restrictions to the return water temperature. The

necessary water flow rate is ensured by the standard pump delivered with the appliance.

Application possibilities

Because of its construction, the Ultramax unit is suitable for use in heating systems:

- With a constant supply temperature

- With a weather dependent heating demand

- With low temperature condenser systems

- With optimised condensation

- With control by means of building optimizer/compensator system (0 – 10 Vdc = +2°C – +90°C),

see 5.3.2 connection terminals).

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2.2 Ultramax 318-559 Main components

1 Return connection 19 Flue gas collection chamber

2 Flue gas discharge attenuator 20 Combustion chamber

3 Water flow switch 21 Electrical cable duct

4 Safety valve 22 Condensate discharge

5 Inlet connection 23 Inspection opening

6 Filling / drainage valve 24 Gas valve unit

7 Cover 25 Fan

8 Distribution plate 26 Connection box

9 Burner 27 Control panel

10 First heat exchanger 28 Casing

11 Gas filter 29 Air inlet damper

12 Second heat exchanger 30 Butterfly valve

13 Gas train 31 Mixing chamber

14 Frame 32 Boiler pump

15 Water circulation piping A Air

16 Flue gas discharge B Gas

17 Third heat exchanger

(Special Order Appliances Only) C Flue gas

18 Condensate collection tank D Condensate

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2.2 Ultramax 623-1018 Main components

1 Return connection 18 Condensate collection tank

2 Flue gas discharge attenuator 19 Flue gas collection chamber

20 Combustion chamber

3 Water flow switch 21 Electrical cable duct

4 Safety valve 22 Condensate discharge

5 Flow connection 23 Gas valve unit

6 Filling/drainage valve 24 Fan

7 Cover 25 Connection box

8 Distribution plate 26 Control panel

9 Burner 27 Casing

10 First heat exchanger 28 Air inlet damper

11 Gas filter 29 Main mixing chamber

12 Second heat exchanger 30 Pilot gas valve

13 Gas train 31 Pilot mixing chamber

14 Frame 32 Boiler pump

15 Water circulation piping A Air

16 Flue gas discharge B Gas

17 Third heat exchanger

(Special Order Appliances Only) C Flue gas

D Condensate

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2.2.1 Description of principal components

The boiler is constructed from the following principal components:

Fan

This consists of a fan casing, a fan impeller and an electric motor. The fan sucks in combustion air

and increases the air pressure.

Air inlet damper

A specially developed air inlet damper ensures a low noise level. As an option, this can be provided

with an air filter or with an air inlet opening so that the appliance can function as a room sealed

appliance.

Gas train

The principal component of the gas train is the main gas valve/proportional pressure regulator. The

quantity of gas is adjusted in proportion to the quantity of air being supplied. The quantity

of air depends on the speed of the fan. The unit is fitted with a gas filter as standard.

Mixing chamber

This area is used for the thorough mixing of the gas and the combustion air.

Burner

After the gas/air mixture has been distributed over the burner with the aid of a distribution plate, the

mixture is burned on the surface of the burner in such a way that the flame is directed

downward. The burner is air and water cooled. The water distribution components are made from

cast iron and have a profile that ensures that an optimum distribution and flow are obtained.

Heat exchangers

The primary heat exchanger is constructed from smooth stainless steel tubes. These transfer

most of the heat energy to the system water. The secondary heat exchanger, which consists

of laser welded stainless steel finned tubes, transfers the remaining heat from the flue gasses to

the system water. All the water distribution components are constructed from cast iron and have

a profile that ensures that optimum distribution and flow are obtained. The space between the

burner and the secondary heat exchanger forms the combustion chamber.

Special order appliances only have a third heat exchanger is attached which consists of one or more

stainless steel fin tube(s), switched in series, in form of a spiral. It is arranged on the back of the boiler

on the flue gas collection chamber.

The boiler pump ensures the water flow quantity.

The third heat exchanger is switched parallel to the boiler and has a flow of 5 - 10% of the entire water

flow.

Water circulation pipes

These pipes connect the burner to the heat exchangers.

Water connections

These consist of a flow connection and a return connection. Both of these connections are

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provided with a filling/drain valve. The flow connection is also provided with a safety valve,

a flow switch and a temperature sensor.

Boiler pump

The boiler pump is mounted on the return connection to the unit and is directly connected electrically

to the appropriate terminals in the connection box. The capacity and the working head of the

pump is sufficient to overcome both the resistance of the boiler and some system resistance.

Flue gas collection chamber

The stainless steel flue gas collection chamber is mounted under the heat exchanger. This chamber

is provided with a flue gas exhaust connection, a condensate drain connection and an

inspection opening.

Frame

The frame is constructed from steel profile sections. Vibration absorption dampers are supplied

separately and must be fitted after the unit has been placed in position.

The casing

The casing consists of panels that can be removed easily without the aid of tools.

The electrical section

This includes the control and safety circuits for the unit.

Connection box

The electrical power supply for the boiler, the terminals, the pump connections and the pump

relay are mounted in an easily accessible connection box. The supply cables can easily be fed to

the connection box via the cable duct inside the boiler.

2.3 Boiler control

The principle employed for the Boiler Management Unit is as follows:

The boiler begins operating on receipt of a heating demand. This heating demand is generated either:

A. If the measured supply temperature is lower than the desired temperature.

B. As a result of a manual operation mode having been selected,

C. In standby mode, when the water temperature falls below the frost protection temperature.

After the boiler has started up, the PID controller sends a signal to the frequency converter. This

converter controls the speed of the fan. Depending on the quantity of air moved by the fan, the

proportional pressure regulator ensures that the corresponding quantity of gas is added.

In this way the boiler capacity is continually adjusted and the boiler can accurately follow the

heating demand. If the boiler is operating at minimum capacity and the temperature of the supply

water rises above the desired value, the boiler will be shut down. As soon as the temperature of

the supply water falls below the set value, the boiler will be re-started.

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2.4 Safety aspects

The boiler contains the following safety components:

- Flame protection with 1x re-start (ionisation)

- Water flow protection

- Maximum water temperature protection

- Gas valve test

- Gas valve leak test (option)

- Minimum air pressure protection

- Boiler pump motor over-heating protection (Clixon).

If one of these components operates, this results in a lockout fault. Lockout faults can only be

cancelled by resetting the unit.

The unit is fitted with a safety valve that opens at 3 bar.

3 Safety

Installation instructions

Read through these instructions carefully before starting the installation.

The appliance must be installed by a recognised installer in accordance with the applicable national

and local regulations.

The installation may only be used for heating systems up to a maximum water temperature of

90°C.

It is expressly stated that these installation instructions must be seen as a supplement to the

above mentioned standards and regulations and that these standards and regulations must take

precedence over any information included in this technical manual.

Maintenance

Work on the electrical installation may only be carried out by an authorised installer in accordance

with the applicable electrical regulations.

Work on the gas and hydraulic installations may only be undertaken by properly trained personnel

in accordance with the safety regulations for gas installations.

Keep unauthorised persons away from the installation. Do not place any objects on the unit.

Remain out of the area of the hot water connection and the chimney to avoid burns.

Before starting any maintenance or service activities, disconnect the electrical power supply and

close the gas supply valve.

After completing any maintenance or service activity, check the whole installation.

As a supplement to the information provided in this technical manual, all applicable safety regulations

must be consulted to avoid accidents.

All panels forming part of the casing must be mounted. Panels may only be removed for maintenance

or service purposes. After performing maintenance or service activities, ensure that all

panels are replaced.

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Safety provisions

The installation may never be switched on if any of the panels have been removed or if any of the

safety devices have been disabled.

Instruction and warning stickers

None of the instruction and warning stickers attached to the installation may be removed or covered

and during the whole of the lifetime of the installation they must remain legible.

Replace any damaged or unreadable instruction and warning stickers immediately.

Modification

Modifications to the installation may only be carried out with the written approval of the manufacturer.

Danger of explosion

When activities are being undertaken in the boiler room, always follow the applicable instructions

“Working in an area where there is a danger of explosion”.

Installation

The appliance must be installed by an authorised installer in accordance with the applicable national

and local specifications and regulations. Carefully follow all the safety instructions.

Operation

In the event of a gas leak, switch off the unit and close the gas supply valve. Open doors and windows

and warn the appropriate authorities.

When the installation is re-commissioned, always follow the instructions for use.

Technical specifications

The specifications listed in this technical manual cannot be ignored.

4 Delivery and transport

4.1 Delivery

The appliances are completely assembled, tested and covered in a “heat-shrink” protective covering.

After delivery and removal of the protective covering, check the appliance for damage.

Check that the equipment delivered is in accordance with the order and the delivery note.

On delivery, check the data plate for the correct boiler type and gas supply pressure.

4.2 Packaging

For transport purposes, the unit is mounted on wooden blocks, fitted with protective bumpers

and covered in a “heat-shrink” protective covering.

4.3 Transport

For transport, consult the technical details for dimensions and weight.

Remove the covering preferably after transportation and positioning in the boiler room or remove

the panels before transporting the appliance. This is to prevent damage to the casing panels.

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Moving the appliance

A pallet truck or fork lift truck with a minimum fork length of 1 m can be used at the side of the

unit.

Rollers

After the wooden blocks have been removed, it is possible to move the appliance by rolling it over

tubes.

Lifting

The figure below shows how a unit can be safely lifted. To avoid damage to the panels, these

should first be removed. The wooden bars between the straps ensure that the unit will not be

damaged during lifting.

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Caution:

- Ensure that the lifting straps are of the correct quality!

- Never move the units over the heads of persons!

Dismantling and reassembly

When the unit cannot be placed in position because of its dimensions or weight, the boiler may be

partially dismantled.

When it is necessary to perform extensive dismantling, we advise you to make early contact with

your supplier. The unit can be delivered in parts, each of which has been pre-tested. We strongly

advise you to have dismantling and reassembly activities carried out by the MHS Technical Service

Department trained staff.

Dimensions and weights of Burner and Heat exchangers

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Burner

Type Length mm Breadth mm Height mm Weight kg

318 1010 760 400 105

376 1010 860 410 115

443 1010 960 410 120

508 1010 1050 420 130

559 1010 1150 420 135

624 1010 1310 500 140

730 1420 1010 500 210

826 1420 1110 500 215

923 1420 1210 500 220

1018 1420 1310 500 225

Heat Exchanger One

Type Length mm Breadth mm Height mm Weight kg

318 1030 760 150 90

376 1030 860 150 95

443 1030 960 150 110

508 1030 1050 150 115

559 1030 1150 150 120

624 1010 1310 160 135

730 1420 1010 160 180

826 1420 1110 160 185

923 1420 1210 160 190

1018 1420 1310 160 195

Heat Exchanger Two

Type Length mm Breadth mm Height mm Weight kg

318 1030 760 150 100

376 1030 860 150 110

443 1030 960 150 120

508 1030 1050 150 130

559 1030 1150 150 135

624 1010 1310 160 150

730 1420 1010 160 200

826 1420 1110 160 200

923 1420 1210 160 210

1018 1420 1310 160 210

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Dimensions and weights of the Condensate Collectors.

Condensate Collector

Type Length mm Breadth mm Height mm Weight kg

318 1320 590 800 25

376 1320 690 800 25

443 1320 790 800 25

508 1320 890 800 25

559 1320 990 800 25

624 1450 1070 400 35

730 1950 770 400 35

826 1950 870 400 35

923 1950 970 400 35

1018 1950 1070 400 35

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Dimensions and weights of the Frame.

Frame

Type Length mm Breadth mm Height mm Weight kg

318 1325 765 460 45

376 1325 865 460 45

443 1325 1065 460 50

508 1325 1065 460 50

559 1325 1165 460 50

624 1630 1266 500 60

730 2004 1066 500 70

826 2004 1066 500 70

923 2004 1266 500 70

1018 2004 1266 500 70

Positioning

Once the unit is in the correct position, the wooden blocks must be removed. The vibration absorption

dampers with spacers delivered with the unit must now be mounted as described in the instructions

delivered with them (see drawing). Thereafter, the water, gas, chimney, condensate and electrical

connections can be completed.

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Protection against frost

If the unit is out of use during the winter months there is a danger of freezing. Drain the water

from the installation using the filling/drainage valves.

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5 Installation

5.1 Regulations

The appliance must be installed by a recognised installer in accordance with the applicable national

and local specifications and regulations.

Commissioning should be carried out by the Technical Service Department of MHS Boilers Ltd, who

can also determine the composition and quality of the system water.

5.2 Boiler room

5.2.1 General

- The construction of the unit ensures that losses through radiation can be neglected

- Because of the low noise level, additional sound insulation of the boiler room is unnecessary

- Because of the position of the electrical components, a plinth is not required

- The unit is so constructed that the space required for it is small

- The range of applications for the boiler is that much greater because of the possibility to install

it as a room sealed appliance (see Section 5.3.4)

5.2.2 Set up

In order to avoid any difficulties, the following rules apply to the boiler room:

a Install the appliance in a frost-proof room

b Pay particular attention to the positioning of the appliance to ensure protection from freezing

and/or high temperatures. (Consult BS 6644)

c Ensure that the boiler room is sufficiently large, so that there is sufficient space on all sides of

the unit to permit maintenance and possible replacement of components to be carried out.

The recommended minimum free space is:

- 450 mm at one side

- 800 mm at the other side

- 450 mm at the rear

- 1000 mm at the front (space for free movement).

If you do not observe the recommended space requirements, future maintenance might be more

Difficult or impossible.

Hydraulic System Pressure Monitoring

All hydraulic systems connected to the Ultramax range of boilers must incorporate a system water low
pressure switch, in accordance with BS6644.

5.3 Connections

5.3.1 Gas connection

The gas connection must be made by a recognised installer in accordance with the applicable

national and local standards and regulations.

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The gas connection is made at the rear of the boiler.

The pressure of the gas supplied to the unit must be reduced to 20 mbar for natural gas or 37 mbar for

propane with the use of a gas pressure regulator if required.

The maximum gas pressure sustainable at the gas valve inlet connection is 100 mbar for models 318 -

559 and 25 mbar for models 624 - 1018

The loss of pressure in the connecting pipes must be such that, at maximum boiler capacity, the

pressure must never fall below 20 mbar for natural gas or 37 mbar for propane.

5.3.2 Electrical connection

The electrical connections and provisions must comply with the applicable national and local

standards and regulations.

The units are wired in accordance with the electrical diagram supplied with the appliance.

The electrical connections, the terminals and the boiler pump relay are mounted in a separate

connection box behind the front panel.

This front panel can be simply removed by pulling the lower edge of the panel forward.

Behind this panel are two cover plates which can be removed by unscrewing the M5 bolts.

The terminal strip with the connection clamps are mounted behind the lower cover plate.

The cables to be connected (power supply, control) enter the appliance via the rear of the unit,

and pass via the cable duct at the inner right hand side to the connection box at the front of the

unit.

The connection box is provided with cable glands and connection terminals.

The boiler pump is provided with thermal protection and a pump relay.

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The appliance can be switched on and off with the switch on the control panel.

The power supply voltage cannot be removed from the boiler pump relay in this way.

The installer must fit a mains isolator switch in the power supply to the unit within the boiler

room. This can be used to switch off the power to the unit for maintenance purposes or in the

event of a problem.

In accordance with the applicable standards and regulations, an emergency shut-off must be

fitted at the exits from the boiler room. In the event of a calamity, the power supply to the unit can be

switched off.

Earth leakage trips can give problems when they are used in combination with frequency converters.

In some countries this is actually forbidden.

There are two reasons for this:

a All rectifiers (not only frequency converters) can cause direct currents to flow in the mains

power supply and which can reduce the sensitivity of the safety switch

b The asymmetric loading caused by radio interference filters can result in the premature operation

of the earth leakage trip, which in turn will result in the unit being switched off.

In order to prevent malfunctions occurring as a result of inductive or high frequency signals,
or static electricity, screened cables must be employed for all low voltage and control signals
between the boiler and externally connected units. The screening must be earthed at both ends
of the cable.

Electro-technical data

Type

Fan control

and safety

components

Pump

Total electrical

consumption

(max)

Supply

1 Phase

Power

Consumption

(max)

Supply **

3 Phase

Power

consumption

*** max)

V kW V kW kW

318

240 0.42 400 0.46 0.88

376

240 0.67 400 0.72 1.39

443

240 0.71 400 0.72 1.43

508

240 0.71 400 0.72 1.43

559

240 0.73 400 1.15 1.88

624

240 0.90 400 1.15 2.15

730

240 0.90 400 1.15 2.15

826

240 1.27 400 1.15 2.45

923

240 1.27 400 1.50 3.12

1018

240 1.27 400 1.50 3.12

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Electro-technical data

* Tolerance on voltage: 230 V +10% /-15% tolerance on frequency: 50 Hz } 5%

** tolerance on voltage: 400 V +10% /-15%

*** the stated pump power is based on the maximum power consumption in pump speed 3. The pump curves can be used to determine the

optimum operating point in relation to pump efficiency and power consumption.

Control and options

The appliances are fitted with a proportional regulation system. This can be made temperature

dependent with the aid of a 0 – 10 VDC (= +2°C – +90°C) signal. Also a domestic hot water priority

circuit belongs to the standard equipment.

In addition, the boiler regulating system can be extended by fitting one of the three options described

below:

BME option

This is a weather-compensated regulator with the following possibilities:

- Three on/off periods per day with three different temperatures

- Night-time temperature reduction

- 2 week programs

- Domestic hot water priority with time programming

- Anti-legionella provision

- Optimum start

- Room-temperature sensor (can be switched off)

- Two-wire communication bus connection

- Multi-language display

- External control.

E6 option

This is a regulator with which two secondary groups can be weather-dependently controlled. In

addition, domestic hot water temperature can also be regulated. All the settings can be adjusted

independently for each group. This E6 regulator can be further extended with an optimizing controller

for each group (BM). The boiler will then be directly weather-dependently controlled.

KKM option

This is a boiler cascade manager permitting up to eight boilers to be switched in cascade. The

KKM also has the same possibilities as the E6 option.

Connection terminals

Terminal Description

L1-L2-L3-N-E Boiler power supply; must be fused at 10 A, 16 A or 20 A dependant upon type of unit.

8 - 9 Domestic hot water primary pump control. This out put provides a voltage

(240 V) when the boiler is operational as a result of a domestic hot water heating

demand.

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10 - 11 Boiler enable (240 V). When these terminals are connected the primary pump will

be started and the boiler will be enabled. When there is an open circuit between

them the boiler will be shut down. The pump will also stop after the set run on

time. These terminals can be used, among other things, for set ting the boilers

to standby during the summer months whilst continuing to provide domestic hot

water priority.

12 - 13 Operating signal (240 V, 50 Hz, 1 A, N.O.). The operating signal falls off if a fault

has occurred more than 2 times within 6 minutes (the fault code will appear in

the display with a “3”) or if a fault is longer than 6 minutes active.

14 - 15 Control voltage for an external gas valve. This output begins to provide 240 V

before the boiler starts up; the voltage ceases after the boiler shuts down. This

output can be used to open hydraulic valves or to operate boiler room ventilation.

16 - 17 Calorifier thermostat (240 V). When these terminals are interconnected the boiler

will try to provide the set flow temperature programmed for the boiler. This input

only functions if terminals 34 - 35 are interconnected. The calorifier temperature

can also be regulated by a sensor (terminals 35-36).

18 - 19 Interlock input (240 V). If the connection between these terminals is interrupted

the boiler will be deactivated and wait until the connection is restored (after 6

minutes or if the same fault has occurred three times within 6 minutes, this input

will be interlocked).

20 - 21 Lockout input (240 V). If the connection between these terminals is interrupted

the boiler will lockout. Reinstate the connection and press reset.

30 - 31 External sensor* (2-wire 1,01 kΩ PTC). After a suitable sensor has been connected

it will be automatically recognised when the power supply is switched on.

32 - 33 Low velocity header sensor* (2-wire 1,01 kΩ PTC). This sensor can measure the

temperature of a low velocity header.

35 - 36 Calorifier temperature sensor* (2-wire 1,01 kΩ PTC). After a suitable sensor

has been connected it will be automatically recognised when the power supply

voltage is switched on. The terminals 34 - 35 must not be interconnected. The

purpose of this function, in comparison with the calorifier thermostat, is to make

possible a night time temperature reduction and an anti-legionella switching

(only with BME, E6 or KKM).

37 - 38 External influence* (2 – 10 VDC = +10°C – +90°C). At voltages below 2 V the

boiler will switch to “constant supply temperature operation”.

39 - 40

Output capacity signal*. This signal provides information for a capacity display.

0 – 100% = 0 – 10 VDC. The maximum current is 5 mA.

For higher currents or long connecting wires (›5 m) the use of a signal amplifier is

recommended.

41 - 42 SCOM bus connection (use the correct polarity).

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43 - 44 Primary boiler pump control (0 – 10 V = +2°C – +90°C). * the use of screened cables

is recommended.

5.3.3 Water connections

The appliance must be installed by a recognised installer in accordance with the applicable national

and local specifications and regulations. The flow and return connections are made at the rear of the

unit.

Supports for water connections

It is recommended that the flow and return pipes be properly supported. This will avoid damage

through overloading (weight) and simplifies maintenance.

The unit is a constant water flow appliance and is only suitable for use on closed pre-pressurised

systems.

The unit is fitted with a boiler pump as standard and which guarantees the required water circulation

through the boiler. The capacity and working head of the pump is sufficient to overcome both the

resistance of the boiler and some resistance offered by the system.

The boiler pump is however not a system pump

If the resistance of the system exceeds the available working head, the boiler will be shut down

by the flow switch. In order to prevent this happening, the length and diameter of the primary

pipework between the boiler and the low velocity header must be chosen such that the remaining

working head of the pump (see table 12) will not be exceeded.

It is recommended that manually operated valves be fitted between the water connections and

the installation.

In order to limit the losses occurring in a non-operational boiler, a motorised valve can sometimes

fitted in the flow or the return pipe or a mechanical non-return valve is used for this purpose.

Standby losses can be reduced even further by shutting down the boiler via the boiler enable

terminals. A properly dimensioned low velocity header ensures that the natural flow through the

boiler can be neglected

.

5.3.4 Combustion air supply

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5.3.4.1 General

The unit can optionally be supplied as a room sealed appliance. This simplifies the possibilities

for installation within the building.

Guide lines and installation instructions

The flue gas discharge and the air supply systems must be installed by a recognised installer in

accordance with the applicable national and local specifications and regulations.

The total resistance of the air supply and the flue may not result in a pressure drop exceeding

1.0 mbar.

5.3.4.2 Air supply pipe

The air supply pipe may be single-walled and constructed of:

- plastic

- thin-walled aluminium

- flexible aluminium (take account of the resistance).

Type Air supply X Y

diameter D (mm) (mm) (mm)

318

200 160 220

376

200 160 220

443

250 240 240

508

250 185 240

559

250 185 240

624

250 239.5 359

730

300 239.5 266

826

300 239.5 266

923

355 289.5 266

1018

355 233.5 266

Fig. 18 horizontal air supply

Fig. 19 Air supply connection

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The connection to the air supply pipe is always mounted on the top of the unit.

Multiple units may not be connected to the same air supply or flue pipe.

To prevent snow entering, the air supply pipe must extend at least 30 cm above the roof and must

be fitted with a rain cap.

The flue pipe opening must end at least 100 cm above the roof, assuming the roof to be flat.

Fig. 20 Heights of air inlet and flue gas discharge

The relative horizontal difference between the flue pipe the air supply pipe must not be less than

the width of the unit.

Fig. 21 Distance between air inlet and flue gas outlet

The formation of unwanted condensation must be avoided. In the event that during the heating up

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period condensation occurs, the condensate must be able to flow back to the unit. Inspection of

the air supply and flue pipe must be possible.

The connection, exit position and height in relation to possible obstacles must comply with the

applicable national and local standards and regulations.

5.3.5 The flue system

5.3.5.1 General

The flue pipe connection is at the rear of the appliance and has been designed for direct connection

to a corrosion resisting flue pipe.

Condensation forms because of the high boiler efficiency and the considerable degree of cooling

of the flue gasses that takes place against the walls of the flue pipe. In order to reduce flue gas

condensation as much as possible, the use of a double-walled and insulated flue pipe is

recommended.

Aluminium or stainless steel is strongly recommended. Because a slight overpressure exists in the flue

pipe during a cold start-up, flue pipes should preferably be constructed from seamless materials.

When the boiler functions as a high capacity boiler, the high efficiency can lead to the formation of

condensation in the chimney.

The condensate drain must never become blocked!

Direct connection to brick built stacks is not permitted because the combustion efficiency of the

boiler is › 83%. The combustion products at low flue gas temperatures will damage the stack.

The following table lists all the flue gas data for all types of boiler.

Type Flue gas Flue gas quantity at full capacity Maximum

temperature at

permissible

full capacity

chimney

(approx.)

resistance

°C m3/h kg/s mbar

318

140 637 0.156 1.0

376

140 757 0.186 1.0

443

140 858 0.208 1.0

508

140 1018 0.249 1.0

559

140 1118 0.275 1.0

624

155 1287 0.306 1.5

730

155 1505 0.357 1.5

826

155 1703 0.404 1.5

923

155 1901 0.451 1.5

1018

155 2099 0.498 1.5

Table 9 Flue gas data

Capacity 100%

Flow temperature 80°C

Return temperature 60°C

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5.3.5.2 Chimney
Chimney length

Because the appliance is fitted with a “premix burner” with a fan, an over-pressure is built up in the

unit. This overpressure is sufficient to overcome the resistance of the cooled burner, heat exchangers,

air intake and chimney up to a maximum of 1 mbar (318-559) 1.5 mbar (624-1018) external to the

boiler.

The back-pressure outside the unit depends on:

a The resistance of the flue pipe

b The degree of cooling of the burner system

c The resistance of the discharge system.

The degree of cooling of the flue gasses depends on:

a the insulation value of the chimney

b the local ambient temperature

c the discharge system.

The flue connection diameters of the units have been chosen such that the speed of the flue gas

will always be approximately 4.7 m/s. For the appliance there will be a maximum overpressure of

approximately 1.0 - 1.5 mbar (100 – 150 Pa) for the flue system (see table 10 for lengths).

Owing to their high resistance, bends with an R/D ratio smaller than 1 should be avoided. It may

happen that these must be used, in which case the chimney length must be calculated with the

aid of table 11. We advise fitting the horizontal pipe section with a fall so that any condensate

formed can be drained via the boiler.

The flue system attached to the Ultramax range of boilers must be designed to overcome its own

resistance and provide a draught at the appliance flue connection of between 5 to 15 Pa.

Fig. 22a Chimney connection

The Ultramax boiler must never be connected to a flue systems with a plastic lining

(consult the applicable standards and regulations). The maximum flue gas temperature at full

capacity and with a water supply temperature of 80°C will not exceed 160°C.

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The boilers are equipped with a flue attenuator.

Never connect the flue pipe directly to the flue attenuator.

The flue attenuator must always be free standing. It must never be in contact with the walls of the

chimney. The flue pipe connected to the appliance must first rise vertically by 70 cm before either

the diameter or the direction is changed.

The openings on the underside of the flue connection ring must never become blocked. The free

flow of condensate and any rain water must be guaranteed. The flue connection is at the back of

the appliance.

To ensure proper functioning of the appliance, it is recommended that a draught stabiliser be

mounted in the flue system.

Calculation of the diameter

For calculating and checking the internal diameter of a flue system with mechanical discharge,

refer to the applicable national and local regulations and specifications.

Calculation of the length

The lengths given in the following table are only intended for the further calculation of the total

length. The maximum vertical length may not exceed the flue length as indicated in table 10.

Maximum permitted flue system length in metres of smooth pipe. Standard flues only.

Type Length of flue system in m

Diameter Diameter Diameter Diameter Diameter Diameter Diameter Diameter

120 mm 150 mm 180 mm 200 mm 250 mm 300 mm 350 mm 400 mm

318

** ** ** 32 109* - - -

376

** ** ** 21 76* - - -

443

** ** ** ** 53 141* - -

508

** ** ** ** 38 105* - -

559

** ** ** ** 31 86* - -

624

** ** ** ** ** 115* 235 -

730

** ** ** ** ** 80 175* -

826

** ** ** ** ** ** 135* 265

923

** ** ** ** ** ** 110 200*

1018

** ** ** ** ** ** 100 175*

Table 10 Length of flue system

The flue system lengths have been rounded down.

* Chimney diameter at the appliance

** Not applicable

Losses in the chimney related to various chimney sections expressed in metres of straight pipe.

The total loss must be subtracted from the maximum permitted chimney length given in table 10.

Conversion for other types of accessories with different (resistance coefficient) values can be

simply accomplished by comparing with the stated losses at ζ =1.

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Type

Diameter

in mm

Ζ= 1

Elbow 90°

R/D = 1

Elbow 90°

right angle

Elbow 45°

ζ= 0,5

90° Tee ζ=

2

318 250* 6.2 3.1 8.1 3.1 12.4

200 4.5 2.2 5.8 2.2 8.9

376 250* 6.1 3.1 8.0 3.1 12.3

200 4.1 2.1 5.4 2.1 8.3

443 300* 7.0 3.5 9.2 3.5 14.1

250 5.5 2.8 7.2 2.8 11.0

508 300* 7.4 3.7 9.6 3.7 14.8

250 5.5 2.8 7.2 2.8 11.1

559 300* 7.3 3.6 9.5 3.6 14.6

250 5.5 2.7 7.1 2.7 10.9

624 300* 10 5 13 5 20

350 11 5 14 5 21

730 300* 9 5 12 5 19

350 11 6 14 6 22

826 350* 11 5 14 5 22

400 12 6 14 5 22

923 350* 11 6 14 6 22

400 12 6 15 6 24

1018 350* 12 6 16 6 24

400 13 6 16 6 25

Table 11 Chimney losses in metres of straight pipe

* Connection at boiler.

5.3.6 Condensate discharge

Condensate that forms in the appliance must be discharged to a drain.

If there is no direct connection to a drain present, a water collection tank with a pump and a level

switch may be used, so that the condensate can be pumped into a drain. The discharge of condensate

into roof guttering is not permitted.

The appliance is fitted with a water trap which prevents flue gasses from entering the boiler room.

The connection to the drain must be arranged such that there is an open connection under the

condensate discharge point on the appliance (see fig. 23). In addition, the discharge pipe must be

fitted with a trap (U-bend) in accordance with the applicable regulations.

Ensure that the distance between the condensate discharge point of the boiler trap and the drainage

pipe is at least 5 mm. This provides the required open connection and simplifies any subsequent

maintenance activities and inspections.

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Fig. 23 Condensate discharge

5.4 Hydraulic system

5.4.1 General

Although it is not the intention to provide a complete handbook covering the most divergent

hydraulic systems, the data is more extensive than would generally be provided in the case of

conventional central heating boilers.

The Ultramax units are low water content boilers for which the water flow rates must

be within minimum and maximum values. (∆t 15

0

C - 250C)

Table 12 - 14 lists the required relationship between the three parameters Q (water flow), P (pressure)

and t (temperature) at maximum capacity. Because of the high flow rate, the appliance is

less sensitive to water hardness. Therefore, the water hardness may not exceed 250 ppm with a

supply temperature of 80°C (see 5.4.5 Water quality).

5.4.2 Water flow

5.4.2.1 Flow rate and resistance

The rate of water flow through the appliance must never fall below the required minimum (otherwise

the water flow switch will be activated and the appliance will be shut down).

The use of valves, non-return valves, systems in which several appliances are connected to a

common transport system, etc., must not interfere with the required water circulation.

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∆T 20 K Pump data

Nominal
flow rate

Boiler­resis
tance

Grundfos pump

type

Pump
speed

Head at

Qnom.

Available
head at
Qnom.

Max.* power
consumption

Type

m

3/h kPa UPS

kPa kPa W

318

13.55 25 40-120F 3 55 30 460

376

16.08 30 50-120F 3 76 46 720

443

18.27 22 50-120F 3 70 48 720

508

21.59 27 50-120F 3 59 32 720

559

23.78 32 65-120F 3 83 51 1150

624

26.36 37 UPS 65-120F 3 80 43 1.15

730

30.83 25 UPS 65-120F 3 72 47 1.15

826

34.87 30 UPS 65-120F 3 60 30 1.15

923

38.96 35 UPS 80-120F 3 75 40 1.50

1018

43.00 40 UPS 80-120F 3 68 28 1.50

Table 12 Water flow rate and pump data

* The maximum power consumption of the pump is given for pump speed 3. The optimum operating point in relation to

efficiency and minimum power consumption can be determined from the related pump curve.

The primary pump has been sized to have an optimum duty when ∆T = 20 K. When running at ∆T’s

less than 20 K the pump size should be checked to ensure suitability.

The water flow rate can be adjusted with the aid of the built-in 3-speed pump control. The water

flow rate can be measured by making a ∆P measurement via the filling and drainage valve in the

supply and return pipe of the unit. The measured head can be compared with the boiler resistance

(table 12). At full capacity the water flow rate can be very accurately compared with the ∆T, measured

across the flow and return of the boiler.

The unit has a standard pump control. When the boiler is enabled, the pump is switched on. When

the enable signal is removed, the pump will continue to run for several minutes. This run on time

is adjustable. The standard time is two minutes.

When the system includes air heaters (ventilation, air treatment), it is usually desirable to have a

small ∆T over these components. Because of this, the quantity of water flowing through the total

secondary circuit is usually greater than that flowing through the boiler units.

The low velocity header must be dimensioned such that the water speed does not exceed 0.5 m/s.

In this case the diameter of the header must be calculated for the water volume flowing through

the secondary circuit. When the water volume flowing through the secondary circuit is greater

than that flowing through the primary circuit, a mixed temperature will exist which is lower than

the desired temperature of the supply from the appliance. The regulation system reacts to this

and opens the control devices (valves, etc.). Usually the supply temperature from the boiler(s)

must be adjusted to obtain the desired temperature in the connected circuits.

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5.4.2.2 Pump characteristics

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Type Pump Pmax Pmin I

cos

speed W W A

φ

3x400 V

UPS 40-120F
318 2 330 190 0.56 0.85

UPS 50-120F
376 – 508 2 530 300 0.94 0.81

UPS 65-120F
559 2 900 460 1.45 0.90

UPS 65-120F
624 – 826 2 900 460 1.45 0.90

UPS 80-120F
923 - 1018 2 1100 760 1.80 0.88

Table 13 Electrical data for pumps

5.4.2.3 Isolating valves

It is recommended that manual valves be fitted between the flow and return connections and the

installation.

5.4.2.4 Valves

For Ultramax units connected in cascade, a delayed motorised shut-off valve can be

used if it is controlled by the boiler using terminals 14 + 15 or alternatively, a mechanical non-return

valve can be used. This is required so as to avoid short-circuiting the appliance on the water

side.

5.4.2.5 Water flow protection

The unit is provided with water flow protection. This shuts the appliance down in the event that

the flow of water through the appliance falls below the minimum required value. This protection is

implemented by means of a water flow switch.

5.4.3 Water pressure

5.4.3.1 Operating pressure

At a maximum supply temperature of 90°C and a minimum water flow rate such as occurs at a ∆T

of 20 K, the minimum operating pressure must be greater than 1.5 bar. The operating pressure

must be measured with the pump switched off. If a lower pressure is desired, the maximum supply

temperature must be adjusted accordingly.

Minimum operating Flow temperature

∆T

pressure in bar

°C

K

›1.5 90 20

›1 80 20

Table 14 minimum operating pressures

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5.4.3.2 Boiler expansion tank

It is possible to fit an expansion tank in the return pipe between pump and the boiler isolating

valve.

5.4.3.3 System expansion tank

The size of the expansion tank is determined by the quantity of water in the system. Our advice is

to fit the system expansion tank at the neutral point (centrally) of the low velocity header.

5.4.3.4 Water pressure protection

All appliances are fitted with a safety valve that opens at 3 bar. As an option, safety valves can be

supplied with settings between 3 and 6 bar with increments of 1 bar.

5.4.4 Water temperature

The maximum permissible temperature of the water flow can be set at 90°C. If the high limit
thermostat functions at 100°C, the appliance shuts down and locks out and does not restart

automatically when the temperature falls below the high limit temperature setting.

5.4.5 Water quality

The composition and quality of the system water has a direct influence on the performance of

the whole system and the life of the appliance. Unsuitable addition and use of chemicals, water

softeners, oxygen binders, de-aerators, aerators, and water filters all increase the possibility of

faults.

Corrosive elements in certain additives can attack the system, resulting in leakage; deposits of

undesirable sediments can lead to damage to the boiler heat exchanger.

For water hardness, a distinction must be made between:

a Temporary hardness

This is also referred to as carbonate hardness. Deposits are formed at higher temperatures and

are easy to remove.

b Permanent hardness

Minerals (for example, calcium sulphate) dissolved in the water can be deposited as a function

of very high surface temperatures.

In the United Kingdom, water hardness is expressed in mg/litre (ppm) and is given the following

divisions:

Very soft less than 50 ppm

Soft approx. 50 - 160 ppm

Moderately hard approx. 160 - 250 ppm

Hard and very hard over 250 ppm

The system must contain soft to moderately hard water with a water hardness not exceeding
250 ppm with a supply temperature of 80°C and ∆T = 20 K.

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Before the water is topped up, the hardness and the chloride content of the water must be determined.

During the construction of larger installations, one of the appliances may be operational. New

circuits may be regularly switched in, which must occur together with the addition of fresh water.

In addition, it can happen that, because of leakage, some circuits must be disconnected, repaired

and re-filled. In these circumstances the only appliance in operation often functions at full capacity

and the chance of boiler scale formation is present. For this reason the make-up water must be

softened. To ensure proper functioning of the appliance and the system, the use of water softeners

is recommended.

Large stationary bubbles with widely different compositions can form at “dead points” in the

system (in addition to oxygen and nitrogen, hydrogen and methane have also been detected).

Oxygen promotes corrosion. Corrosion products, together with other pollutants, form a sludge

deposit (magnetite) which causes pitting under the influence of oxygen.

The use of an air separator with an automatic de-aerator is strongly recommended. This should

preferably be fitted in a horizontal section of the return pipe to the pump. If a vertical low velocity

header is employed, the air separator should be fitted above the header.

The chloride concentration must not exceed 200 mg/l. If this level is exceeded, the cause must be

located.

Compare the chloride concentration of the additional water with that of the system water.

If this concentration is higher, this indicates evaporation if no chloride containing materials have

been added. If chloride is present in high concentrations the water will be more aggressive (due

to, among other things, incorrectly regeneration of the water softener). The system must then be

flushed out and re-filled with low chloride content water.

To reduce the effects of unnecessary wear and blockages resulting from any pollution present we

advise the use of a filter system with a mesh opening of 100 microns. Always fit this in the return

pipe of the secondary part of the system.

It is imperative that the system is treated with suitable corrosion and scale inhibitors. The

concentration of the dosage must be monitored and maintained on a regular basis. Failure to comply

with these requirements will render the appliance warranty null and void.

In order to guarantee a well functioning system and a long life, any suspended and corrosion

producing particles must be removed with the aid of a well chosen and fitted filter system.

The analysis of system water and the cleaning of filters must form part of the periodic inspection

procedure.

5.4.6 Examples of hydraulic systems

The hydraulic systems shown are only examples. They must not be employed in practice without

professional analysis.

Low velocity header

The low velocity header must be dimensioned such that at full capacity the pressure difference

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between the supply to the flow and the return collector does not exceed 50 mmwg (approximately

0.5 m/s). The diameter of the low velocity header can be determined using the formula:

Where:

= the diameter of the low velocity header in m

Q = the water flow rate in m

3/h of the boiler circuit or the secondary circuit, whichever is

the greater.

v = the speed in m/s.

Example of a low velocity header with isolating valves and an expansion tank.

Mounting the low velocity header vertically has additional advantages: the upper section
functions as an air separator and the lower section serves as a dirt separator.

When air heaters (for ventilation or air treatment) are included in the system it is generally desirable

to have a small ∆T over the air heaters. Because of this, the water flow rate through the whole

secondary circuit is usually greater than that through the boilers.

The low velocity header must be so dimensioned that the water speed does not exceed 0.5 m/s.

In this case the diameter of the low velocity header must be calculated on the basis of the water

flow through the secondary circuit. Because the volume of the water in the secondary system is

greater than that in the primary circuit (boiler), there will be a water circulation in the opposite

direction to that of the primary circulation through the low velocity header. A mixed temperature

will then exist which is lower than the supply temperature from the boiler. The regulation system

will react to this and will open the regulator functions (valves, etc.) in the system. Generally, the

temperature of the water supply from the boiler(s) will need to be corrected to obtain the desired

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temperature in the connected circuits.

Systems with a separate flow header and a return header

Flow headers in combination with return headers are often used in renovation projects. Several

circuits operate with mixing valves or diverting valves. In both cases a low velocity header or a

bypass is necessary.

Fig. 28 Boiler with vertically mounted low velocity header arranged with right hand connections

Low velocity header with multiple heating circuits in a mixing control arrangements without a main pump

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Installations with multiple appliances

For installations in which each appliance is fitted with a pump, the pump is switched off after the

boiler has been shut down.

Fig. 29 Installation with multiple appliances

Hydraulic short-circuit

In order to avoid a short circuit over a non-operating appliance, we advise the use of non-return

valves. These may be either mechanically or electrically operated valves (see 5.4.2.4).

Installations with multiple appliances without non-return valves

The total resistance of the system (boiler, isolating valves and pipework) will be much greater

than the resistance of the low velocity header. The baffles “X” (see fig. 30) prevent undesirable

circulation through the non-operating boiler.

When two appliances are switched in cascade, it is advisable to employ this system. When appliances

are controlled by a building optimising system using weather compensation or a compensating

unit, the common flow temperature sensor must be mounted at the common flow pipe

as indicated in the drawing.

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Fig. 30 Installation with more than one appliance, without non-return valves and making use of a low velocity header for two boilers

Fig. 31 Low velocity header for two boilers

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6 Operating instructions

6 .1 Function

When a heating demand is received and before the boiler starts up, the appliance must be prepurged.

The fan supplies combustion air and has a modulating control.

A zero controller in the gas valve determines the required quantity of gas.

Gas and air are optimally mixed.

Thereafter, the gas air mixture is ignited on the main burner.

The fan also ensures that the resulting flue gasses are subsequently removed.

The removal system for these gasses performs an essential function for the proper operation of the

appliance.

The unit has no limits for return water temperature. If this temperature is low, condensation will

be formed which will then be removed via the drainage system.

6.1 Function
When a heating demand is received and before the boiler starts up, the appliance must be prepurged.

Gas and air are optimally mixed in the mixing chamber. The fan supplies air for combustion, the

quantity being regulated by the frequency controlled fan speed. A proportional controller determines

(also by means of regulation) the required quantity of gas. Thereafter, the gas air mixture is

ignited on the main burner. The fan also ensures that the resulting flue gasses are subsequently

removed. The removal system for these gasses performs an essential function for the proper

operation of the appliance.

The unit has no limits for return water temperature. If this temperature is low, condensation will

be formed which will then be removed via the drainage system.

Frequency Inverter Lenze

The Frequency inverter is used by the boiler control system to control the burner fan speed and

thus the heat output of the boiler.

The operating state is displayed by the 2 LEDs on the front of the unit.

LED display Operating state

Green Red

On Off Frequency regulator enabled

On On Mains connection and automatic start

Flashing Off Frequency regulator inhibited

Off

Flashing every
second

Fault indication

Off Flashing every

0,4 second

Under voltage

Off Off Mains voltage too low

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6 .2 Regulation

Depending on the heating demand, the unit will be started up and shut down between 0% and

25% capacity and will be continuously modulated between 25% and 100% capacity.

6.3 Control module

Lid closed Lid open

1 Function 1 Parameter indication

standby P1 current/setting boiler supply temp.
automatic operation P2 current/setting domestic hot water

summer operation temperature

service operation *P3 desired temperature

2 Function selector P5 current external temperature

3 fault indication

P8 current low velocity header temp.

4 supply temperature P9 current/maximum boiler capacity

5 malfunction code (flashing) P10 password entry for factory settings

6 operation mode 2 optical I/O

night time reduction (no heating demand) 3 reset/programming push-button

heating mode (heating demand) 4 alarm LED
(flashing) burning 5 parameter/value selector

6 output status

7 current/desired parameter value

8 fault/parameter indication

9 input status

* P3 set load (in combination with KKM)

Operating mode (cover closed)

With the cover closed and by using the rotational switch (pos. No. 2) clockwise or anti-clockwise

the boilers’ operating mode can be set.

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The operating modes are:-

standby the boiler switched off but frost protection is active
automatic the boiler can operate in heating or hot water mode
summer mode the boiler will only react to a hot water demand

service, low capacity the boiler will run at low capacity (adjusted by [P17])

service, high capacity the boiler will run at full capacity (adjusted by [P19]).

Information mode

With the cover open and by turning the rotational switch (Pos. No 5) clockwise or anti-clockwise it

is possible to read out certain information from the boiler management unit.

There are 10 possibilities. An arrow at the bottom of the LCD display will indicate which parameter

has been selected. The following parameters are readable:-

Parameter

P1 actual/setting flow temperature

P2 actual/setting direct hot water temperature (if used)

P3 set point temperature (* P3 set load in comb. with KKM)

P5 actual outside temperature (if used)

P8 temperature at the low velocity header (if used)

P9 actual / setting boiler capacity

P10 only for MHS trained service engineers.

Summary of input and output indications (cover open)

Input indications: -

Flame Ionisation detected

SW Water flow switch in operating position

DW Air Pressure Switch in operating position

RT Boiler enabled by BMS

Bus Data-bus detected.

Output indications: -

Power to Main Gas Valve
Power to Ignitor

Control signal to fan

Power to Primary Boiler Pump

Power to Primary DHW Pump.

Setting the flow temperature for Central Heating (cover open)

Only applicable to boilers without weather compensated flow temperature or a 0 - 10 Volt control

signal.

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- Open the lid (the arrow at the bottom of the LCD display indicates parameter P1)

- Push the Reset/Programming key (pos. 3), the LED will light, turn the rotary switch (pos. 5)

until the desired water flow temperature has been reached

- Push the Reset/Programming key, the LED will go out

- Close the cover.

Setting the flow temperature for Domestic Hot Water (cover open)

- Open the lid

- Turn the rotational switch (pos.5) clockwise until the arrow at the bottom of the LCD display

indicates parameter P2

- Press the Reset/Programming key (pos. 3), the LED will light, turn the rotary switch until the

desired Domestic Hot Water flow temperature has been reached

- Push the Reset/Programming key, the LED will go out

- Close the cover.

6.4 Fault indications

A fault always results in a flashing

symbol and a fault code appearing in the display. When a

fault occurs, the cause must always be found and corrected before the related protective function

is reset. The operating signal (terminals 12 - 13) falls off if a fault has occurred more than 2 times

within 6 minutes (the fault code will appear in the display with a “3”) or if a fault is longer than 6

minutes active. The boiler can be nevertheless in operation.

1 The high limit thermostat has operated. The boiler temperature has exceeded 100°C. Press

the reset button.

2/3 The interlocking input has been interrupted. Correct the external error and press reset.
4 Flame signal fault. No flame detected at burner start. One restart possible. Correct fault and

press reset.

5 Flames go out during operation. If this fault occurs 3 times within 6 minutes, the fault becomes

interlocking. Correct the fault and press reset.

6 Temperature protection has operated. The boiler temp. has exceeded the setting. Press

reset.

7 The lockout input has been interrupted. Correct the external fault and press reset.
11 Error in flame signal. A flame has been detected during start-up. Correct the fault and press

reset.

12 Flow temperature sensor is faulty. Correct fault.
13 Wiring of the CXE/EM extension module is defective. Correct fault.
14 Hot water temp. sensor is defective. Correct fault.
15 External temp. sensor is defective. Correct fault.
18 Header temp. sensor is defective. Correct fault.
20 Error in the control of gas valve 1. After burner has stopped a flame has been detected for a

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period of 5 seconds. This in spite of the fact that valve has been sent a close signal. Correct

fault.

21 Error in the control of gas valve 2. After burner has stopped a flame has been detected for a

period of 5 seconds. This in spite of the fact that valve has been sent a close signal. Correct

fault.

22 Air flow too low. The air pressure switch has not operated during pre-purge. Correct fault

and press reset.

23 The air pressure switch has not switched off. Press reset.
24 The fan does not reach the set speed during pre-ventilating. Correct fault.
25 The fan does not reach the set speed during ignition. Correct fault.
26 The fan does not come to a standstill. Correct fault.
27 The air pressure switch switched off during operation.
30 CRC error in EEprom data group “Boiler”. Press reset.
31 CRC error in EEprom data group “Burner”. Press reset.
32 Fault in 24 V circuit. Correct fault.
40 Error detected in the position of the flow switch. Correct fault.
X.Y. An internal fault has been detected during the self-test. Press reset.

6 .5 Start-up

1 Open the gas valve

2 Switch on the appliance using the on/off switch on the control panel

3 Select the function “automatic operation

” using the function selector. (See also the

operating instructions on the boiler).

6 .6 Shut-down

The unit can be shut down in three different ways:

A The boiler continues to supply domestic hot water. Select the

function with the function

switch

B The boiler is not operating and will only start up for automatic frost protection. Select the

Function using the function selector

C Shut down the boiler:

1 Switch off the boiler using the on/off switch on the control panel

2 Close the gas valve.

6 .7 Warnings

The unit must be installed by a recognised installer. The operating instructions must be strictly

observed.

If the source of the fault cannot be found, the service organisation must be contacted. Never

repair the appliance yourself.

The condensate drain may never be modified or closed off. When a boiler is completely shut down

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in the winter period, there is a danger of freezing. Drain the water out with the aid of the filling/drainage

valve. The user must never make any modifications to the appliance or the discharge

system.

Annual checking and good maintenance are necessary in order to guarantee optimum performance.

7 Commissioning

7.1 General

Commissioning must be carried out by skilled personnel. Failure to observe this condition will

invalidate the guarantee.

Commissioning of the unit by MHS Boilers Ltd will not only ensure optimum operation of the unit but

will enhance the warranty enjoyed by the unit.

7.2 Commissioning
Water and the hydraulic system

The system water circulating around the boiler must be treated with a suitable / proprietary scale and

corrosion inhibitor.

Failure to comply with these requirements will invalidate the appliance warranty.

The total hardness of the system water must be below. 250 ppm.

In addition to the introduction and repeated monitoring of the scale and corrosion inhibitor the Chloride

concentration of the system water must never exceed 200 mg/l.

Failure to comply with this requirement will invalidate the appliance warranty.

Check the pressure of the system water. This must have at least the minimum value given in table

14(Operating pressures).

Check that there is a suitably sized by-pass or a low velocity header fitted in the hydraulic system.

Check and bleed the pump

Switch on the power supply to the boiler at the on/off switch and check the direction of rotation of

the boiler pump after removing the end cap from the pump motor housing.

Before the appliance is started up, any air present must be bled out of the pump by removing the

end cap from the pump motor housing. This must be repeated after the appliance has been in

operation for a short time.

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Check the chimney

Check the chimney. Ensure that the connection between the appliance and the chimney is such

that gasses cannot escape. The flue must be connected to outer white flexible seal and not the inner

vertical extension.

Bleed the gas pipework

Open the gas valve. Check that the gas piping is gas-tight. Remove any air between the gas valve

and the appliance.

Check the operation of the appliance at full capacity

Start up the appliance. Allow the appliance to operate at full capacity and to stabilise (approximately

3 minutes). At full capacity, the following settings must be checked and corrected if necessary

using the butterfly valve on the mixing chamber, The V-adjust screw on the gas valve, should not

normally require adjusting.

Guide valves V: Kromschroder gasvalves 1.2 - 1.5 Dungs gas valves 0.94

Natural Gas

Pilot burner CO2 (Types 624–1018) [%] 10.0 ± 0.2

Pilot burner CO (Types 624–1018) [ppm] ≤ 1000

Main burner CO2 [%] 10.0 ± 0.2

Main burner CO [ppm] ≤30

Burner pressure pfan– pabove burner (Types 318–559) [mbar] 8.5 ± 1

Burner pressure pfan– pabove burner (Types 624–1018) [mbar] 9.0 ± 1

Propane

Pilot burner CO2 (Types 624–1018) [%] 11.0 ± 0.2

Pilot burner CO (Types 624–1018) [ppm] ≤ 1000

Main burner CO2 [%] 11.0 ± 0.2

Main burner CO [ppm] ≤ 30

Burner pressure pfan– pabove burner (Types 318–559) [mbar] 8.5 ± 1

Burner pressure pfan– pabove burner (Types 624–1018) [mbar] 9.0 ± 1

Table 15 Settings at full capacity

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Burner pressure measurement Type 318 - 559

Burner pressure measurement Types 624 - 1018

Measure the gas pressure at the supply side of the gas valve. This must be at least 18 mbar (for

natural gas) with the boiler operating at full capacity. When multiple appliances are installed in

the boiler room, this pressure must be measured with all the appliances operating at full capacity.

Check the temperature difference (∆T) between the flow and return to the appliance at the water

side. ∆T must be at full capacity between 15 and 25 K at full capacity.

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Check the appliance at minimum capacity

Adjust the appliance to operate at minimum capacity. At minimum capacity the following settings

must be checked and corrected if necessary only using the N-adjust screw on the gas valve.

Natural Gas

Pilot burner CO2 (Types 624–1018) [%] 10.2 ± 0.2

Pilot burner CO (Types 624–1018) [ppm] ≤ 1000

Main burner CO2 [%] 9.2 ± 0.2

Main burner CO [ppm] ≤ 30

Burner pressure pfan– pabove burner (Types 318–559) [mbar] 0.8 ± 0.1

Burner pressure pfan– pabove burner (Types 624–1018) [mbar] 0.7 ± 0.1

Propane

Pilot burner CO2 (Types 624–1018) [%] 11.2 ± 0.2

Pilot burner CO (Types 624–1018) [ppm] ≤ 1000

Main burner CO2 [%] 11.0 ± 0.2

Main burner CO [ppm] ≤ 30

Burner pressure pfan– pabove burner (Types 318–559) [mbar] 0.8 ± 0.1

Burner pressure pfan– pabove burner (Types 624–1018) [mbar] 0.7 ± 0.1

Table 16 Settings at minimum capacity

Setting air pressure switch: 0,4 +

} 0,05 mbar

Check the function ∆P

min pressure switch by carefully placing a board (for example, a piece of

strong cardboard) in front of the supply opening to the fan and slowly slide the board so as to

close off the opening until the boiler shuts down.

If the appliance is checked in the manner indicated, and corrected as necessary, the following

pressures, at full capacity, must be recorded for reference on the commissioning report note:

P

vent

Pbb

Pvent-Pbb (measure separately!)

P

vh

∆T

8 Maintenance

8 .1 Safety

During maintenance activities, always wear suitable clothing and shoes. Consider your own

safety, particularly in respect of jewellery and loose clothing.

8.2 General

In order to ensure continued good and safe operation of the appliance, this must be inspected at

least once per year.

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The following activities must be carried out (for an extensive description of these activities, see

8.3):

- Renew the ignition and ionisation electrodes

- Clean the air inlet damper

- Clean the fan blades

- Clean the flue gas collection chamber

- Clean the condensate trap and the drainage pipe from the appliance

- Clean the gas filter

- Inspect all pressure measurement pipes and nipples.

- After removing the panels from the left hand side of the appliance, ignition and burning can be

observed from both front and rear via a sight glass.

- Test the unit at the flue gas side for CO

2 and CO and correct these at both full and minimum

capacity if necessary.

- Check all the safety functions, and make any necessary adjustments.

- Measure the water temperature difference ∆T as a measure of the flow rate.

- Check the water pressure

- Check the water quality: Scale and corrosion inhibitor concentration, hardness and chloride content

- Record all data

- Clean the outside of all the panels and ensure that these all have a smart appearance.

8.3 Procedure

a) Disconnect the power supply

b) Close the gas supply valve

- The ignition and ionisation electrodes are fitted at the rear of the appliance.

- Remove the spark plug caps from the ignition and ionisation electrodes and inspect them for

possible damage, such as indications of burning or pollution (renew the spark plug caps if damaged).

In order to carry out the following activities, the panels must first be removed.

-In order to clean the air inlet damper this must first be re moved. Clean it with a vacuum cleaner.

- For appliances installed in a dusty environment, the fan blades may become dirty. This will

result in the air supply being reduced and the fan becoming unbalanced. Clean the fan blades

with a brush. All loose dirt can be removed in this way.

-A trap is fitted under the condensate collection tank. Unscrew the trap and clean it.

-A gas filter is fitted at the start of the gas train.

This filter can be cleaned as follows:

1 Close the gas valve on the boiler

2 Unscrew the six bolts securing the cover to the gas filter

3 Carefully remove the filter element

4 Clean the filter element by shaking it. When it is heavily polluted, the filter element must be

renewed.

5 Re-assemble the filter

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6 Check for leaks (soap solution).

- Inspect all the pressure measurement pipes. Ensure that these are securely fastened and

tighten the connection nuts if necessary.

- Inspect the screws in the measuring nipples; renew the measuring nipples if they have become

damaged.

- In order to measure gas and air pressures and to perform measurements at the flue gas side,

calibrated test equipment must be employed.

- All test data must be recorded on the applicable test forms.

8.4 Cleaning the burner and heat exchangers

Only in exceptional circumstances (In relation to severely contaminated supply air) the burner and the

heat exchangers can be cleaned internally with suitable media. This must only be undertaken by

qualified MHS engineers. Failure to comply with this will invalidate all appliance warranties.

8.5 Cleaning the filter/screen in the gas combination block

In order to clean the filter/screen in the gas combination block, this must first be removed.

Kromschröder gas combination block

1 Close the gas supply valve to the boiler

2 Release the gas train by unscrewing the top bracket from the mixing system

3 Unscrew the four bolts securing the input flange

4 Remove the filter from the combination block

5 Remove any dirt by tapping the filter

6 Re-assemble the filter in the reverse order

7 Check for leaks (soap solution).

Dungs gas combination block

1 Close the gas supply valve to the boiler

2 Unscrew the bolts from the input and output flange, while supporting the gas valve

3 Carefully remove the gas valve from between de flanges

4 Clean the sieve

5 Re-assemble the gas valve

6 Check for leaks (soap solution).

8.6 Ionisation measurement

In order to carry out an ionisation measurement, a micro-ammeter with a measuring range of 0

- 200 µA DC must be connected in the ionisation circuit. In this way the ionisation protection function

can be checked. The nominal ionisation current is between 6 and 25 µA.

The minimum ionisation current is 2.8 µA.

8.7 Replacing the frequency Inverter

Each boiler is factory tested and adjusted to run at the desired maximum output. The frequency

set in code CO11 allows the boiler to modulate up to but not higher than this maximum output and

is specific to the boiler.

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If the frequency Inverter has to be replaced then it must be pre programmed with this setting at

the factory.

ALWAYS QUOTE THE BOILER SERIAL NUMBER to enable this to be done.

Factory set parameters Frequency Inverter

CO11 Max. field frequency Boiler specific
CO12 Acceleration time 15 sec.

CO13 Deceleration time 15 sec.
CO14 Control mode 1 (quadratic)
CO15 V/f rated frequency 70 Hz

8 .8 Service

For service and maintenance the Technical Service Department of MHS Boilers Ltd can be contacted

on 01268 546700.

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Notes

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