VOKERA Compact 25, Compact 29 User Instructions

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 efficiency combi boiler

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 3

3.2 How to reset the appliance 3

3.3 How to shut down the system for short periods 3

3.4 How to shut down the system for long periods 3

3.5 How to care for the appliance 3

What if... Page

4.1 What if I suspect a gas leak 4

4.2 What if I have frequently top-up the system 4

4.3 What if the appliance is due its annual service 4

4.4 What if I need to call an engineer 4

Setting the Vokèra Page

5.1 Setting the Vokèra mechanical clock 4

Installation and Servicing instructions

Design principles & operating sequence Page

1.1 Principle components 6

1.2 Mode of operation (at rest) 6

1.3 Mode of operation (heating) 6

1.4 Mode of operation (Hot water) 6

1.5 Safety devices 6

Technical data Page

2.1 Central heating 7

2.2 Domestic hot water 7

2.3 Gas pressures 7

2.4 Expansion vessel 7

2.5 Dimensions 7

2.6 Clearances 7

2.7 Connections 7

2.8 Electrical 7

2.9 Flue details (concentric) 7

2.9A Flue details (twin pipes) 7

2.9B Flue details (80/125) 7

2.10 Efficiency 7

2.11 Emissions 7

2.12 Pump duty 8

General requirements (UK) Page

3.1 Related documents 9

3.2 Location of appliance 9

3.3 Gas supply 9

3.4 Flue system 9

3.5 Air supply 9

3.6 Water circulation 9

3.7 Electrical supply 10

3.8 Mounting on a combustible surface 10

3.9 Timber framed buildings 10

3.10 Inhibitors 10

3.11 Showers 10

General requirements (EIRE) Page

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

Installation Page

4.1 Delivery 12

4.2 Contents 12

4.3 Unpacking 12

4.4 Preparation for mounting the appliance 12

4.5 Fitting the flue 12

4.6 Connecting the gas & water 15

4.7 Electrical connections 16

Commissioning Page

5.1 Gas supply installation 17

5.2 The heating system 17

5.3 Initial filling of the system 17

5.4 Initial flushing of the system 17

5.5 Pre-operation checks 17

5.6 Initial lighting 17

5.7 Checking gas pressure & combustion analysis 17

5.8 Final flushing of the heating system 17

5.9 Setting the boiler operating temperature 17

5.10 Setting the system design pressure 17

5.11 Regulating the central heating system 18

5.12 Final checks 18

5.13 Instructing the user 18

Servicing Page

6.1 General 18

6.2 Routine annual servicing 18

6.3 Replacement of components 18

6.4 Component removal procedure 18

6.5 Pump assembly 19

6.6 Safety valve 19

6.7 Lower automatic air release valves 19

6.8 Water pressure switch 19

6.9 Flow thermistor 19

6.10 Return thermistor 19

6.11 Printed circuit board 19

6.12 Gas valve 20

6.13 Electrodes 20

6.14 Flue fan & mixer 20

6.15 Burner 20

6.16 Main heat exchanger 21

6.17 Automatic by-pass & DHW non-return valve 21

6.18 Expansion vessel removal 21

6.19 Condense trap removal 21

6.20 Flue collector removal 22

Checks, adjustments and fault finding Page

7.1 Checking appliance operation 23

7.2 Appliance modes of operation 23

7.3 Checking the CO2 & adjusting the valve 23

7.4 Combustion analysis test 24

7.5 Checking the expansion vessel 24

7.6 External faults 24

7.7 Electrical checks 24

7.8 Fault finding 25

7.9 Component values & characteristics 25

Wiring diagrams Page

8.1 External wiring 26

8.2 Typical control applications 26

8.3 Other devices 26

8.4 Vokèra twin-channel programmer 26

Exploded diagrams Page

9.1 Table 1 28

9.2 Table 2 29

9.3 Table 3 30

9.4 Table 4 31

9.5 Table 5 32

L.P.G. instructions Page

10.1 Related documents 33

10.2 Technical data 33

10.3 Converting the appliance gas type 33

10.4 Gas supply 33

10.5 Gas supply installation 33

10.6 Checking the CO2 and adjusting the gas valve 33

Benchmark 35-36

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 fitted.

Warning: this appliance must be earthed!

1.3 GUARANTEE REGISTRATION CARD

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

1.4 APPLIANCE LOG BOOK (UK only)

A logbook 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 logbook 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 may
invalidate the warranty. This does not affect your statutory
rights.

1.5 HOW DOES IT WORK?

Your Compact 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 fitted. 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 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 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 efficiency.
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 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

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

Compact 25-29

HEIGHT 715 mm
WIDTH 405 mm
DEPTH 248 mm

1.8 FROST PROTECTION SYSTEM

The Compact 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
appliance.
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 3 status LED indicators, the Green
LED indicates that the flame is present, the Red LED indicates
the appliance has detected a fault, whilst the Yellow LED
indicates that there is Servicing operation in progress.

1. THINGS YOU SHOULD KNOW

2

Fig. 1

BOILER STATUS LED

Green LED Boiler is working/responding to a heating/hot water request
Red LED Boiler has identified a fault and has failed-safe. Refer to instructions on how to reset
Yellow LED Service operation

DHW 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:

MODE

SELECTOR

SWITCH

RED LED

GREEN LED

HEATING

TEMPERATURE

SELECTOR

HYDROMETRE

DHW

TEMPERATURE

SELECTOR

YELLOW LED

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 heating outlet temperature, or
counter-clockwise to reduce the temperature (range:
37°C-60°C)

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

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 position 4 and 6.

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 efficient operation of the
appliance is 0.5 BAR. Should the pressure fall below 0.5
BAR, the boiler may lockout.

correct

pressure

value

3

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 fitted);

- any external thermostats and their functions;

- the appliance controls.

2.2 APPLIANCE CONTROLS (see fig. 1)

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

- pressure gauge;

- appliance mode selector;

- temperature selector;

- burner ON mode (green);

- fault indicator (red);

- servicing mode indicator (yellow)

- optional integral time clock/programmer (if fitted).

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 flows from your hot water taps. The temperature range is
adjustable between 40

o

C and 80oC for the central heating, and

between 37oC and 60oC for the hot water.
The 3 LED normally shows the operating temperature of the
appliance.
When the status indicator (Green) is lit it indicates that the
flame is present and the burner is ON.
When the fault indicator (Red) is lit it indicates that the
appliance has identified a possible fault and performed a safety
lockout.
When the fault indicator (Yellow) is lit it indicates that there is
a Servicing operation in progress.
The integral time clock (when fitted) can be 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 satisfied, the appliance will switch
off automatically.

2.4 ADJUSTING THE HEATING 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 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
sufficiently hot enough, it may be necessary to reduce the flow
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 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
4 and 6 sector) to automatically adjust (raise) the heating.
The activation and the disable of the function is visualized by
blinking the green led.

2. GETTING STARTED

3.1 HOW TO TOP-UP THE SYSTEM PRESSURE
(fig. 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 filling valve connections (usually beneath the
boiler, see fig. 2).

- Attach the filling loop to both connections.

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

- Close the filling valve when the pressure gauge (on the
boiler) reads between 1 and 1.5 BAR (see fig. 1).

- Remove the filling loop from the connections.

3.2 HOW TO RESET THE APPLIANCE

When the red fault LED is illuminated, 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 fig. 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. 2

control

valve

temporary

connection

control

valve

supply pipe

double

check valve

flow/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

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

4

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 office.

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, adja­cent 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.

APPLIANCE STATUS LED AND FAULT CODES

Alarm type Led RED Led YELLOW Led GREEN Action

Purge cycle mode active NA BLINKING BLINKING BLINKING

Alarm high limit thermostat Final BLINKING OFF OFF Reset appliance. Call

engineer if fault re-occurs

Alarm system water pressure Final ON OFF ON Check/refill system pressure,

reset, check.
Call engineer if fault re-occurs

Alarm safety shutdown and/or Final ON OFF OFF Reset appliance. Call
internal fault engineer if fault re-occurs

Temporary fault Temporary OFF OFF BLINKING None

Service operation NA OFF BLINKING OFF None

Flame ON NA OFF OFF ON None

Fault sensors Final BLINKING OFF BLINKING Reset appliance. Call

engineer if fault re-occurs

Boiler stand-by NA OFF OFF BLINKING None

AUTO

ON

OFF

Fig. 3

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.

5

The Compact comprises a range of high-efficiency
combination 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 range is produced as room sealed, category
II2H3P appliances, suitable for internal wall mounting
applications only. Each appliance is provided with a fan
powered flue 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 can

also be used with the Vokèra twin flue system.
The Compact is approved for use with C13 & C33 type flue
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. 4

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 Top AAV
14 De-aerator
15 Spark Electrode - Sensing Electrode
16 Ignition transformer
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 flow switch

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

INTRODUCTION

INSTALLATION AND SERVICING INSTRUCTIONS

R F G O I

6

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 flame 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 flame
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 satisfied 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 flame
stability 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
satisfied the appliance pump and fan may continue to operate
to dissipate any residual heat within the appliance.

Fig. 5

Expansion

vessel

Safety

valve

Pump

Return

temperature

sensor

Main heat

exchanger

Bottom

AAV

Pressure

switch

DHW heat
exchanger

Diverter

valve

Drain
valve

DHW

temperature

sensor

Flow temperature

sensor

Top AAV

Automatic

by-pass

DHW

non return

valve

CH

return

CH

flow

DHW

inlet

DHW
outlet

Flow

regulator

DHW flow

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;

• flame sensor that will shut down the burner when no flame
signal is detected;

• flue sensor;

• a safety valve which releases excess pressure from the

primary circuit.

7

2.1 Central Heating Compact 25 Compact 29

Heat input (kW) 20.00 25
Maximum heat output (kW) 60/80°C 19.50 24.40
Minimum working pressure 0.5 bar
Maximum working pressure 2.7 bar
Minimum flow rate 350 l/h

2.2 Domestic Hot Water Compact 25 Compact 29

Heat input (kW) 25.00 29.50
Flow Rate: ΔT35oC 10.2 l/min 12.1 l/min
Maximum inlet pressure 6 bar
Minimum inlet pressure 0.15 bar
Minimum flow rate 2 l/min

2.3 Gas Pressures Compact 25 Compact 29

Inlet pressure (G20) 20.0 mbar
Heating maximum gas rate (m3/hr) 2.12 2.64
DHW maximum gas rate (m3/hr) 2.64 3.12
Minimum gas rate (m3/hr) 0.53 0.63
Injector size (mm) 4.8 5.7
Silencer flange (ø mm) (fitted) 27 31

2.4 Expansion Vessel Compact 25 Compact 29

Capacity 8 litres
Maximum system volume 74 litres
Pre-charge pressure 1 bar

2.5 Dimensions Compact 25 Compact 29

Height (mm) 715
Width (mm) 405
Depth (mm) 248
Dry weight (kg) 30 32

2.6 Clearances COMPACT Range

Sides 12mm
Top 150mm from casing or 25mm above flue elbow (whichever is applicable)
Bottom 150mm
Front 500mm

2.7 Connections COMPACT Range

Flow & return 22mm
Gas 22mm
DHW hot & cold 15mm
Safety valve 15mm
Condense 21mm

2.8 Electrical Compact 25 Compact 29

Power consumption (Watts) 123W 140W
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) Compact 25 Compact 29

Maximum horizontal flue length (60/100mm) 4.0m
Maximum vertical flue length (60/100mm) 5.0m

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

Maximum horizontal flue length (80mm/80mm) 20m/20m
Maximum vertical flue length (80mm/80mm) 20m/20m

2.10 Efficiency Compact 25 Compact 29
SEDBUK (%) 90.0 90.1

2.11 Emissions Compact 25 Compact 29

CO2 @ maximum output (%) 9.0 9.0
CO2 @ minimum output (%) 9.5 9.5
CO @ maximum output (ppm) 200 160
CO @ minimum output (ppm) 30 35
NOx rating class 5 class 5

SECTION 2 - TECHNICAL DATA

8

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” flue)
H From internal/external corner 25 mm (60mm for 80/125 - 5” flue)

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 flashing As determined by the fixed 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)

Fig. 6

2.12 PUMP DUTY

Fig. 6 shows the flow-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. 7

Flow rate (l/h)

Residual head (x 100 mbar)

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 1100

1st speed

2nd speed

3rd speed

9

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
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 flue 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 specifically for
this purpose. An existing compartment/cupboard may be utilised
provided that it is modified 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 fitted 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 fig. 7). 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

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

people have access (including balconies or flat roofs) the
terminal must be protected by a guard of durable material.
The guard must be fitted centrally over the terminal. Refer to 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-flued 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 flows 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 floors,
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 filling 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 sufficient, 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 filling of the system and replacing water lost
during servicing etc. directly from the mains supply, is provided
(see fig. 8). This method of filling 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 fig. 8.

3.6.7 LOW PRESSURE SEALED SYSTEM

An alternative method of filling 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 fig. 9).
The cold feed from the make-up vessel or tank must be fitted

10

This appliance must be installed by a competent person in
accordance with and defined by, the Standard Specification
(Domestic Gas Installations) Declaration (I.S. 813).

3A.1 RELATED DOCUMENTS

The installation of this boiler must be in accordance with the
relevant requirements of the local building regulations, the
current ETCI National Rules for Electrical Installations and the
bylaws of the local water undertaking.
It should be in accordance also with any relevant requirements
of the local and/or district authority.

3A.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 ETCI National Rules for Electrical Installations,
and I.S. 813, Annex K.
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 flue 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, refer to I.S. 813 for detailed guidance on this aspect.
A compartment used to enclose the appliance must be designed

SECTION 3A - GENERAL REQUIREMENTS (EIRE)

with an approved non-return valve and stopcock for isolation
purposes. The feed pipe should be connected to the return
pipe as close to the boiler as possible.

3.6.8 FREQUENT FILLING

Frequent filling or venting of the system may be indicative of a
leak. Care should be taken during the installation of the
appliance to ensure all aspects of the system are capable of
withstanding pressures up to at least 3 bar.

3.7 ELECTRICAL SUPPLY

The appliance is supplied for operation on 230V @ 50Hz
electrical supply; it must be protected with a 3-amp fuse. The
method of connection to the mains electricity supply must allow
for complete isolation from the supply. The preferred method
is by using a double-pole switch with a contact separation of at
least 3,5mm (3° high-voltage category). The switch must only
supply the appliance and its corresponding controls, i.e. time
clock, room thermostat, etc. Alternatively an un-switched
shuttered socket with a fused 3-pin plug both complying with
BS 1363 is acceptable.

3.8 MOUNTING ON A COMBUSTIBLE SURFACE

If the appliance is to be fitted on a wall of combustible material,
a sheet of fireproof material must protect the wall.

3.9 TIMBER FRAMED BUILDINGS

If the appliance is to be fitted in a timber framed building, it
should be fitted in accordance with the Institute of Gas Engineers
publication (IGE/UP/7) ‘Guide for Gas Installations in Timber
Frame Buildings’.

3.10 INHIBITORS

Vokèra recommend that an inhibitor - suitable for use with
aluminium heat exchangers - is used to protect the boiler and
system from the effects of corrosion and/or electrolytic action.
The inhibitor must be administered in strict accordance with
the manufacturers instructions*.
*Water treatment of the complete heating system - including the
boiler - should be carried out in accordance with BS 7593 and
the Domestic Water Treatment Association’s (DWTA) code of
practice.

flow/return

pipe

control

valve

temporary

connection

control

valve

supply

pipe

double

check valve

Fig. 8

Fig. 9

Make-up vessel
or tank

Automatic
air-vent

Non-return

valve

Stopcock

5.0 metres minimum

Heating
return

3.11 SHOWERS

If the appliance is intended for use with a shower, the shower
must be thermostatically controlled and be suitable for use
with a combination boiler.

and constructed specifically for this purpose. An existing
compartment/cupboard may be utilised provided that it is
modified to suit.
This appliance is not suitable for external installation.

3A.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 fitted in accordance with I.S. 813.
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 I.S. 813.
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.

3A.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 I.S. 813).
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 flat roofs) the