Trianco AZTEC 6 User guide

AZTEC 6, 9 & 12kW
WALL HUNG
MAXI COMBINATION
BOILER
INSTALLATION, OPERATION AND
SERVICING INSTRUCTIONS
Please read these instructions carefully before installing
and operating this appliance
TO BE RETAINED BY THE HOUSEHOLDER

2
CONTENTS PAGE
HEALTH AND SAFETY 3
PRE-INSTALLATION NOTES 4
AFTER SALES SERVICE 5
INTRODUCTION 6
IMPORTANT SAFETY NOTES 6
USER INSTRUCTIONS 7
SIMPLE FAULT FINDING 8
TECHNICAL DETAILS 8
INSTALLATION 9
VENTILATION REQUIREMENTS 11
WATER SYSTEM 11 - 12
SEALED WATER SYSTEM REQUIREMENTS 12 - 14
WIRING INSTRUCTIONS 14
WIRING DIAGRAMS 15
SERVICING 16
PART REPLACEMENT 16 - 17
FAULT FINDING 17 - 18
FAULT FINDING FLOW CHARTS 19 - 22
SPARES/EXPLODED VIEW 23 - 25

3
HEALTH AND SAFETY
INFORMATION FOR THE USER, INSTALLER AND SERVICE ENGINEER
Under the Consumer Protection Act 1987 and the Health and Safety at Work Act 1974, it is a requirement to provide
information on substances hazardous to health (COSHH Regulations 1998).
TR Engineering takes every reasonable care to ensure that its products are designed and constructed to meet these safety
requirements when the products are properly installed and used. To fulfil the requirements, products are comprehensively
tested and examined before despatch.
When working on the appliance, it is the responsibility of the user or engineer to ensure that personal protective clothing or
equipment appropriate to parts that could be considered hazardous or harmful is worn.
This appliance may contain some of the items below:
Insulation and Seals
Glass rope, mineral wool, insulation pads, ceramic fibre and glass insulation.
When handling, avoid inhalation and contact with eyes. These may be harmful and cause irritation to the skin, eyes, nose or
throat. Use disposable gloves, facemasks and eye protection.
After handling, wash hands and other exposed areas. When disposing of materials, limit dust and the risk of inhalation by
using water spray. Ensure materials are securely wrapped.
Seek urgent medical attention if inhaled or ingested. Exposure to eyes and skin should be followed by immediate cleansing of
the affected areas and medical attention if necessary.
Glues, Sealants and Paints
The glues, sealants and paints used present no known hazards when the appliance is used in the manner for which it is
intended.
Notes:
a) Electrical safety checks should be carried out by a competent person.
b) It is a requirement of the guarantee and any extended warranty that an annual service is carried out by a competent
person.
Installation Engineers Signature
Company Name (if applicable)
Company Address
Company Tel. No.
Please read these instructions fully before installing this appliance.
If in doubt seek expert advice

4
These instructions should be kept in a place close to the appliance for easy reference.
IMPORTANT PRE-INSTALLATION NOTES
Before installation, it is imperative that the following guidelines are heeded to ensure the trouble-free and efficient
operation of the boiler:
Ventilation and Siting
When siting the boiler in a confined space it is essential that adequate ventilation be provided. This will ensure that air is
allowed to circulate freely around the appliance keeping down the ambient temperatures. Refer to Ventilation requirements
(Page 10) for further details.
Ensure that the area surrounding the boiler is kept free of items which would impede the good ventilation of the appliance
(eg. towels, linen, etc).
When siting the boiler, take into account the potential requirement for future servicing. Enough space should be provided at
the front of the boiler to enable an engineer to adequately service and/or replace items such as the PCB or heat exchanger.
Space should also be available for the removal of the front casing panel. Please refer to siting information (Page 9) for
clearance dimensions.
Power Supply and Wiring
The power supply to the premises must meet the minimum requirements of the unit being installed, with special attention
paid to the supply current, cable size, and RCD recommendation. The supply voltage to the appliance must never drop below
207 Volts.
When fitting external controls, such as a room thermostat or programmer, particular consideration should be given to the
wiring of these secondary items into the appliance. Please refer to the wiring instructions (Pages 13) for full details. Any
breakdown attended to by TR Engineering Ltd which is found to be caused by an incorrectly wired appliance will be
chargeable.
System
Isolation valves must be fitted on both the flow and return pipe work. These are useful as from time to time the boiler may
require draining of water, and the lengthy drawing-off process can be avoided by the astute placement of these valves.
Ensure that any isolation valves are open before first use, and that the system is full of water.
The boiler can only be fitted in an upright position.
IMPORTANT:
General Information:
To keep your boiler running efficiently DO NOT OBSTRUCT OR COVER any ventilation air inlet on the appliance or the
compartment where it is installed.
To keep the casing clean, switch ‘OFF’ the boiler at the electrical supply, and simply wipe with a damp cloth. DO NOT use
abrasive cleaning fluids as this may damage the stove enamel paintwork.
Important
The electrical supply requirements: -
The 6 kW boilers meet the requirements of EN 61000-3.3.
The 9-kW boiler must be installed in premises having a service supply of > 100A per phase.
The 12-kW boiler must be installed in premises having a system impedance of not more than 0.1939 + 0.1939Ω.

5
TR ENGINEERING LTD CUSTOMER AFTER SALES SERVICE INFORMATION
A step by step guide to reporting a fault with your
appliance
A qualified field SERVICE ENGINEER is available to attend a
breakdown or manufacturing fault occurring whilst the
appliance is under warranty.
The appliance must be made available for service during
normal working hours, Monday to Friday (no weekend
work or bank holidays accepted).
A charge will be made where:
 Our Field Service Engineer finds no fault with the
appliance or
 The cause of a breakdown is due to other parts of
the plumbing/heating system or with equipment
not supplied by TR Engineering Ltd. or
 Where the appliance falls outside the warranty
period (see terms and conditions enclosed). or
 The appliance has not been correctly installed, as
recommended (see installation, operating and
servicing instructions.)
NOTE: Over 50% of all service calls made are found to
have no appliance fault.
Register your boiler online
www.trianco.co.uk/product-registration
What to do in the event of an appliance fault or
breakdown:
Step 1: Always contact your installer in the first
instance, who must thoroughly check all his work
PRIOR to requesting a service visit from TR Engineering
LTD.
Step 2: If your appliance has developed an in-warranty
fault your installer should contact TR Engineering LTD
for assistance from site.
What happens if my Installer/engineer is
unavailable?
Step 3: Contact TR Engineering LTD. We will provide you
with the name and telephone number of our Service
Agent. However, a charge may apply if the fault is not
covered by the appliance warranty (payment will be
requested on site by our independent Service Agent).
PLEASE NOTE: UNAUTHORISED INVOICES FOR
ATTENDANCE AND REPAIR WORK CARRIED OUT ON THIS
APPLIANCE BY ANY THIRD PARTY WILL NOT BE ACCEPTED
BY TR ENGINEERING LTD.
SERVICE CENTRE AND TECHNICAL SUPPORT
Tel: [phone] Fax: [phone]
Hours of Business
Monday to Thursday 8.30am - 5pm
Friday 8.30am - 2.30pm

6
INTRODUCTION
The Aztec Electric Combination Boiler is a wall mounted
electric central heating boiler designed with smaller
properties in mind. Access is required to the front and the
top of the boiler for servicing. Once the boiler is switched
on it is fully controlled by an automatic management
system which monitors the safety and running functions of
the boiler. Designed to work on a fully pumped wet system
only. The boiler produces hot water by passing water over
electric heating elements housed in an insulated heat
exchanger.
IMPORTANT SAFETY NOTES
Read these instructions before installing your boiler.
The heating system must comply with the latest editions of
British Standards 5449 and The Building Regulations, and
Electrical Wiring Regulations BS 7671.
1. Always switch OFF the electrical supply before
removing the cover.
2. If any part of the boiler is modified, then the
warranty will be invalidated.
We recommend that you keep these instructions
in a place near your appliance for easy reference.
The Trianco Aztec Combination Wall Mounted Boiler has been designed to conform to
European Directive/Standards EN60335-1:2002 +A15:2011, EN60335-2-35:2002 inc Amd 1,
EN55014-1:2006 +A1:2009, EN55014-2:1997 +A2:2008.
THE PERSON(S) WHO INSTALLS THIS APPLIANCE, SERVICES OR CARRIES OUT ANY REMEDIAL WORK,
I.E. ELECTRICAL FAULT FINDING, MUST HAVE SUITABLE ENGINEERING QUALIFICATIONS.
WARNING: DO NOT SWITCH ON THIS APPLIANCE IF THERE IS ANY POSSIBILITY THAT THE WATER MAY
BE FROZEN.
THE INSTALLATION OF THIS APPLIANCE MUST MEET THE REQUIREMENTS OF THE CURRENT ISSUE FOR
ELECTRICAL INSTALLATIONS IEE WIRING.

7
USERS INSTRUCTIONS
The Trianco Aztec Combination boiler has been designed
and constructed to give years of trouble-free service and
these instructions are provided to assist you in obtaining
the best performance with the least trouble and cost.
The boiler is fully automatic in operation and requires little
attention other than the setting of the thermostat and any
external system controls such as a room thermostat and
time switch.
IMPORTANT
DO NOT COVER OR BOX IN YOUR BOILER, ALLOW AIR TO
CIRCULATE FREELY AROUND THE APPLIANCE
WARNING: DO NOT ATTEMPT TO SWITCH ON THE
BOILER IF THERE IS ANY POSSIBILITY THAT THE WATER
INSIDE THE HEAT EXCHANGER IS FROZEN
Before firing the boiler, ensure the system is full of
water and any valves fitted to the system are open.
Switch on the electrical supply to the boiler and after a few
seconds the boiler’s green and amber should illuminate.
Check that the time switch/programmer is ON and the
room thermostat is calling for heat.
Set the boiler to required temperature using the control
buttons.
Set the domestic hot water primary flow temperature
using the adjustable control on the front cover.
The domestic hot water outlet temperature should be set
by the installer. (Factory set @ 45°C)
Set the time switch/programmer to the times and
programs required.
The boiler will now operate automatically, cutting in and
out according to heat demand.
TO TURN OFF THE BOILER
Switch off the boiler at the time switch/programmer.
If the boiler is to be switched off for any length of time it is
recommended that the mains supply to the boiler is
switched OFF.
TEMPERATURE CONTROL
Your Trianco boiler is fitted with two adjustable
temperature control thermostats to regulate the
temperature of the domestic hot water and central
heating.
Use the Buttons on the facia to set the heating flow
temperature between 35°C – 75°C
Use the small control knob to adjust the flow temperature
to the domestic hot water heat exchanger between
60°C -85°C
The boiler is equipped with a thermostatic blending valve,
it is recommended when commissioning the boiler this is
set to 45°C to obtain the best performance from the boiler.
BOILER INDICATOR LIGHT
There are twelve LED indicator lights on the boiler fascia
panel these are:
LED 1 GREEN Power to the boiler.
LED 2 AMBER Illuminated - In run mode
Flashing - Temperature satisfied
LED 3 RED Boiler fault
If the RED LED light flashes, this means a fault has
occurred. This would result in the boiler continuing to
operate at a reduced output.
If the RED LED is permanently on, this indicates a fault has
occurred. (See simple fault finding on page 8).
LED 4 – 12 Green Heating & Hot water set
temperature lights.
The boiler has two neon indicators behind the fold down
panel indicating Hot water demand or Heating mode.
ROOM THERMOSTAT
The room thermostat should not be positioned near a
source of heat such as a radiator or exposed to the sun as
this will cause the central heating to switch off before the
room is up to temperature. Follow the manufacturer’s
instructions for best siting position for the thermostat.
FROST PROTECTION
If the boiler and central heating is shut down for many
hours during very cold weather, the water may be in
danger of freezing and, as such, it is advisable to protect
the installation with a frost thermostat.
Where the system is not protected, the boiler should be
left switched on and the room thermostat set to a low
setting e.g. 7°C (45°F) to prevent the building temperature
falling too low.
If the system is shut down for a long period during very
cold weather, it is advisable to completely drain the
system. However, frequent draining should be avoided,
especially in hard water areas, as this could lead to scaling
of the boiler waterways.
TIME SWITCH/PROGRAMMER
(Not Supplied) This will be a twin channel type capable of
switching Heating and Hot Water. The boiler is capable of
accepting all modern controls including Hive, Nest, Salus
etc.
Cleaning Casings
Use hot soapy water applied with a damp cloth for the
enamel, then dry with a soft dry cloth.
Simple Maintenance
Ensure that the natural ventilation around the boiler is not
obstructed. If fitted in a compartment, ensure all
ventilation grilles are clear.

8
SIMPLE FAULT FINDING
If the boiler fails to start for no apparent reason, make the
following checks before calling your service engineer.
Is the green LED light illuminated?
Check for blown fuse or thrown power breaker. If
replacement fuse or power breaker fails again, call your
service engineer.
If the red LED is permanently illuminated, contact
your service engineer.
Flashing red LED indicates an open circuit. The boiler can
still be operated. Your service engineer should be
contacted.
Amber light illuminated or flashing.
Check to see if all external controls i.e. programmer or
room thermostat is calling for heat.
Resetting the boiler
If a fault has occurred and the LED is illuminated but the
pump continues to run, then switching the power off for
30 seconds and then on again should reset the light. This
may be caused by the ambient temperature around the
boiler being too high. Check to ensure that any boiler
ventilation is not obstructed. If the fault reoccurs, contact
your engineer.
IMPORTANT: Electrical safety checks should be carried
out by qualified electrical engineer.
TECHNICAL DETAILS UNIT AZTEC 6kW AZTEC 9kW AZTEC 12kW
Electrical Input kW 6 9 12
Supply Current Amp 25 39 51
RCD Rating Amp 32 40 63
Minimum Cable Size mm 4 6 16
D.H.W Draw Off@40°C-45°C Ltr 80 95 110
Flow rate@45°C Ltr/min 10 10 10
Weight kg 65
Water Content litres 41
Width mm 500
Depth mm 300
Height mm 1010
Mains Supply 230V 50Hz
Max Operating Pressure 300 kPa / 3 bar
Test Pressure 600 kPa / 6 bar
Boiler Flow Temperature Adjustable between 35°C and 75°C
Limit Thermostats Factory set at 100°C
CH Flow & Return 22mm Compression
DHW Inlet & Flow 15mm Compression
Maximum Flow Temp CH 75°C
Pressure Gauge 0 – 4 bar
Pressure Relief Valve 3 bar
Diverter Valve Danfoss HSA3ND
Pump 25/60
Expansion Vessel 7Ltr charge 0.5mbar
Available System Head 3m
Casing Finish Stove enamelled white
Thermal Insulation Insulated with mineral fibre

9
INSTALLATION
Regulations
Installation of the boiler must comply with the following
British Standards and Regulations:
BS5449 – Forced circulation hot water central heating
systems.
BS7074-Part 1: Code of practice for sealed water systems.
The Building Regulations: Part ‘L’ (Northern Ireland)
Current I.E.E. Regulations
Local water undertaking By-laws.
Health and Safety at Work Act
The installer should be aware of his responsibilities under
the Act and provide where necessary, appropriate
protection for persons carrying out the installation. In the
interests of safety, a competent engineer should install the
boiler and all wiring must be carried out in accordance
with current IEE regulations.
IMPORTANT
ALL ELECTRICAL WORK MUST BE CARRIED OUT BY A
QUALIFIED ELECTRICAL ENGINEER TO CURRENT IEE
WIRING REGULATIONS.
UNPACKING THE BOILER
Carefully open the boiler carton, remove boiler and place
in a safe place until required.
NOTE: ALWAYS STORE THE BOILER IN A DRY PLACE PRIOR
TO FITTING.
SITING THE BOILER
IMPORTANT: NOT TO BE INSTALLED IN A SHOWER
COMPARTMENT OR BATHROOM
Ensure adequate clearance is allowed for making water
connections. Access is required to the front and the top of
the boiler for servicing. The boiler must also be fitted in a
dry, well ventilated position, which is not subject to
adverse temperature conditions. (See ventilation
requirements).
Care should be taken when siting the appliance to make
sure adequate access is available for future servicing of the
appliance. Please note that the PCB and heat exchanger
assembly may require removal during such times.
The boiler must be mounted on a suitable wall capable of
bearing the weight of the boiler.
Attach the two wall brackets supplied using suitable fixings
for the wall material. Making sure both brackets are secure
and level. See Fig 1.2 page 10 for bracket positions.
Once the brackets are secure the boiler can be lifted into
position locating the boiler lugs on to both wall brackets.
To aid in lifting the boiler the case panels must be
removed. Do not attempt to lift the boiler with the panels
attached as this will damage the case.
Clearances
Please allow adequate clearance in front of the boiler for
servicing and end user access.
FLOW & RETURN CONNECTIONS
Fig. 1
Fig. 1.1

10
Fig 1.2

11
VENTILATION REQUIREMENTS
If the appliance is to be fitted in a confined space or
compartment it is a requirement that adequate ventilation
is provided to prevent the overheating of the boiler
controls. Aeration of 110 cm² will be required to the
compartment, in both high and low positions (see Fig. 2).
WATER SYSTEM
IMPORTANT: USE ONLY COMPRESSION FITTINGS WHEN
CONNECTING THE BOILER TO THE CENTRAL HEATING
SYSTEM.
ISOLATION VALVES MUST BE FITTED
The installation must comply with the requirements of the
following codes of practice.
BS 5449 Part 1 Forced Circulation Hot Water Systems
BS 7074 Part 1 Code of Practice for Sealed Water
Systems.
BS 7593 Treatment of water in domestic hot water central
heating systems.
The water system must be thoroughly flushed out.
Fill the system. Vent all air from system. Clear any air locks
and examine the system for water leaks.
IMPORTANT: ENSURE ALL SERVICE VALVES ARE IN OPEN
POSITION.
The boiler is supplied with Dia. 22mm tail pipes at the
base of the boiler for connection to the heating system
(see Fig: 1). The boiler is also supplied with 15mm tail
pipes for connection to the DHW circuit (see Fig: 1).
The boiler must be installed using 22mm compression
fittings.
Model Minimum Flow Rate / Min
6kW 8 litres
9kW 10 litres
12kW 12 litres
Aztec boilers are approved for use on fully pumped open
vented systems and sealed systems. Where thermostatic
radiator valves are fitted it will be necessary to fit a bypass
to obtain minimum flow rates.
IMPORTANT: IF MINIMUM FLOW RATES ARE NOT
OBTAINED THE BOILER MAY GO TO LOCK OUT ON HIGH
LIMIT THERMOSTAT.
System must be flushed out before adding inhibitor to BS
7593: 1992 treatment of water in central heating boiler.
IMPORTANT: THIS BOILER IS TO BE FITTED ON FULLY
PUMPED SYSTEMS ONLY.
Pump
WARNING! Risk of injury and damage to property!
Incorrect commissioning can lead to injuries to persons
and damage to property.
Commissioning by qualified personnel only!
Depending on the operating status of the pump or system
(fluid temperature), the entire pump can become very
hot.
Touching the pump can cause burns!
Operation
The pump is operated using the operating dial. By turning
the dial, different control modes can be selected, and the
delivery head or constant speed can be set.
NOTE: All settings are retained if the mains supply is
interrupted.
Domestic Hot Water
It is recommended the Hot water is timed to be on 15
minutes before water will be required at the tap.
The domestic hot water blending valve is factory set to
Minimum to give 45°C outlet temperature. This can be
adjusted as required but note that any increase will reduce
the volume of water available.
Fig. 2

12
SEALED WATER SYSTEM REQUIREMENTS
The installation must comply with the appropriate
requirements of the current issue of BS4814, BS5449,
BS6798 and BS7074 Part 1 and 2.
Safety Valve
A 3-bar safety valve is fitted within the unit. The drain
must be routed to the outside of the building. The drain
must not discharge above an entrance or a window or any
public access area, be clear of any electrical fittings and
positioned so that any discharge can be seen.
Expansion Vessel Capacity
A diaphragm type expansion vessel, conforming to the
current issue of BS4814. The expansion vessel must be
connected to the systems at a point close to the inlet side
of the circulating pump. The expansion vessel volume
depends on the total water system volume and the initial
system design pressure. For any system an accurate
calculation of vessel size is given in the current issue of
BS5449 and BS7074 Part 1.
The water content of the boiler is given in the technical
specification. Note a higher initial design pressure requires
a larger volume expansion vessel.
The charge pressure must not be less than the static head
of the system, which is the highest point of the system
above the expansion vessel.
Capacity of Expansion Vessel
Where design information is not complete the following
chart (page 11) can be used for selecting the size of the
vessel, it should be noted that the size given in the table
take account of fault conditions.
Note the internal 7 litre expansion vessel might not
accommodate the entire system volume.
NOTE: Failure to ensure the correct vessel size could
result in premature failure of the expansion vessel which
in turn may adversely affect other components in the
system i.e. circulating pump and diverter valve.
System Temperature
The normal running temperature of the heating system is
75°C, if a fault was to occur then the safety device would
allow the system temperature to rise to 100°C. It is
recommended that this figure be used in the calculations
of vessel size.
Pressure Gauge
A 0 to 4 bar pressure gauge is fitted within the unit.
Inhibitor
If using an existing system take care to drain down the
entire system including the radiators, then thoroughly
clean out before fitting the boiler. Attention is drawn to
the current issue of BS5449 and BS7593 on the use of
inhibitors in central heating systems.
Drain Tapping
A drain tapping is provided on the boiler. An additional
tapping must be provided at the lowest point of the
system, which will allow the entire system to be drained.
System Makeup
Water loss from the system should be replaced from a
makeup vessel connected to the system. This vessel should
be higher than the top of the system. Alternatively,
provision can be made by pre-pressurisation of the system
via a temporary hose connection and through a double
check valve (non-return) and stop valve.
There must be no permanent connection to the mains
water valve supply even through a non-return valve.
Safety valve setting (bar gauge) 3 Bar
Vessel charge and initial system pressure (bar gauge) 0.5 1.0 1.5
Total water content of system (litre) Vessel volume (litre)
25 2.3 3.3 5.9
50 4.7 6.7 11.8
75 7.0 10.0 17.7
100 9.4 13.4 23.7
125 11.7 16.7 29.6
150 14.1 20.1 35.5
175 16.4 23.4 41.4
200 18.8 26.8 47.4

13
AZTEC COMBI SCHEMATIC LAYOUT CENTRAL HEATING MODE
Fig 3
SEALED SYSTEM PIPING SCHEMATIC DIAGRAM
AZTEC COMBI SCHEMATIC LAYOUT DOMESTIC HOT WATER MODE
Fig 4
Fig 5
C/H Return C/H Flow
Plate Heat Exchanger
DHW
Cold Inlet
Diverter
Valve
Expansion
Vessel
C/H
Boiler
DHW
Boiler
Pump
Flow
Switch

14
WIRING INSTRUCTIONS
All electrical work must be carried out in accordance with
current IEE wiring regulations.
Before commencing installation check power supply to
property to ensure that there is sufficient current and
voltage available for size of boiler fitted. Take into
account requirements of other electrical appliances, the
boiler must be connected to the mains supply by means
of a double pole linked switch with 3mm contact gap in
both poles.
IMPORTANT:
After completing electrical installation work preliminary
safety checks should be carried out as described in
BS 7671:2001
The electrical supply requirements:
The 6kW boiler supply should meet the requirements of
EN61000-3.3.
The 9kW boiler must be installed in premises having a
service supply > 100A per phase and meet the
requirements of IEC 60417-5855.
The 12kW boiler must be installed in premises having a
system impedance of not more than 0.1939 + 0.1939Ω.
A double pole RCD with a trip level sensitivity of 30ma can
be used capable of breaking full load current to
BS EN61008: 1994
NOTE: RCD unit can be used as the isolating switch if
mounted close enough to the boiler.
Miniature circuit breakers MCB’s MUST be fitted between
RCD unit and boiler and RCD and any external controls.
Refer to technical specification. For MCB ratings refer to
wiring diagram.
It is important the correct size MCB is used in the supply
from the RCD to the boiler.
ELECTRICAL CONNECTIONS
WARNING: THIS APPLIANCE MUST BE EARTHED.
The mains connection block is located inside the boiler on
a bracket at the bottom left hand side of the boiler which
can be directly wired to the boiler MCB. Use the correctly
rated cable.
IMPORTANT: CORRECT POLARITY MUST BE OBSERVED
WHEN BRINGING THE MAINS SUPPLY INTO THE BOILER.
TERMINAL CONFIGURATION
Fig 7
Fig 6
ALTERNATIVE METHODS OF
FILLING A SEALED SYSTEM
Fig. 8

15
Fig. 9 Internal Wiring diagram

16
SERVICING
To ensure reliable operation of your Aztec electric
combination boiler, it is recommended that you have your
boiler serviced once a year.
The person(s) who services or carries out any remedial
work, i.e. electrical fault finding must have suitable
engineering qualifications.
Isolate mains supply before carrying out any service
work.
Check all electrical connections on PCB and electric
elements to ensure they are secure and clean.
Check electrical insulation on wiring.
Ensure all air grilles are clean and free from obstructions.
Inspect seals around elements and the heat
exchanger’s top and bottom flanges.
PARTS REPLACEMENT
Casing Removal
Isolate electrical supply to the boiler.
Remove 2 top fixing screws securing front case in position.
Lift front panel upwards and away from boiler.
IMPORTANT: All electrical connections should be
checked. Loose connections can cause problems.
The boiler is fitted with two manual reset high limit
thermostats. Before replacing any part, ensure that
thermostat does not require resetting.
PCB ASSEMBLY REPLACEMENT
Note: The PCB is supplied with the element jumper fitted
suitable for 12kW boiler. When a 6kW or 9kW output
boiler is required, the element jumper must be
repositioned.
Ensure electrical supply to the boiler is isolated.
Remove the front casing and disconnect the temperature
button cables from the PCB.
Disconnect the pump and call plug, the thermistor
plug, the fan (where fitted) and high limit thermostat plug.
Disconnect all element cables. N.B. Take note of wiring
arrangement before disconnecting.
With all elements disconnected, again taking note of
wiring arrangement, carefully disconnect and remove the
element cables from the PCB. Important: Care must be
taken.
Disconnect the remaining red and black power cables from
the PCB.
Finally remove the 2 fixing screws holding the PCB
mounting bracket in position and remove the PCB from the
unit.
Re-fit in reverse order on reassembly always refer to wiring
diagram.
HIGH LIMIT THERMOSTAT REPLACEMENT
Ensure electrical supply is isolated to boiler
The high limit thermostat can be found fixed to top front
face of boiler.
Remove 2 terminal connectors from high limit thermostat,
loosen retaining straps and slide thermostat out from
behind.
Important when replacing thermostat ensure a heat sink
compound is used between back of thermostat and face of
boiler. (See Fig. 10 for positioning).
Inspect retaining straps and replace where necessary.
THERMISTOR REPLACEMENT
Isolate electrical supply to boiler.
The thermistor is located fixed to top front face of the
boiler above the high limit thermostat.
Disconnect from PCB board and slide out from behind
retaining strap.
Important when replacing thermistor ensure a heat-sink
compound is used between thermistor and boiler body
(see Fig. 10 for positioning).
Fig. 10

17
ELEMENT REPLACEMENT
Isolate electrical supply to boiler.
Drain down system.
Disconnect terminal connectors from high limit
thermostat
Remove thermistor from behind the retaining strap.
Disconnect electrical elements and earth wire.
Disconnect compression fitting from the top and bottom of
boiler.
Boiler unit can now be carefully removed.
Remove 8 fixing screws on top flange with and withdraw
the element assembly.
Remove bottom element positioning bracket.
Remove damaged element.
Refit in reverse order and ensure element seals are fitted.
Check for continuity through 2 terminals on each element.
IMPORTANT: Inspect all seals and change where
necessary.
FAULT FINDING
Red LED permanently illuminated indicates one of the
following faults.
High limit thermostat has operated or faulty electrical
connections
The boiler has two high limit thermostats fitted, one on the
heat exchanger and one on the tank. The high limit
thermostat on the heat exchanger is fitted to the front top
of the stainless-steel heat exchanger and secured in
position with 2 retaining clamps. The tank high limit
thermostat is fitted onto the tank on the left-hand side at
the top. Check electrical connections on thermostat and
PCB to check thermostat has not failed using a multi-meter
check continuity across terminals of thermostat. To reset
press the red button in centre of thermostat. The
thermostat may have tripped due to one of the following:
Faulty circulation pump.
Isolation valve on system closed.
Air trapped in system.
Out of calibration limit thermostat.
Temperature settings on PCB board incorrect.
No water in system.
Thermistor
The boiler has two thermistors fitted, one on the heat
exchanger and one on the tank. The heat exchanger
thermistor is fitted to the front top of the heat exchanger
and secured in position with a clamp, the other end
terminates with a white connector that plugs on to the PCB
The tank thermistor is fitted on the left hand side of the
tank at the top. Check the connections on the board to
make sure it is correctly fitted, also inspect the thermistor
for any broken wires.
Mains Inlet Wiring
If the mains supply to the boiler is wired incorrectly on the
inlet terminal block. Check polarity.
PCB Damage
Inspect the LED lights and the boiler temperature control
adjuster for any damage to connections to PCB controller.
Voltage Drop
If the voltage drops below 207 volts.
Red LED flashes indicates one of the following faults.
Poor electrical connection
Check the electrical connections to the elements and the
PCB controller, a poor controller would show up a fault.
Element Failure
To check elements for failure, disconnect each individual
element and check continuity through the element if there
is continuity between the two terminals the element is ok.
Check each element individually replacing the electrical
connectors after testing.
Element Cables
If there is a break in the element cable, this would show up
as a fault. Check all element cables and connections.
PCB Running Temperature
The PCB control unit has a built in temperature control
sensor which protects the PCB from overheating, if the
board was to overheat the sensor would detect the high
temperature and shut off the power to the board until the
board temperature has returned to normal running
temperature. The boiler will resume operation, but the red
light will continue to flash to indicate a fault has occurred.
To reset the board the power must be turned off for 30
seconds then switched on again.
To differentiate between a temperature or element
problem, switch off the power supply to the boiler allow
the boiler to cool down then switch the power back on, if
the LED continues to flash then check elements and
connections.

18
Green LED
If the green LED is illuminated but the boiler is not
functioning, check that the external controls fitted are
calling for heat.
Blown Fuse on Board
The fuse is located at the top of the PCB (fuse type 20mm
1000Ma anti surge)
The fuse covers external controls.
RCD UNIT TRIPS
Check that the RCD unit is correctly rated for boiler size. If
under size change. Inspect mains terminal block wiring for
short-circuiting. Check electrical elements for earth
continuity, if element is found to be faulty fit new element.
Other Information
Thermistor Values
Element Jumper Connections
It is important to set the jumpers to the required boiler
output before turning the boiler on. Boilers are factory
set to 6kW
Thermistor Values
Temperature (°C) Resistance Value (Ohms)
0 32554
5 25339
10 19872.2
15 15698.5
20 12487.7
25 10000
30 8059.1
35 6543.7
40 5329.9
45 4371.7
50 3605.3
55 2988.7
60 2490
65 2084.4
70 1753
75 1480.9

19
22
23
NO HEAT - PERMANENT GREEN LIGHT
IS THE
PROGRAMMER
TURNED ON I.E.
CALL SIGNAL?
IS THE HEAT EXCHANGER
GETTING UP TO
TEMPERATURE - AMBER ON
OR FLASHING?
CHECK
EXTERNAL
CONTROLS ARE
CALLING FOR
HEAT
ARE ISOLATING
VALVES OPEN?
IS THE PUMP
RUNNING?
OPEN
ISOLATING
VALVES
CHECK LIVE & NEUTRAL
TO PUMP
LIVE & NEUTRAL
OK?
CHECK SYSTEM
PRESSURE & PIPE-
WORK FOR AIRLOCKS
CHANGE PUMP
NO
YES
NO
YES
NO
YES
YES
CHANGE PCB
NO
IS CALL WIRE LIVE I.E. LINE
VOLTAGE?
CHECK
ELECTRIC
SYSTEM
CIRCUIT
NO
YES
YES

20
PERMANENT RED LIGHT
IS INCOMING POWER
SUPPLY OK?
R
EPLACE
THERMISTER
CABLE
H
AS THE HIGH LIMIT
STAT TRIPPED?
R
EPLACE FAULTY
CABLES OR
CONNECTIONS
DOES THE BOILER GO
FROM GREEN TO
AMBER THEN RED?
C
HANGE PCB
R
EFIL TO 1 BAR
&CHECK FOR
LEAKS
IS THE SYTEM
PRESSURE
SUFFICIENTLY
CHARGED?
IS THE THERMISTER
CABLE FAULTY?
Y
ES
A
RE THE LIMIT
STAT
CONNECTIONS
OK?
N
O
N
O
N
O
C
HANGE PCB
Y
ES
N
O
CHECK INCOMING SUPPLY
CROSS POLARITY?
CORRECT VOLTAGE?
CORRECT RCD?
Y
ES
D
OES THE BOILER
GO STRAIGHT TO
RED LIGHT?
Y
ES
Y
ES
R
E-SET HIGH LIMIT
STAT
Y
ES