WALL MOUNTED STAINLESS RANGE

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S E R V I C E M A N U A L

ISSUE: 1- Dated: August 2006
WM SERIES (including WA5 value boiler)

AUTOMATIC FILL, WALL-MOUNT WATER BOILERS

CONTENTS

Section: Page No:

Contents p.1
Introduction p.2
Principle of Operation p.3
1 .0 Technical Specifications p.3 - 4
2.0 The Tank p.4
3.0 The LCD Display p.5
4.0 The Sensing Probes p.6
5.0 Thermistor p.6 - 7
6.0 Temperature Adjustment p.7
7.0 Heating Elements p.7 - 8
8.0 Triacs p.8
9.0 Printed Circuit Boards (diagnostics) p.9 - 10
10.0 Thermal Cut-outs (over-boil & boil-dry) p.10
11.0 Solenoid Valve (water pressure) p.11
12.0 Water Draw-off Tap p.11
13.0 Descaling p.12
14.0 Fault-Finding p.13
15.0 Warning Messages p.14 - 15
16.0 Exploded Drawing & Wiring Diagrams p.16 - 18

INTRODUCTION:

This manual has been designed to be a guide for service engineers. It includes descriptions of all serviceable parts, a fault-finding guide, exploded drawings and wiring diagrams.

WM-series:
The WM-Series wall-mount water boilers were launched in March 2006 to supersede the award winning “WA” series which was manufactured between 1996 and February 2006. The new “WM” series have taken the proven reliability and robust construction of their predecessors and applied the latest advancements in electrical design and technology to produce a catering boiler which is the most advanced of its kind, yet easy to use and built to last.

WA5
The WA5 has been in production since 1999 and offers Instanta quality and reliability but with slightly lower specification and less style.

Both the “WM” series and WA5 are inspected and tested in accordance with the company’s ISO9001 Quality Management System and ISO14001 Environmental Management System and conform with the protection requirements of the following standards and specifications:

EMC W89/336/EEC Electro-Magnetic Compatibility (EMC)
EN 50-081-2 Generic Emission
EN 50-082-2 Generic Immunity

ROHS Manufactured in compliance with the requirements of the RoHS Directive

WRAS Manufactured in compliance with the requirements of the UK Water Regulations/Bylaws

All models in this range are similar in construction, but vary in size.

PRINCIPLE OF OPERATION:

When switched on, the machine first checks for water at the low-level (bottom) probe. If no water is sensed at the probe, the solenoid is energised. If no water is detected after approximately 5 minutes the solenoid switches off and the LCD display reads “check water supply”. When water is detected at the bottom probe, the heating element(s) is switched on to heat the water to the correct temperature. When the set temperature is reached, the solenoid is pulsed on and off to allow water into the boiler. The amount allowed into the boiler is controlled to maintain the temperature. The heating element stays on during the filling cycle until the normal-operating probe and specified temperature is reached.
When the boiler has reached the normal-operating probe and the correct temperature, it goes into ‘idle’ mode. The heating element is pulsed periodically to maintain temperature.

1.0 TECHNICAL SPECIFICATION:

WM3 & WM3SS

Voltage: 220-240V single-phase 50/60Hz
Supply: AC
Rated Input: 3.0kW
Fill Type: Automatic Fill
Recovery per Minute: 0.5 Litres
Rapid Draw-off: 3.0 litres (6 pints)
Heat-up time: 12 minutes (from cold to full capacity)
Height: 452 mm
Width: 332 mm
Depth: 208 mm (excluding tap protrusion of 90mm)
Avg. Power Consumption: 0.10 (kw/hour - standby)

WM7 & WM7SS

Voltage: 220-240V single-phase 50/60Hz
Supply: AC
Rated Input: 3.0kW
Fill Type: Automatic Fill
Recovery per Minute: 0.5 Litres
Rapid Draw-off: 7.0 litres (12 pints)
Heat-up time: 25 minutes (from cold to full capacity)
Height: 498 mm
Width: 350 mm
Depth: 220 (excluding tap protrusion of 90mm)
Avg. Power Consumption: 0.12 (kw/hour - standby)

WM15-3 & WM15-3SS

Voltage: 220-240V single-phase 50/60Hz
Supply: AC
Rated Input: 3.0kW
Fill Type: Automatic Fill
Recovery per Minute: 0.5 Litres
Rapid Draw-off: 15 Litres (26 pints)
Heat-up time: 57 minutes (from cold to full capacity)
Height: 545 mm
Width: 350 mm
Depth: 250 mm (excluding tap protrusion of 90mm)
Avg. Power Consumption: 0.13 (kw/hour - standby)

WM15-6 & WM15-6SS

Voltage: 220-240V single-phase 50/60Hz
Supply: AC
Rated Input: 6.0kW
Fill Type: Automatic Fill
Recovery per Minute: 1.0 Litres
Rapid Draw-off: 15 Litres (26 pints)
Heat-up time: 28 minutes (from cold to full capacity)
Height: 545 mm
Width: 350 mm
Depth: 250 mm (excluding tap protrusion of 90mm)
Avg. Power Consumption: 0.13 (kw/hour - standby)

WA5

Voltage: 220-240V single-phase 50/60Hz
Supply: AC
Rated Input: 3.0kW
Fill Type: Automatic Fill
Recovery per Minute: 0.5 Litres
Rapid Draw-off: 5.0 litres (8 pints)
Heat-up time: 18 minutes (from cold to full capacity)
Height: 420 mm
Width: 285 mm
Depth: 200 mm (excluding tap protrusion of 85mm)
Avg. Power Consumption: 0.10 (kw/hour - standby)

2.0 THE TANK:

The tank lid is secured using M4 stainless steel screws. The lid is sealed with an EPDM rubber gasket. Silicone sealant secures the gasket to the tank, and the lid is sealed with silicone grease. The tank body and lid are made from type-304 stainless steel while the internal baffle plates are made from type-316 stainless steel (type-316 is more resistant to the corrosive properties and minerals found in some mains water supplies in specific parts of the UK.

3.0 THE LCD DISPLAY - Digital Program Menu (NOT WA5):

The LCD display informs the user of the boiler’s status (e.g. filling, heating, ready etc.). The display also informs the user of potential fault conditions (e.g. no water supply, clean probes, etc.).

The LCD display in conjunction with the On/Off button also gives access to the program menu which allows various settings to be selected.

To access the program menu:

• Switch the boiler off and back on again - within a few seconds of the boiler being switched on again, press and hold the On/Off button in for approximately 10 seconds, until the display reads “program mode”.
• Continue to press the On/Off button to proceed through the 15 menu selections until the desired mode is reached.
• To select the mode, hold button in for 3 seconds.
• Program Menu is as follows:

1. TEMP SET (adjustable: 80-99^Celcius [default: 98^C])
2. SET TIME (not applicable)
3. EXIT (Exit program mode)
4. USE FILTER (not applicable)
5. FILTER SIZE (not applicable)
6. POWER MODE (last-used, always-off, always on)
7. ECO MODE (enable-disable) – NOT WM3 MODELS
8. ELEMENT(S) (select KW rating of boiler: 1.5KW - 18KW)
9. SHOW CLOCK (enable-disable)
10.BRIGHTNESS (Brightness High, Brightness Low)
11.SUPPLY IN (takes a reading of mains supply voltage)
12.TEST MODE (shows which sensors are registering water)
13.ADC VALUES (manufacturers test values)
14.DEFAULTS (returns boiler to factory-set defaults)
15.EXIT (Exit program mode)

PLEASE NOTE: All new XE870 circuit boards are supplied with default settings suitable for standard 3KW models.

If a new PCB is fitted to a WM15-6 or WM15-6SS, then the “PROGRAM ELEMENTS” mode will need to be accessed and the setting adjusted to the appropriate KW rating (6.0KW for WM15-6).

4.0 THE SENSING PROBES:

Sensing probes are used to detect the presence of water within the tank (5-13 second response time), using a small electrical current to make a circuit via the water.

They are made-up from a PTFE insulator with a chrome-plated brass rod through the centre.

There are five level sensing probes inside the tank (from bottom to top):

1. Low-level Sensor - Yellow wire (CLEAN PROBES-1)
2. Eco Sensor (NOT WM3) - Grey wire (CLEAN PROBES-1)
3. Normal Operating Sensor - Brown wire (CLEAN PROBES-2)
4. De-scale warning Sensor - Orange wire (CLEAN PROBES-2)
5. Overfill detection Sensor - Red wire (CLEAN PROBES-2)

NOTE-1: Only the low-level and Normal Operating sensors are used in normal operation.

NOTE-2: The WA5 model only has two level sensors – (low-level and normal operating)

Common problem: Hard-water in some parts of the UK causes a build-up of lime-scale on the sensing probes, which acts as an insulator (e.g. the sensor is no-longer able to detect the presence of water). When a sensor becomes insulated, the water level will switch to a different sensor and the CLEAN PROBES message will display. This will be followed by a number 1 or 2 (dependant on which sensor is scaled-up – see above).

Water with low mineral content: The level sensing probes depend on the mineral content within the mains water supply in order to detect the presence of water in the tank. In some parts of the UK (e.g. parts of Scotland) the water is very pure leading, in extreme cases, to the probes being unable to register the presence of water. Similarly, some off-shore facilities use “treated” water with the mineral content removed, again resulting in the same problem. In most circumstances, the replacement of the standard level sensing probes with an alternative “marine” probe which has a much larger surface area, will resolve the problem (Part No. for Marine Probes: PRB1S/A)

5.0 THE THERMISTOR (thermal resistor):

The thermistor is an electronic device used in place of a thermostat, to measure the temperature of water. It is constructed using a thermally sensitive resistor which exhibits changes in electrical resistance with even a slight change in water temperature, making it extremely accurate (+/- 1.2 degrees Celsius).

On the “WM” series and WA5, the thermistor is stuck to the outside of the tank-front using metal-set putty.

POSITION: - IMPORTANT: POSITION OF THERMISTOR ON THE TANK IS BETWEEN THE HEATING ELEMENT AND LOW-LEVEL SENSOR – ON FRONT OF THE TANK.

Removal/replacement of thermistor: - To remove the old thermistor, chip it off using the tip of a screwdriver.

To ensure that the new thermistor is correctly fitted to the tank, the metal-set compound must be thoroughly mixed. To do this, fold the compound between your
fingers for at least one minute. Place the thermistor into the mixed compound and apply the compound onto the cold tank,* ensuring that the head of the thermistor is completely covered. The metal-set should completely harden in approximately 5 minutes.

* It is strongly advised that the tank should be cool before application of Metal-Set

6.0 TEMPERATURE ADJUSTMENT:

The water temperature on the “WM” series boilers can be digitally adjusted between a range of 80 and 99^Celsius in 1^C increments.

To adjust temperature, access the programme menu via the LCD display (see Section-2). The factory-default temperature setting is 98^Celsius.

NOTE: For most end-users serving hot drinks, the optimum temperature setting will be 97-98^Celcius.

WA5 models - Temperature Adjustment:

The temperature is adjusted via a potentiometer which is mounted on the P.C.B. This can be adjusted using a very small electrical screwdriver.

7.0 HEATING ELEMENT(S):

The heating elements are made from Incoloy800 material, which gives them a long life expectancy. They are sealed into the tank by three silicone rubber washers and secured by three 1/4”BSP brass lock-nuts.

ELEMENT RATING: 3.0KW, 230V

RESISTENCE: Between 19 and 20 Ohms

AMPS: The elements will draw between 10 and 11 amps.

If the element has blown it will have an open circuit. To test this use a simple PAT test.

Boil-dry Protection:

Each element has a brazed “hot-return” fitting, which accepts a stud-mount, 120^C thermal cut-out switch. The live input to the element is directed through the thermal cut-out switch. If the element overheats (boil-dry situation etc,), the thermal switch picks up the rise in temperature and breaks the live supply to the heater. If this happens, the thermal switch will need to be reset by pushing in the small button on the top of the switch-body.

8.0 THE TRIAC:

The triac is a device used to switch the heating element on via a control signal from the P.C.B. The triac generates heat, which has to be dissipated. This is done by bolting it to the aluminium wiring bracket using heat-sink compound between the surface of the triac and the aluminium bracket.

NOTE: WM15-6 (6KW) Model Only: The triac is mounted to the painted aluminium back-panel instead of the PCB bracket – This is to provide a larger-surface area heat-sink for dissipating the extra heat generated by the XE854 triac, which is driving two 3KW elements on the WM15-6 model.

There are 2 types of triac used on the “WM” series:

XE851 - all 3kw models and
XE854 - WM15-6 models

If the triac fails, in 90% of cases it will fail in the closed position. This causes the heating element(s) to remain on. If this happens, the machine will overheat. When steam enters the overflow vent pipe, the over-boil safety cut-out will detect a rise in temperature and switch off power to the elements.

If the triac has failed in the closed position there will be continuity between the live element terminal (PCB) and live into the triac (GREY wire).

To test if the triac has failed (closed circuit), re-set thermal cut-out (if necessary), leave machine plugged in and turn off at the ON/OFF switch (front panel). If the machine continues to heat when switched off, the triac is faulty. If not, refer to faultfinding “over-boiling”.

9.0 PRINTED CIRCUIT BOARDS:

XE870 - MAIN P.C.B. (NOT WA5)

Operating Voltage: 190V – 265V AC @ 50/60Hz
Frequency Range: 47-65 Hz
Fuse Rating: 315mA 250V AC
Operating temp: 0–70^C

Located on the aluminium wiring bracket, to the left of the tank assembly. This P.C.B. controls the main functions of the machine, monitoring the water level, water temperature, water supply etc.

There are four board-mounted LED’s on the XE870 main PCB as follows:

Continuous Flashing Amber = Processor is working OK
Green = Mains Supply to PCB
Red = Heating element is on
Amber = Boiler filling with water

The P.C.B. can be configured for use on either: 3 or 6kw boilers. When supplied from new, the software default is for 3KW models. To adjust and configure for use on a 6.0KW boiler, the “PROGRAM ELEMENTS” mode will need to be accessed and the setting adjusted to the appropriate KW rating (6.0KW for WM15-6) as described in SECTION-2 “LCD Display”.

This configuration of the P.C.B. to match the KW rating of the boiler determines how much water the software tells the inlet valve to put into the machine in one pulse.

Fault Diagnostics:

If a fault is detected, the user is warned via the LCD display. There are two categories of warnings:

1 - Simple Warnings:
CHECK WATER
NO WATER
CLEAN PROBES-1
CLEAN PROBES-2

Any of the above messages may be seen – the display will alternate between the boiler status (e.g. BOILER READY) and the warning message. An amber “exclamation mark” may also illuminate in the display. These warnings are not critical and should be dealt with when it is convenient to do so. To clear the message, switch the machine off at the mains supply and switch back on again.

2 - Critical Warnings:

In the event of a serious malfunction, the red spanner in the display will illuminate together with the message “Call Supplier”, alternating with one of the following messages.
THERMISTOR-O/C
HEAT/THERM FAIL
OVERFILL,

SEE CHART ON PAGE: 15/16 for details of the warnings and the possible causes.

XE871 - LCD Display P.C.B. – All “WM” models:Operating Voltage: 8-17v DC @ 0.2 Amps max
Display: 16 characters x 2 lines
Inputs: On/Off button, Eco-mode button

The XE871 is purely a display system. The boiler will continue to function if it is faulty, removed or damaged. The integrity of the system is reliant on the Main XE870 P.C.B. in terms of failure and safety.

See Section-3 “LCD Display” for details on how to access the program mode and make adjustment to settings.

WA5 MODELS:

XE150B P.C.B – All WA5 models:

The XE150B P.C.B. controls all main functions of the machine, monitoring the water level, water temperature, water supply etc. If a fault is detected the user is warned via a tri-coloured L.E.D. light on the front of the machine. Some faults render the boiler inoperative whilst others will only give warning flashes – as follows:

Normal operation with non-critical error (these should be attended to as soon as possible):

L.E.D. COLOUR MEANING
Flashing Green Bottom probe is scaled up
Flashing Orange Boiler cannot obtain water from mains supply
Critical faults which prevent operation of machine:

L.E.D. COLOUR MEANING
Flashing Orange Cannot fill boiler to bottom probe
Flashing Red Heating element, triac or thermistor have failed
Alternate flashing Red/Green Thermistor has failed, become disconnected or its wires are damaged.
Solid Red changing to Flashing Red Safety cut-out has tripped (due to over-temperature) all machine functions have been shut down.

10.0 - THERMAL CUT-OUTS:

Over-Boil Protection – (Overflow-vent)

All machines have a thermal cut-out switch situated on the overflow vent pipe. Its function is to protect in the event of an over-boil situation arising - the thermal switch will cut power to the heaters. After about 1-hour, the LCD display will show the message “HEAT/THERM FAIL”. (Note: Before 1-hour, the display does not indicate any fault – a normal message e.g. “Boiler Ready” is displayed). If the over-boil cut-out has activated, switch the boiler off at the wall and back on again in 10 minutes once the boiler has cooled. The thermal switch will reset itself and work as normal.
(Note: WA5 notifies fault conditions via a flashing L.E.D. not a display read-out – see p.9)

Boil-Dry protection - (Element[s])

All heating elements have individual thermal cut-out switches fitted to them. If the element overheats (boil-dry situation etc,), the thermal switch picks up the rise in temperature and breaks the live supply to the heater. After about 1hour, the LCD display will show the message “HEAT/THERM FAIL”. If this happens, the thermal switch will need to be reset by pushing in the small button on the top of the switch-body.

11.0 THE SOLENOID VALVE

The cold water inlet valve can operate between 2 bar and 7 bar (28-100psi) mains pressure. The only serviceable part on the valve is the coil. The coil is susceptible to water damage from steam or water leaks. This can lead to P.C.B. problems, e.g. a blown 315mA fuse or electronic components.

Disconnect boiler from electrical supply before replacing the solenoid valve.

NOTE: Always check 315mA fuse ON P.C.B. when replacing solenoid coil.

Mains Water Pressure:

MAINS WATER PRESSURE RANGE: Between 2.0 and 7.0 bar (28 and 96psi)

Incoming mains water pressure can vary wildly from site to site and can also fluctuate dependent on the time of day (water pressure often increases at night). In extreme cases, this can take the mains water pressure outside that at which the boiler can operate. In-coming mains water pressure of more than 100psi (7.0bar) can bypass the solenoid valve and cause an overflow situation. In such circumstances, a pressure reduction valve should be fitted to the pipework (before the machine), to bring it to a level that the machine can cope with.

Similarly very low mains water pressure (below 20psi) can also result in the solenoid valve being bypassed - insufficient water pressure prevents the valve from seating correctly, although this is much less common.

12.0 - WATER DRAW-OFF TAP:

The tap washer and/or spring will occasionally require replacement.

To replace the tap washer: (Part No. TP1001/L)

? Switch machine off.
? Drain off water.
? Unscrew bonnet and remove the upper tap assembly out of the tap body.
? Remove the old washer from the tap spindle and firmly push the new washer onto the spindle.
? Screw the upper assembly back onto the body.

To replace the tap spring. (Part No. TP1007/L)

? Switch machine off.
? Drain off water.
? Push the pin out of the tap handle.(the pin has a bend in the middle)
? Unscrew the plastic bonnet to replace broken spring.(Small diameter down)
? Replace bonnet and handle.

13.0 - DE-SCALING (Including cleaning probes):

Common problem: Hard-water in some parts of the UK will usually result in a build-up of lime-scale within the tank. This can lead to a variety of different problems:

(i) One of the more common problems is caused by scale deposits coating one (or more) of the five sensing probes - The scale acts as an insulator (e.g. the sensor is no-longer able to detect the presence of water).

(ii) Heavy scale deposits on the inside of the tank can also affect the accuracy of the temperature sensing device (thermistor), which is fixed to the outside of the tank with metal-set putty – The scale acts an insulator between the water and the stainless steel tank-body, thus reducing the responsiveness of the thermistor, which can eventually lead to an over-boil situation arising.

(iii) A heavy build-up of scale on the heating element(s) can also reduce their life expectancy.

De-scaling Instructions:

? Isolate power supply.
? Remove the boiler case
? Remove tank lid and internal baffle plates.
? Remove as much loose scale as possible by hand.
? Remove any hard scale coating the level sensing probes and insulators, using a non-metallic scouring pad.
? Use a good de-scaler such as “Renegite” (Part No. ACC303) to remove hard scale deposits. Mix 1-2 packets in hot water and pour into tank. Leave for approximately 20 minutes.
? Flush tank out with copious water, ensuring that all traces of de-scaler are removed before re-assembly.

NOTE: There is a drain plug on the bottom of the tank which can be removed to evacuate the tank. Always remember to replace.

14.0 - FAULT FINDING:

This section contains a list of faults and causes that the machine may encounter.

MACHINE SYMPTOM CAUSE
Dead P.C.B. faulty - (315mA fuse or transformer)
No mains input (installation or outside interference fault)
On/Off switch faulty
Unsound terminal connection
Blown fuse in plug
Bad connection in plug (mains lead fault)
Overfilling Water pressure too low or high (Section-11.0, p.11-12)
Contaminant sticking valve open
Water connected to overflow outlet (installation error)
Not Filling Blocked inlet elbow
Blocked solenoid filter
Water turned-off
Kinked inlet hose
Water pressure too low or high
Solenoid coil failed (Section-11.0, p.11-12)
Scaled-up Normal-Operating Probe (Sec-4.0, p.6)
Normal Operating Probe wire shorted out
Faulty element (See: Not Heating below)
Thermal Cut-out activated (Section-10.0, p.11)
No Draw Off Tap spring or washer fault (Section-12.0, p.12)

Over Boiling Temperature set too high (Section-6.0, p.7)
Faulty thermistor (Section-5.0, p.6 -7)
Faulty triac (Section-8.0, p.8)
Machine not filling (Section-11.0, p.11-12)
Machine scaled up (Section-13.0, p.12-13)
Not Heating Thermal cut-out switch tripped (Section-10.0, p.11)
Faulty element (Section-7.0, p.7-8)
Faulty triac (Section-8.0, p.8)
Faulty P.C.B. (Section-9.0, p.9-10)
Unsound connection on element or triac
P.C.B. Blown Steam (See over-boiling above) or water damage
Element blown (315mA fuse on P.C.B.)
Triac blown (Section-8.0, p.8)
Taste Problems Washing machines or dish washer on same feed
BLUE or RED hoses on same feed
Outside interference
Expired cartridge-filter on feed
Foreign body in boiler

15.0 - SERVICE WARNING MESSAGES (Not WA5)

SIMPLE WARNINGS:

MESSAGE MEANING AND POSSIBLE CAUSES:
CHECK WATER The boiler has not sensed any drop in temperature after opening the cold-water valve a number of times.

Most common cause: An interruption of the water supply. Check the stop valve and make sure there are no kinks in the hose or debris in the water inlet valve.
The message can also indicate that the incoming water pressure is low.
Switch boiler off at the mains and back on again to clear message and reset.
NO WATER Six minutes after the boiler was switched on, the circuit has not sensed water on the low-level probe. Check that there is a water supply to the boiler and make sure that there are no kinks in the hose and no debris in the water inlet valve.
PLEASE NOTE that in hard water areas this message can be caused by lime-scale (see message CLEAN PROBES below). Once you have rectified the water supply or cleaned the low-level probe, the boiler must be switched off at the mains and back on again to reset.
CLEAN PROBES
(+1 or +2) The boiler is fitted with five level sensing probes. These sensors use a small electric current and a circuit is made by the water. In some areas hard water acts as an insulator. When a sensor becomes insulated by lime-scale, it is no-longer able to detect the presence of water. The water level in the tank then rises to a different sensor and the CLEAN PROBES message will display. This will be followed by a number 1 or 2.
CLEAN PROBES-1 indicates that the low-level sensor and possibly the ECO sensor are coated in scale.
CLEAN PROBES-2 indicates that one of the top three sensors is coated in scale.

CRITICAL MESSAGES:

MESSAGE MEANING AND POSSIBLE CAUSES:
THERMISTOR O/C

The temperature sensor has been disconnected or is faulty.
HEAT/THERM FAIL This means that either the “over-boil” or “boil-dry” thermal safety cut-out switch has activated or the element has failed. Switch the boiler off at the mains and back on again in 10 minutes. If the “over-boil” cut-out has operated, the boiler will automatically reset itself and work as normal.
If the “boil-dry” safety cut-out has activated (check if reset button is pushed in) or the element has failed, the message will recur in about 1 hour.
OVERFILL This means that the boiler has sensed water on the fifth level sensor (highest probe). If a previous “CLEAN PROBES-1” message had been ignored, eventually the water level would rise to the “overfill” sensor and bring on the (CLEAN PROBES-2) message.
Clean the probes as described in Section-13.
If this does not resolve the fault, the boiler has overfilled. This may be caused by a faulty water inlet valve or very high or low incoming water pressure.
MAINS PCB COMS. FAIL This means there is an electrical communication problem between the main PCB and the display PCB.
In 80% of cases, this will be caused by a fault with the flying wire-lead which connects both circuit boards together. Check that the wires are tightly pushed into the JST connector plug and that the JST plug is pushed firmly into the PCB sockets on both circuit boards.
Switch boiler off at the wall and back-on again to clear fault message. If this does not clear the error message, the fault must be with one of the circuit boards.
If the boiler is working correctly (e.g. filling heating etc.), it is most likely that the fault is on the display PCB.

16.0 - EXPLODED ASSEMBLY DRAWING & KEY

Drawing Description
No.

1. XE870 main printed circuit board (all WM series)
- XE150B main printed circuit board (WA5 only)
2. Triac (used to switch power to the heater via a signal from PCB)
3. Element (each heater is rated @ 3.0KW)
4. Element washer (blue silicone rubber)
5. Tank Gasket
6. XE871 display printed circuit board
7. Level sensing probe
8. Hexagon nut (to secure level probes)
9. Spring (for holding plastic tap-surround – No: 10)
10. Grey plastic tap-surround (not WA5)
11. Grey plastic tap collar
12. Brass tank-to-tap adaptor
13. Chromed tap extension
14. Draw-off tap
15. Boil-dry thermal safety switch (set to break @ 120^C)
16. Brass mount (for safety switch above)
17. Over-boil thermal safety switch (set to break @ 90^C)
18. Brass ¼”bsp to 15mm push-fit adaptor
19. 15mm straight push-fit coupling
20. 15mm “T” push-fit coupling
21. 3/4” nut, tail & washer assembly (for attachment to water inlet valve)
22. Solenoid valve (cold water inlet)
23. Internal water feed pipe (grey silicone rubber)
24. Plastic back-cover box (to protect display circuit board)
25. Heavy-duty rubber overflow/vent tube
26. Plastic outer case (Note: some models have a stainless steel outer case)
27. Plastic display-window (sealed into case with “O” ring)

Note: Exploded drawing shows WM7. Other models in the series
may vary in size but are identical in construction.

The WA5 is also very similar but with an L.E.D. light instead of an
LCD display

Exploded Assembly Drawing Key

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