VOKERA Compact A, Compact A Series, Compact A 25, Compact A 29 User Instructions

40

Users Instructions

Installation &
Servicing
Instructions

THESE INSTRUCTIONS
TO BE RETAINED
BY USER

Vokèra is a licensed member of the Benchmark scheme
which aims to improve the standards of installation and
commissioning of domestic hot water systems in the UK.

Compact A

High effi ciency combi boiler

Compact A 25 G.C. N° 47-364-17

Compact A 29 G.C. N° 47-364-18

38

Users instructions

Things you should know Page

1.1 Gas appliances 1

1.2 Electrical supply 1

1.3 Guarantee registration card 1

1.4 Appliance Log Book (UK only) 1

1.5 How does it work? 1

1.6 Dimensions 1

1.7 Clearances required 1

1.8 Frost protection system 1

1.9 Appliance status indicators 1

Getting started Page

2.1 Before switching ON 3

2.2 Appliance controls 3

2.3 Lighting the boiler 3

2.4 Adjusting the heating temperature 3

2.5 Adjusting the hot water temperature 3

2.6 Explanation of features 3

2.7 Automatic temperature control 3

How to... Page

3.1 How to top-up the system pressure 4

3.2 How to reset the appliance 4

3.3 How to shut down the system for short periods 4

3.4 How to shut down the system for long periods 4

3.5 How to care for the appliance 4

What if... Page

4.1 What if I suspect a gas leak 5

4.2 What if I have frequently top-up the system 5

4.3 What if the appliance is due its annual service 5

4.4 What if I need to call an engineer 5

Setting the Vokèra Page

5.1 Setting the Vokèra mechanical clock 5

Installation and Servicing instructions

Design principles & operating sequence Page

1.1 Principle components 7

1.2 Mode of operation (at rest) 7

1.3 Mode of operation (heating) 7

1.4 Mode of operation (Hot water) 7

1.5 Safety devices 7

Technical data Page

2.1 Central heating 8

2.2 Domestic hot water 8

2.3 Gas pressures 8

2.4 Expansion vessel 8

2.5 Dimensions 8

2.6 Clearances 8

2.7 Connections 8

2.8 Electrical 8

2.9 Flue details (60/100) 8

2.9A Flue details (80/125) 8

2.9B Flue details (twin pipes) 8

2.10 Effi ciency 9

2.11 Emissions 9

2.12 Pump duty 9

General requirements (UK) Page

3.1 Related documents 10

3.2 Location of appliance 10

3.3 Gas supply 10

3.4 Flue system 10

3.5 Air supply 10

3.6 Water circulation 10

3.7 Electrical supply 11

3.8 Mounting on a combustible surface 11

3.9 Timber framed buildings 11

3.10 Inhibitors 11

3.11 Showers 11

General requirements (EIRE) Page
3A.1 Related documents 11
3A.2 Location of appliance 11
3A.3 Gas supply 11
3A.4 Flue system 11
3A.5 Air supply 12
3A.6 Water circulation 12
3A.7 Electrical supply 12
3A.8 Mounting on a combustible surface 12
3A.9 Timber framed buildings 12
3A.10 Inhibitors 12
3A.11 Showers 12
3A.12 Declaration of conformity 12

Installation Page

4.1 Delivery 13

4.2 Contents 13

4.3 Unpacking 13

4.4 Preparation for mounting the appliance 13

4.5 Fitting the fl ue 13

4.6 Connecting the gas & water 17

4.7 Electrical connections 18

Commissioning Page

5.1 Gas supply installation 19

5.2 The heating system 19

5.3 Initial fi lling of the system 19

5.4 Initial fl ushing of the system 19

5.5 Pre-operation checks 19

5.6 Initial lighting 19

5.7 Checking gas pressure & combustion analysis 19

5.8 Final fl ushing of the heating system 19

5.9 Setting the fl ow outlet temperature 19

5.10 Setting the system design pressure 19

5.11 Regulating the central heating system 20

5.12 Final checks 20

5.13 Instructing the user 20

Servicing Page

6.1 General 20

6.2 Routine annual servicing 20

6.3 Replacement of components 20

6.4 Component removal procedure 21

6.5 Pump assembly 21

6.6 Safety valve 21

6.7 Lower automatic air release valves 21

6.8 Water pressure switch 21

6.9 Flow thermistor 21

6.10 Return thermistor 21

6.11 Printed circuit board 21

6.12 Gas valve 22

6.13 Electrodes 22

6.14 Flue fan & mixer 22

6.15 Burner 22

6.16 Main heat exchanger 23

6.17 Automatic by-pass & DHW non-return valve 23

6.18 Expansion vessel removal 23

6.19 Condense trap removal 23

6.20 Flue collector removal 24

Checks, adjustments and fault fi nding Page

7.1 Checking appliance operation 25

7.2 Appliance modes of operation 25

7.3 Checking the CO

2

& adjusting the valve 25

7.4 Combustion analysis test 26

7.5 Checking the expansion vessel 26

7.6 External faults 26

7.7 Electrical checks 26

7.8 Fault fi nding 27

7.9 Component values & characteristics 27

7.10 Adjustments 28

Wiring diagrams Page

8.1 External wiring 31

8.2 Typical control applications 31

8.3 Other devices 31

8.4 Vokèra lower cover mechanical clock 31

L.P.G. instructions Page

9.1 Related documents 33

9.2 Technical data 33

9.3 Converting the appliance gas type 33

9.4 Gas supply 33

9.5 Gas supply installation 33

9.6 Checking the CO

2

and adjusting the gas valve 33

Benchmark 35-36

Commissioning 37

1

USERS INSTRUCTIONS

1.1 GAS APPLIANCES

Gas Safety (Installations and Use) Regulations (UK).

In the interests of your safety and that of others it is a legal
requirement that all gas appliances are installed and correctly
maintained by a competent person and in accordance with the
latest regulations.

1.2 ELECTRICAL SUPPLY

Please ensure that this appliance has been properly connected
to the electrical supply by means of a double pole isolator or
un-switched socket, and that the correct size of fuse (3 AMP)
has been fi tted.

Warning: this appliance must be earthed!

1.3 GUARANTEE REGISTRATION CARD

Please take the time to fi ll out your guarantee registration card.
The completed warranty card should be posted within 30 days
of installation.

1.4 APPLIANCE COMMISSIONING CHECKLIST
(UK only)

A checklist section can be found at the rear of the appliance
installation booklet. This important document must be com­pleted during the installation/commissioning of your boiler. All
GAS SAFE registered installers carry a GAS SAFE ID card,
and have a registration number. These details should be re­corded in the Benchmark commissioning checklist section
within the installation booklet. You can check your installers
details by calling GAS SAFE direct on 08004085500. Failure
to install and commission the appliance in accordance with
the manufacturers instructions will invalidate the warranty.
This does not affect your statutory rights.

1.5 HOW DOES IT WORK?

Your Compact A boiler supplies heated water to your radiators
and hot water to your hot water taps.
The central heating is controlled via a time clock and any
thermostats that your installer may have fi tted. The boiler will
light when it receives a request from the time clock via any
thermostat that may be installed, or whenever a hot water
outlet (tap) is opened.
Your Compact A boiler lights electronically and does not have
a pilot light.
In the unlikely event of a fault developing with your boiler, the
supply of gas to the burner will be terminated automatically.

Dear Customer

Your Vokèra Compact A boiler has been designed to meet and exceed the very latest standards in gas central heating technol­ogy, and if cared for, will give years of reliable use and effi ciency.
Please therefore take some time to read these instructions carefully.

Do’s and Don’t’s

- Do ensure that the system pressure is periodically checked

- Do ensure that the boiler should not be used by children or unassisted disabled people

- Do ensure that you know how to isolate the appliance in an emergency

- Do ensure that you are familiar with the appliance controls

- Do ensure that your installer has completed the appliance log book section

- Do not attempt to remove the appliance casing or gain internal access

- Do not hang clothes etc. over the appliance

- Do not forget to have the appliance serviced annually.

This booklet is an integral part of the appliance. It is therefore necessary to ensure that the booklet is handed to the person re­sponsible for the property in which the appliance is located/installed. A replacement copy can be obtained from Vokèra customer
services.

INTRODUCTION

1.6 DIMENSIONS

1.7 CLEARANCES REQUIRED

1.8 FROST PROTECTION
SYSTEM

The Compact A is equipped with
a built-in frost protection system,
this enables the boiler to over-ride
the time controls – even if switched
off – and operate the burner and/or
pump, should the temperature drop
below 5

0

C for the main and for the
DHW line. In particular the burner
will be in ON status until the main
temperature reaches 35°C for CH
appliance and 55°C for DHW appli-

1. THINGS YOU SHOULD KNOW

Compact A 25-29

HEIGHT 715 mm

WIDTH 405 mm

DEPTH 250 mm

ABOVE 150 mm
BELOW 150 mm
LEFT SIDE 12 mm
RIGHT SIDE 12 mm
FRONT 600 mm

ance. Please note that the frost protection system is designed
to protect the appliance only, should frost protection be required
for the heating system, additional controls may be required.

NOTE

The frost protection system is reliant on the appliance having a
permanent electrical supply, and being in a non-fault condition.

1.9 APPLIANCE STATUS INDICATORS

Your boiler is equipped with a large LCD display that indicates
the appliance operating status.

2

MODE

SELECTOR SWITCH

HEATING

TEMPERATURE

SELECTOR

HOT WATER

TEMPERATURE

SELECTOR

PRESSURE GAUGE

DISPLAY

HOT WATER TEMPERATURE SELECTOR

Move the selector clockwise to increase the hot water outlet temperature, or counter-clockwise to reduce the temperature

PRESSURE GAUGE

Ensure the system pressure is set correctly (minimum 0.5-bar)

MODE SELECTOR SWITCH/HEATING TEMPERATURE SELECTOR

Mode selector switch:

Fig. 1

Hot water only - Select this position if you want the boiler to supply hot
water only (no heating)

Hot water temperature selector: move the selector clockwise to increase
the DHW outlet temperature, or counter-clockwise to reduce the temperature
(range: 37°C-60°C). The display shows the temperature values.

Boiler at OFF/standby - Select this position when you want the boiler to
be switched off for short periods (days) or if the boiler requires to be reset

The display shows “- -”.

Heating & hot water - Select this position when you want the boiler to re­spond to a heating and hot water request from the time-clock programmer

Heating temperature selector: move the selector clockwise to increase the
heating outlet temperature, or counter-clockwise to reduce the temperature
(range: 40°C-80°C for standard central heating).
The automatic temperature control function (SARA) is set within the blank
bullet points.
The display shows the temperature values.

Pressure gauge shows the current pressure of your heating system, the
gauge should be set between 1 and 1.5 BAR. When the appliance is oper­ating the gauge may rise or fall slightly, this is quite normal. The minimum
permissible level for the safe and effi cient operation of the appliance is 0.5
BAR. Should the pressure fall below 0.5 BAR, the boiler may lockout.

correct pressure

value

DHW pre-heat function - Turning the domestic hot water temperature
adjustment knob to the symbol activates the pre-heating function. Bring the
domestic hot water temperature adjustment knob back to the required po­sition. The activation of this function is indicated on display with the P icon
ON. This function keeps the water in the domestic hot water exchanger
hot, to reduce standby times when a request is made. The display shows
the delivery temperature of the heating water or the domestic hot water,
according to the current request. To deactivate the pre-heat function, rotate
the domestic hot water temperature adjustment knob back to the symbol.
Bring the domestic hot water temperature adjustment knob back to the
required position. This function cannot be activated when the boiler is OFF:
function selector to OFF position.

SARA function

3

DIGITAL DISPLAY

Fig. 2

Symbol/Icon Description

Displayed when heating mode is active

Displayed when hot water mode is active

Displayed when frost protection function is ac­tive

Displayed when hot-water pre-heat function is
enabled. Flashes when functioning

Displayed if an alarm or fault has been detected

Displayed when low system pressure has been
detected

Displayed when an external sensor is connected
to the boiler

Displayed if an ignition fault has been detected

65

2.1 BEFORE SWITCHING ON

Before switching the appliance on, please familiarise yourself
with:

- how to isolate the appliance from the gas, water, and electricity
supplies;

- how to check and top-up – if necessary – the system water
pressure;

- the time clock or programmer (if fi tted);

- any external thermostats and their functions;

- the appliance controls.

2.2 APPLIANCE CONTROLS (see fi g. 1)

The appliance controls are situated on the lower front of the
appliance. The appliance controls include:

- pressure gauge;

- appliance mode selector;

- temperature selector;

- optional integral time clock/programmer (if fi tted).

NOTE

The appliance frost protection is active in all the boiler modes.
The temperature selectors can be used to vary the temperature
of the water that circulates around your radiators and the water
that fl ows from your hot water taps. The temperature range is
adjustable between 40

o

C and 80oC for the central heating, and

between 37

o

C and 60oC for the hot water.
Refer to the main appliance status table for fault indicator and
boiler status.
The integral digital time clock is used to switch the heating on
and off at pre-determined intervals

2.3 LIGHTING THE BOILER

Ensure the gas and electrical supply to the boiler are
turned on.

Turn the mode selector switch to the ON position. When there
is a request for heating or hot water via the time clock or pro­grammer, the boiler will begin an ignition sequence. When the
appliance reaches the CH set temperature, the burner will go
off for a minimum period of approximately 3 minutes.
When the programmer/time clock or external thermostats
heating request has been satisfi ed, the appliance will switch
off automatically.

2.4 ADJUSTING THE HEATING TEMPERATURE

Rotate the temperature selector – clockwise to increase, counter­clockwise to decrease – to the desired temperature setting. The
temperature can be set from a minimum of 40°C to a maximum
of 80°C (if standard CH mode is selected).

2.5 ADJUSTING THE HOT WATER TEMPERA­TURE

Rotate the temperature selector – clockwise to increase,
counter-clockwise to decrease – to the desired temperature
setting. The temperature can be set from a minimum of 37°C
to a maximum of 60°C. If the temperature at the outlet is still
not suffi ciently hot enough, it may be necessary to reduce the
fl ow of water at the hot water outlet (tap).

NOTE

If the appliance fails to ignite during the ignition sequence, it
will enter a lockout condition. Should this occur, please allow

a period of at least two minutes before re-setting the appliance.

2.6 EXPLANATION OF FEATURES

Although the Vokèra Compact A has been designed for simplicity
of use, it utilises the latest in boiler technology, enabling a host

of functions to be carried out simultaneously.

2.7 AUTOMATIC TEMPERATURE CONTROL

The automatic temperature control function (SARA), permits the
boiler (when the heating temperature selector is set within the
blank bullet points) to automatically adjust (raise) the heating.
The activation and the disable of the function is visualized on
the display if the heating temperature is selected between
55° - 65°C.

2. GETTING STARTED

4

3.1 HOW TO TOP-UP THE SYSTEM PRESSURE
(fi g. 1-2)

The system pressure must be checked periodically to ensure the
correct operation of the boiler. The needle on the gauge should
be reading between 1 and 1.5 BAR when the boiler is in an off
position and has cooled to room temperature. If the pressure
requires ‘topping-up’ use the following instructions as a guide.

- Locate the fi lling valve connections (usually beneath the
boiler, see fi g. 3).

- Attach the fi lling loop to both connections.

- Open the fi lling valve slowly until you hear water entering the
system.

- Close the fi lling valve when the pressure gauge (on the boiler)
reads between 1 and 1.5 BAR (see fi g. 1).

- Remove the fi lling loop from the connections.

3.2 HOW TO RESET THE APPLIANCE

When the fault code is displayed, the appliance will require to
be reset manually. Before resetting the boiler, check what action
is required to be taken, using the information on the fault code
table below. Allow a period of two minutes to elapse before rotate
the mode selector knob across the position (see fi g. 1).

IMPORTANT

If the appliance requires to be reset frequently, it may be indica­tive of a fault, please contact your installer or Vokèra Customer
Services for further advice.

3. HOW TO...

Fig. 3

control

valve

temporary

connection

control

valve

supply pipe

double

check valve

fl ow/return

pipe

3.3 HOW TO SHUT DOWN THE SYSTEM FOR
SHORT PERIODS

The system and boiler can be shut down for short periods by
simply turning the time clock to the off position. It is also advis­able to turn off the main water supply to the house.

3.4 HOW TO SHUT DOWN THE SYSTEM FOR
LONG PERIODS

If the house is to be left unoccupied for any length of time –
especially during the winter – the system should be thoroughly
drained of all water. The gas, water, and electricity supply to
the house should also be turned off. For more detailed advice
contact your installer.

3.5 HOW TO CARE FOR THE APPLIANCE

FAULT CODES

ALARM CODE CAUSE ALARM TYPE ACTION

_St

AUTOSTOP Final Call engineer

_CL

CALL FOR SERVICE Temporary then fi nal Call engineer

A01

Ignition failure, fl ame not sensed,
internal fault

Final Reset, check appliance operation

A02

Limit thermostat fault Final Reset, check appliance operation

A03

Fan tacho signal fault Final Reset check appliance operation, check fan

A04

Insuffi cient system water pressure Final

Check/refi ll system pressure, reset, check
appliance operation

A06

DHW thermistor fault Temporary Check DHW thermistor

A07

Primary (fl ow) thermistor fault Temporary Check primary thermistor, check wiring

Primary (fl ow) thermistor over temperature

Temporary then fi nal Reset, check appliance operation

Temperature differential Final

Reset, check appliance operation, check
thermistors

A08

Return thermistor fault Temporary Check return thermistor, check wiring

Return thermistor over temperature Temporary then fi nal Reset, check appliance operation

Temperature differential inverted Final

Reset, check pump, ensure there is suf­fi cient circulation around heating circuit/s

A09

Flue thermistor or fl ue thermistor
counter fault

Temporary

Check fl ue thermistor counter at power
on, check fl ue thermistor, check wiring

Flue thermistor over temperature Final Reset, check appliance operation

A11

False fl ame Temporary None

A77

Low temperature thermostat fault Temporary Check low temperature thermostat

Adj

Calibration Na None

ACO

Service operation Na None







Purge cycle mode active Na None

P

Preheating function active Na None

P blinking

Preheating function running Na None

Flame ON Na None

Hours Stand-by Na None

- - OFF Na None

To clean the
outer cas­ing use only
a clean damp
cloth. Do not
use any scour­ers or abrasive
cleaners.

5

4.1 WHAT IF I SUSPECT A GAS LEAK

If you suspect a gas leak, turn off the gas supply at the gas
meter and contact your installer or local gas supplier. If you
require further advice please contact your nearest Vokèra offi ce.

4.2 WHAT IF I HAVE FREQUENTLY TO TOP-UP
THE SYSTEM

If the system regularly requires topping-up, it may be indicative
of a leak. Please contact your installer and ask him to inspect
the system.

4.3 WHAT IF THE APPLIANCE IS DUE ITS AN­NUAL SERVICE

Advice for tenants only

Your landlord should arrange for servicing.

5.1 - SETTING THE VOKÈRA MECHANICAL
CLOCK

If your boiler has been installed with the Vokèra mechanical
clock, it can be used and adjusted as follows:

Setting the time

The time of day can be set by grasping the outer edge of the
black dial and turning it in a clockwise direction until the correct
time is in line with the white pointer.

Setting the “switching times”

The “ON” periods are set by sliding the black tappets, adja-
cent to the time periods required, to the outer edge of the dial.
The tappets that remain at the centre of the dial will be the
“OFF” periods.
The smallest switching time (ON or OFF) is 15 minutes.
To select “AUTO” mode move the selector switch in central
position.
To select “ON” mode move the selector switch in the bottom
position.
To select “OFF” mode move the selector switch in the upper
position.

AUTO

ON

OFF

Fig. 4

4. WHAT IF...

5. SETTING THE VOKÈRA...

Advice for homeowners
Please contact Vokèra Customer Service (0844 3910999 (UK)
or 056 7755057 (ROI) if you would prefer a Vokèra service

engineer or agent to service your appliance. Alternatively your
local GAS SAFE registered engineer may be able to service
the appliance for you.

4.4 - WHAT IF I NEED TO CALL AN ENGINEER

If you think your boiler may have developed a fault, please contact
your installer or Vokèra Customer Services (0844 3910999 (UK)
or 056 7755057 (ROI) have all your details to hand including
full address and postcode, relevant contact numbers, and your
completed appliance log book.

6

All installers are asked to follow the Benchmark Scheme by
adhering to the Code of Practise, which can be obtained from
www.centralheating.co.uk.

The Compact A comprises a range of high-effi ciency combina-
tion boilers with outputs to DHW of 25kW and 30kW respec­tively. These appliances – by design – incorporate electronic
ignition, circulating pump, expansion vessel, safety valve, pres­sure gauge and automatic by-pass.
The Compact A range is produced as room sealed, category
II2H3P appliances, suitable for internal wall mounting applica­tions only. Each appliance is provided with a fan powered fl ue
outlet with an annular co-axial combustion air intake that can

be rotated – horizontally – through 360 degrees for various
horizontal or vertical applications. The Compact A can also be
used with the Vokèra twin fl ue system.
The Compact A is approved for use with C13 & C33 type fl ue
applications.
These appliances are designed for use with a sealed system
only; consequently they are not intended for use on open
vented systems.
This booklet is an integral part of the appliance. It is therefore
necessary to ensure that the booklet is handed to the person
responsible for the property in which the appliance is located/
installed. A replacement copy can be obtained from Vokèra
customer services.

Fig. 5

General layout

1 Domestic hot water heat exchanger
2 Drain valve
3 Three porte valve actuator
4 Safety valve
5 Pump
6 Bottom auto air vent (AAV)
7 Main heat exchanger
8 Flues thermistor (NTC)
9 Fan assembly with mixer
10 Silencer
11 Flue gas analysis test point
12 Flue outlet & air intake
13 Ignition transformer
14 Top AAV+De-aerator
15 Spark Electrode
16 Sensing Electrode
17 Flow thermistor (NTC) - High limit thermostat
18 Expansion vessel
19 Pressure switch
20 Return thermistor (NTC)
21 Gas valve
22 Domestic hot water sensor
23 Condense trap
24 DHW fl ow switch

R Heating return connection
F Heating fl ow connection
G Gas connection
O Hot water outlet
I Cold water inlet

INTRODUCTION

INSTALLATION AND SERVICING INSTRUCTIONS

R F G O I

7

1.1 PRINCIPLE COMPONENTS

• A fully integrated electronic control board featuring electronic
temperature control, anti-cycle control, pump over-run, self­diagnostic fault indicator, full air/gas modulation

• Aluminium heat exchanger

• Electronic ignition with fl ame supervision

• Integral high-head pump

• Fan

• Expansion vessel

• Water pressure switch

• Flue sensor

• Pressure gauge

• Safety valve

1.2 MODE OF OPERATION (at rest)

When the appliance is at rest and there are no requests for
heating or hot water, the following functions are active:

• frost-protection system – the frost-protection system protects
the appliance against the risk of frost damage both for CH
and DHW. For CH line, if the main temperature falls to 5°C,
the appliance will function on minimum power until the tem­perature on main reaches 35°C.

Moreover if the DHW temperature falls to 5°C, the appliance

will function on minimum power until the temperature on main
reaches 55°C.

• anti-block function – the anti-block function enables the pump
and divertor valve actuator to be energised for short periods,
when the appliance has been inactive for more than 24-hours.

1.3 MODE OF OPERATION (Heating)

When there is a request for heat via the time clock and/or any
external control, the pump and fan are started, the fan speed
will modulate until the correct signal voltage is received at the
control PCB. At this point an ignition sequence is enabled.
Ignition is sensed by the electronic circuit to ensure fl ame stability
at the burner. Once successful ignition has been achieved, the
electronic circuitry increases the gas rate to 75% for a period of
15 minutes. Thereafter, the boiler’s output will either be increase
to maximum or modulate to suit the set requirement. When
the appliance reaches the desired temperature the burner will
shut down and the boiler will perform a three-minute anti-cycle
(timer delay).
When the request for heat has been satisfi ed the appliance
pump and fan may continue to operate to dissipate any residual
heat within the appliance.

1.4 MODE OF OPERATION (Hot water)

When there is a request for DHW via a hot water outlet or tap,
the pump and fan are started, the fan speed will modulate until
the correct signal voltage is received at the control PCB. At this
point an ignition sequence is enabled.
Ignition is sensed by the electronic circuit to ensure fl ame stabil-
ity at the burner. Once successful ignition has been achieved,
the electronic circuitry increases the gas rate to maximum or
will modulate output to stabilise the temperature.
In the event of the appliance exceeding the desired temperature
(set point) the burner will shut down until the temperature drops.
When the request for DHW has been satisfi ed the appliance
pump and fan may continue to operate to dissipate any residual
heat within the appliance.

Fig. 6

Expansion

vessel

Safety

valve

Pump

Return

temperature

sensor

Main heat

exchanger

Bottom

AAV

Pressure

switch

DHW heat
exchanger

Diverter

valve

Drain
valve

DHW tem-

perature

sensor

Flow temperature

sensor

Top AAV

Automatic

by-pass

DHW

non return

valve

CH

return

CH

fl ow

DHW

inlet

DHW

outlet

Flow regu-

lator

DHW fl ow

switch

SECTION 1 - DESIGN PRINCIPLES AND OPERATING SEQUENCE

1.5 SAFETY DEVICES

When the appliance is in use, safe operation is ensured by:

• a water pressure switch that monitors system water pressure

and will de-activate the pump, fan, and burner should the
system water pressure drop below the rated tolerance;

• fan speed sensor to ensure safe operation of the burner;

• a high limit thermostat that over-rides the temperature control

circuit to prevent or interrupt the operation of the burner;

• fl ame sensor that will shut down the burner when no fl ame

signal is detected;

• fl ue sensor;

• a safety valve which releases excess pressure from the

primary circuit.

8

SECTION 2 - TECHNICAL DATA

2.1 Central Heating Compact A 25 Compact A 29

Heat input (kW) 20.00 25.00

Maximum heat output (kW) 60/80°C 19.50 24.45

Minimum heat output (kW) 60/80°C 4.91 5.90

Maximum heat output (kW) 30/50°C 20.84 26.23

Minimum heat output (kW) 30/50°C 5.36 6.40

Minimum working pressure 0.25-0.45 bar

Maximum working pressure 2.5 bar

Minimum fl ow rate 350 l/h

2.2 Domestic Hot Water Compact A 25 Compact A 29

Heat input (kW) 25.00 29.00

Flow Rate: ΔT35°C 10.20 11.9

Maximum inlet pressure 6 bar

Minimum inlet pressure 0.15 bar

Minimum fl ow rate 2 l/min

2.3 Gas Pressures Compact A 25 Compact A 29

Inlet pressure (G20) 20.0 mbar 20.0 mbar

Heating maximum gas rate (m3/hr) 2.12 2.64

DHW maximum gas rate (m3/hr) 2.64 3.07

Minimum gas rate (m3/hr) 0.53 0.63

Injector size (mm) 5.1 5.6

Silencer fl ange (ø mm) (fi tted) 31 -

2.4 Expansion Vessel Compact A 25 Compact A 29

Capacity 8 litres

Maximum system volume 74 litres

Pre-charge pressure 1 bar

2.5 Dimensions Compact A 25 Compact A 29

Height (mm) 715

Width (mm) 405

Depth (mm) 250

Dry weight (kg) 26 27

2.6 Clearances Compact A 25 Compact A 29

Sides 12mm

Top 150mm from casing or 25mm above fl ue elbow (whichever is applicable)

Bottom 150mm

Front 600mm

2.7 Connections Compact A 25 Compact A 29

Flow & return 22mm

Gas 15mm

DHW hot & cold 15mm

Safety valve 15mm

Condense

21mm

2.8 Electrical Compact A 25 Compact A 29

Power consumption (Watts) 110 119

Voltage (V/Hz) 230/50

Internal fuse 3.15A T (for PCB) - 3.15A F (for connections block)

External fuse 3A

2.9 Flue Details (concentric 60-100) Compact A 25 Compact A 29

Maximum horizontal fl ue length (60/100mm) 5.85m 4.85m

Maximum vertical fl ue length (60/100mm) 6.85m 5.85m

2.9A Flue Details (concentric 80-125) Compact A 25 Compact A 29

Maximum horizontal fl ue length (80/125mm) 15.3m 12.8m

Maximum vertical fl ue length (80/125mm) 20.3m 17.8m

2.9B Flue Details (twin pipes) Compact A 25 Compact A 29

Maximum horizontal fl ue length (80mm/80mm) 45m/45m 40m/40m

Maximum vertical fl ue length (80mm/80mm) 45m/45m 40m/40m

9

Fig. 7

2.12 PUMP DUTY

Fig. 6 shows the fl ow-rate available – after
allowing for pressure loss through the ap­pliance – for system requirements. When
using this graph, apply only the pressure
loss of the system. The graph is based on
a 20

o

C temperature differential.

Fig. 8

Flow rate (l/h)

Residual head (x 100 mbar)

1st speed

2nd speed

3rd speed

0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

4,0

4,5

5,0

0 100 200 300 400 500 600 700 800 900 1000

2.10 Effi ciency Compact A 25 Compact A 29

SEDBUK (%) 90.0 90.2

2.11 Emissions Compact A 25 Compact A 29

CO2 @ maximum output (%) 9.0 9.0

CO2 @ minimum output (%) 9.5 9.5

CO @ maximum output (ppm) 180 160

CO @ minimum output (ppm) 20 20

NOx rating class 5 class 5

Key Location Minimum distance

A Below an opening (window, air-brick, etc.) 300 mm
B Above an opening (window, air-brick, etc.) 300 mm
C To the side of an opening (window, air-brick, etc.) 300 mm
D Below gutter, drain-pipe, etc. 25 mm
E Below eaves 25 mm
F Below balcony, car-port roof, etc. 25 mm
G To the side of a soil/drain-pipe, etc. 25 mm (60mm for 80/125 - 5” fl ue)
H From internal/external corner 25 mm (60mm for 80/125 - 5” fl ue)
I Above ground, roof, or balcony level 300 mm
J From a surface or boundary facing the terminal 600 mm
K From a terminal facing a terminal 1200 mm
L From an opening in the car-port into the building 1200 mm
M Vertically from a terminal on the same wall 1500 mm
N Horizontally from a terminal on the same wall 300 mm
P From a structure to the side of the vertical terminal 300 mm
Q From the top of the vertical terminal to the roof fl ashing As determined by the fi xed collar
of the vertical terminal
R To the side of a boundary 300 mm
S To the side of an opening or window on a pitched roof 600 mm
T Below an opening or window on a pitched roof 2000 mm
V From a vertical terminal to an adjacent opening (window, air-brick, etc.) (call Vokera technical for advice)
W From a vertical terminal to an adjacent vertical terminal 300 mm (only if both terminals are the same hight)

10

SECTION 3 - GENERAL REQUIREMENTS (UK)

This appliance must be installed by a competent person in ac­cordance with the Gas Safety (Installation & Use) Regulations.

3.1 RELATED DOCUMENTS

The installation of this boiler must be in accordance with the
relevant requirements of the Gas Safety (Installation & Use)
Regulations, the local building regulations, the current I.E.E.
wiring regulations, the bylaws of the local water undertaking,
the Building Standards (Scotland) Regulation and Building
Standards (Northern Ireland) Regulations.
It should be in accordance also with any relevant requirements
of the local authority and the relevant recommendations of the
following British Standard Codes of Practice.

3.2 LOCATION OF APPLIANCE

The appliance may be installed in any room or internal space,
although particular attention is drawn to the requirements
of the current I.E.E. wiring regulations, and in Scotland, the
electrical provisions of the Building Regulations, with respect
to the installation of the appliance in a room or internal space

BS 5440 PART 1 FLUES
BS 5440 PART 2 FLUES & VENTILATION

BS 5449 PART 1 FORCED CIRCULATION HOT WATER SYSTEMS
BS 5546 INSTALLATION OF GAS HOT WATER SUPPLIES FOR DOMESTIC PURPOSES
BS 6798 INSTALLATION OF BOILERS OF RATED INPUT NOT EXCEEDING 60kW
BS 6891 LOW PRESSURE INSTALLATION PIPES
BS 7074 PART 1 APPLICATION, SELECTION, AND INSTALLTION OF EXPANSION VESSELS
AND ANCILLARY EQUIPMENT FOR SEALED WATER SYSTEMS

BS 5440 Part 1, when the terminal is 0.5 metres (or less) below
plastic guttering or 1 metre (or less) below painted eaves.

3.5 AIR SUPPLY

The following notes are intended for general guidance only.
This appliance is a room-sealed, fan-fl ued boiler, consequently
it does not require a permanent air vent for combustion air sup­ply. When installed in a cupboard or compartment, ventilation
for cooling purposes is also not required.

3.6 WATER CIRCULATION

Detailed recommendations are given in BS 5449 Part 1 and
BS 6798. The following notes are for general guidance only.

3.6.1 PIPEWORK

It is recommended that copper tubing to BS 2871 Part 1 is used
in conjunction with soldered capillary joints. Where possible
pipes should have a gradient to ensure air is carried naturally to
air release points and that water fl ows naturally to drain cocks.

Except where providing useful heat, pipes should be insulated
to avoid heat loss and in particular to avoid the possibility of
freezing. Particular attention should be paid to pipes passing
through ventilated areas such as under fl oors, loft space and
void areas.

3.6.2 AUTOMATIC BY-PASS

The appliance has a built-in automatic by-pass, consequently
there is no requirement for an external by-pass, however the
design of the system should be such that it prevents boiler
‘cycling’.

3.6.3 DRAIN COCKS

These must be located in accessible positions to facilitate
draining of the appliance and all water pipes connected to the
appliance. The drain cocks must be manufactured in accord­ance with BS 2879.

3.6.4 AIR RELEASE POINTS

These must be positioned at the highest points in the system
where air is likely to be trapped. They should be used to expel
trapped air and allow complete fi lling of the system.

3.6.5 EXPANSION VESSEL

The appliance has an integral expansion vessel to accom­modate the increased volume of water when the system is
heated. It can accept up to 8 litres of expansion from within
the system, generally this is suffi cient, however if the system
has an unusually high water content, it may be necessary to
provide additional expansion capacity (see 6.18).

3.6.6 FILLING POINT

A method for initial fi lling of the system and replacing water lost
during servicing etc. directly from the mains supply, is provided
(see fi g. 9). This method of fi lling complies with the current Water
Supply (Water Fittings) Regulations 1999 and Water Bylaws
2000 (Scotland). If an alternative location is preferred, it should
be connected as detailed in fi g. 9.

3.6.7 LOW PRESSURE SEALED SYSTEM

An alternative method of fi lling the system would be from an
independent make-up vessel or tank mounted in a position at
least 1 metre above the highest point in the system and at least
5 metres above the boiler (see fi g. 10).
The cold feed from the make-up vessel or tank must be fi tted
with an approved non-return valve and stopcock for isolation

containing a bath or shower.
When an appliance is installed in a room or internal space
containing a bath or shower, the appliance or any control per­taining to it must not be within reach of a person using the bath
or shower. The location chosen for the appliance must permit
the provision of a safe and satisfactory fl ue and termination.
The location must also permit an adequate air supply for com­bustion purposes and an adequate space for servicing and air
circulation around the appliance. Where the installation of the
appliance will be in an unusual location special procedures may
be necessary, BS 6798 gives detailed guidance on this aspect.
A compartment used to enclose the appliance must be designed
and constructed specifi cally for this purpose. An existing com-
partment/cupboard may be utilised provided that it is modifi ed
to suit. Details of essential features of compartment/cupboard
design including airing cupboard installations are given in BS

6798. This appliance is not suitable for external installation.

3.3 GAS SUPPLY

The gas meter – as supplied by the gas supplier – must be
checked to ensure that it is of adequate size to deal with the
maximum rated input of all the appliances that it serves. Instal­lation pipes must be fi tted in accordance with BS 6891.
Pipe work from the meter to the appliance must be of adequate
size. Pipes of a smaller size than the appliance gas inlet con­nection must not be used. The installation must be tested for
tightness in accordance with BS6891.
If the gas supply serves more than one appliance, it must be
ensured that an adequate supply is maintained to each appli­ance when they are in use at the same time.

3.4 FLUE SYSTEM

The terminal should be located where the dispersal of combustion
products is not impeded and with due regard for the damage
and discoloration that may occur to building products located
nearby. The terminal must not be located in a place where it
is likely to cause a nuisance (see fi g. 8). In cold and/or humid
weather, water vapour will condense on leaving the terminal;
the effect of such pluming must be considered.
If installed less than 2m above a pavement or platform to which
people have access (including balconies or fl at roofs) the terminal
must be protected by a guard of durable material.
The guard must be fi tted centrally over the terminal. Refer to