WATER BOILERS to FEB 2006 (WA3, WA7.5 and WA15)

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“WA” SERIES SERVICE MANUAL (NOT WA5)

ISSUE: 1- Dated: August 2006
WATER BOILER BOTH STAINLESS STEEL AND PLASTIC CASED

CONTENTS
Principle of Operation.
1.0 Technical Specifications
2.0 The Tank.
3.0 The Thermistor.
4.0 The Potentiometer.
5.0 The Heating Element(s).
6.0 The Triac.
7.0 The P.C.B.’s
8.0 The Solenoid Valve.
9.0 The Draw Off Tap.
10.0 De-scaling.
11.0 Faultfinding.
12.0 Service Warning Codes.
13.0 Exploded assembly drawing key
14.0 Exploded Drawing & Wiring Diagrams
15.0 Appendix 1
16.0 Appendix 2

INTRODUCTION:

The WA series of wall mounted water boilers were introduced in late 1996 to complement the highly successful range of counter top models. This manual has been designed to be a guide for service engineers. It includes descriptions of how to replace all serviceable parts, exploded drawings of a complete WA 3, wiring diagrams and many sub-assemblies.
All models of wall boiler are similar in construction, but vary in size.

PRINCIPLE OF OPERATION:

On switching on, the machine first checks for water at the bottom probe. If no water is sensed at the probe, the solenoid is energised. If no water is detected after approximately 4 ½ minutes the solenoid switches off and the red service light flashes 6 times. 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 ready LED illuminates and 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 top probe and specified
temperature is reached.
When the boiler has reached the top probe and the correct temperature, it goes into ‘idle’ mode. The heating element is pulsed periodically to maintain temperature.

1.0 TECHNICAL SPECIFICATIONS:

WA 3 (WA3SS)

Voltage: 220-240V single-phase 50Hz
Supply: AC
Rated Input: 3.0kW
Fill Type: Automatic Fill
Recovery per Minute: 0.5 Litres (3KW)
Rapid Draw-off: 12.5 litres (21 pints)
Heat-up time: 33 minutes (from cold to full capacity)
Height: 420mm (440mm)
Width: 320mm (307mm)
Depth: 200mm (plus 80mm for tap protrusion)
Avg. Power Consumption: 0.1 (kw/hour - standby)

WA 7.5 (WA 7.5SS)

Voltage: 220-240V single-phase 50Hz
Supply: AC
Rated Input: 3.0kW
Fill Type: Automatic Fill
Recovery per Minute: 0.5 Litres (3KW)
Rapid Draw-off: 10 litres
Heat-up time: 20 minutes (from cold to full capacity)
Height: 465mm (487mm)
Width: 335mm (230mm)
Depth: 225mm (plus 80mm for tap protrusion)
Avg. Power Consumption: 0.1 (kw/hour - standby)

WA 15 ( 6kw)

Voltage: 220-240V single-phase 50Hz
Supply: AC
Rated Input: 3.0KW (6.0kW)
Fill Type: Automatic Fill
Recovery per Minute: 1.0 Litre
Rapid Draw-off:
Heat-up time: 11 minutes (from cold to full capacity)
Height: 515mm
Width: 350mm
Depth: 275mm (plus 80mm for tap protrusion)
Avg. Power Consumption: 0.1 (kw/hour - standby)

2.0 THE TANK:

The tank lid is secured using M4 stainless steel screws. The lid is sealed with a rubber gasket. Silicone sealant secures the gasket to the tank, and the lid is sealed with silicone grease. There are four level sensing probes inside the tank.* Only the bottom probe and the top probe are used in normal operation, the other two are overfill warning probes.
* Only two in a WA5

3.0 THE THERMISTOR:

IMPORTANT : The position of the thermistor on the tank is level with the top leg of the element.
To remove the old thermistor, chip it off using the tip of a screwdriver.
To ensure that the new thermister 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 thermister 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.

4.0 THE POTENTIOMETER:

The potentiometer controls the temperature of the water. By turning the control knob the temperature can be increased or decreased. This control is easily accessible, and if it is adjusted inadvertently could result in the safety cut-out switching the machine off.
(Not WA5)
The WA5 potentiometer is mounted on the P.C.B. and can be adjusted with an electrical screwdriver.

5.0 THE HEATING ELEMENTS:

The heating elements are made from an Incoloy material. They are sealed by two blue silicone washers and held into the tank by two ¼” lock-nuts.
The element should have a resistance of between 19 and 20 ohms and 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.

6.0 THE TRIAC:

The triac is a device 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 panel using heat-sink compound between the surface of the triac and the panel.
There are 2 types of triac’s used on the wall boilers. The XE851 for the 3kw models and the XE854 for the 6kw 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 pipe, the safety cut-out will detect a rise in temperature and
switch the machine (3kw) or power to the elements (6kw) off. If the triac has failed in the closed position there will be continuity between the live element terminal and the live into the triac (grey wire 3kw & red wire 6kw).

7.0 THE PCBs:
The Trip P.C.B. WA3, WA7.5, WA15-3 & WA15-6.

There are two P.C.B.’s on the wall boiler (not WA5). The first (XE856/3N for 3kw and XE856/6N for 6kw) is the over temperature trip P.C.B. This detects any rise in temperature in the overflow pipe, via a moxie sensor, and disconnects the power supply from the main P.C.B. and triac. If this happens the red board-mounted L.E.D. will illuminate. To re-set, switch machine off and allow to cool down (approx. 5 minutes), the trip P.C.B. will automatically re-set.
NOTE: Machines after July 2002 have thermal cut-outs not a trip board – see
Appendix 2

The Main P.C.B. WA3, WA7.5, WA15-3 & WA15-6.

This P.C.B. (XE850) controls the main functions of the machine, monitoring the water level, water temperature, water supply etc. If a fault is detected the user is warned via the service or ready L.E.D. Some faults render the machine inoperative whilst others will only give warning flashes (See chart on page 10 for details).
The XE850 P.C.B. can be configured for use on either 3 or 6kw machine applications. The configuration is determined by the inclusion (6kw) or exclusion (3kw) of a small jumper plug. This connector tells the microprocessor how much water to put into the machine in one pulse.
* Refer to wiring diagram for connections *

8.0 THE SOLENOID VALVE:

Disconnect machine from electrical supply before replacing. The valve can operate between 2 bar (28 psi) and 7 bar (100 psi) 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. blown fuses or electronic components.
NOTE: Always check solenoid coil before replacing P.C.B.

9.0 THE 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.

10.0 DESCALING (including cleaning probes):

NOTE: It is possible to remove the case on the WA3SS & WA7.5SS without draining
the water and removing the tap.
Disconnect the machine from the power supply.
Drain the water with draw off tap.
Remove draw off tap using 28mm open-ended spanner.
Unscrew cover screws (top and bottom of case) and remove case and flying lead from L.E.D.’s.
Remove tank lid and baffle plates.
Syphon remaining water out or unscrew drain plug where applicable.
Remove as much loose scale as possible by hand. Any hard scale coating the level sensing probes and holders, should be cleaned off using a non-metallic scouring pad.
Use a good de-scaler such as “Renegite” (Part No. ACC303) to remove hard scale deposits. Mix 2-3 packets in hot water and pour into tank (do not forget to replace drain plug). Leave for approximately 20 minutes.
Flush tank out with water, ensuring that all traces of de-scaler are removed before re-assembly.

11.0 - FAULT FINDING:

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

MACHINE SYMPTOM - Dead
CAUSE:
Thermal cut-out tripped (3kw) - See over boiling
Safety P.C.B. tripped (not WA5)
P.C.B. faulty - (250mA fuse or transformer)
No mains input (installation or outside interference fault)
Unsound terminal connection
Blown fuse in plug (3kw)
Bad connection in plug (mains lead fault)

MACHINE SYMPTOM - L.E.Ds Flashing
CAUSE:
See chart below

MACHINE SYMPTOM - Overfilling
CAUSE:
Water pressure too low or high
Contaminant sticking valve open
Water connected to overflow outlet (installation problem)

MACHINE SYMPTOM - Not Filling
CAUSE:
Blocked inlet elbow
Blocked solenoid filter
Water turned off
Kinked inlet hose
Water pressure too low or high
Solenoid coil failed (See page 6)
Scaled up top probe
Top probe wire shorted out
Faulty element (See not heating)

MACHINE SYMPTOM - No Draw Off
CAUSE:
Tap spring or washer fault

MACHINE SYMPTOM - Over Boiling
CAUSE:
Potentiometer set too high or faulty (See page 4)
Faulty thermistor (See page 4)
Faulty triac (See page 5)
Machine not filling (See Page 8)
Machine scaled up (See page 7)
Faulty element (See page 4)

MACHINE SYMPTOM - Not Heating
CAUSE:
Thermal cut-out tripped (See page 6)
Potentiometer set too low (See page 4)
Faulty element
Faulty traic
Faulty P.C.B.
Unsound connection on element or triac

MACHINE SYMPTOM - P.C.B. Blown
CAUSE:
Steam (See over boiling) or water damage
Element blown (fuse on board)
Triac blown (See page 56)
Solenoid coil blown (See page 6)

MACHINE SYMPTOM - Taste Problems
CAUSE:
Washing machines or dish washer on same feed
BLUE or RED hoses on same feed
Outside interference
Expired filter on feed
Foreign body in boiler

12.0 - SERVICE WARNING MESSAGES:

WA 3, WA 7.5, WA 15-3 & WA 15-6
All machines:
The Ready light is flickering. The water pressure on the premises is low, the water supply has been turned off or there is a scale build up. The light will stop when the water has returned to normal.

16.0 - EXPLODED ASSEMBLY DRAWING & KEY

Drawing Description
No.
1 P.C.B. - Main
2 P.C.B. - Over-temperature trip (not WA5)
3 Triac
4 Heating element
5 Heating element washers
6 Tank gasket
7 L.E.D. assembly
8 Probe assembly
9 Probe nut (chrome)
10 Internal silicone rubber water feed tube
11 Overflow pipe - semi-rigid polyethylene
12 Thermistor (temperature control)
13 Potentiometer (temperature adjuster) - WA 5 on main P.C.B.
14 Water inlet blanking bung
15 Water inlet push-fit “T” coupling
16 Solenoid valve
17 ¼”BSP to push-fit adapter
18 15mm push-fit overflow coupling
19 Drain plug
20 Plastic tap collar
21 Complete draw-off tap
22 Tap backing washer - yellow
23 90^C thermal cut-out (WA5), Moxie sensor c/w flying leads & JST plug (WA3, WA 7.5 & WA15)
24 Stainless steel sensor mount

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15.0 APPENDIX 1

Elements
Boil Dry Element Protection
All machines from March 2002 have boil dry protection on the elements.

This consists of a new type element (Part No: XEN175) and 115^ thermal cut-out (Part No: XETR5). This element looks similar to the existing one, but has a brass mount brazed onto it. This is where the thermal cut-out is mounted. This cut-out will trip if the water level falls below the element to prevent it overheating.
See table below for Serial No’s.

* Boil-dry element protection

16.0 APPENDIX 2

Trip PCB
WA3, WA7.5, WA15-3, WA15-6
All machines form August 2002 will have thermal cut-outs on the overflow. Should the temperature be set to high, steam or boiling water could discharge through the overflow pipe. In the event of this happening, the over-boil thermal cut-out (set at 90^) will temporarily switch the heater off. If this occurs and the boiler is not isolated from the power supply, it will automatically reset once it has cooled (approximately 20 minutes), and repeat the over-boil cut-out cycle (not WA5). It is recommended that you adjust the temperature by tuning the knob anti-clockwise. After this adjustment, if the boiler continues to over-boil, see Fault Finding section ‘Over Boiling’ or contact Instanta service department for advice.