MANUAL FILL WATER BOILER

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Introduction :

The Manual Fill water boiler (MF25) was introduced in August 2000 to compliment the economy range of water boilers.
This manual has been designed to be a guide for service engineers. It includes descriptions of all serviceable parts and an exploded drawing of a complete machine and a wiring diagram.

Principle of Operation :

The boiler must be manually primed with water. Once switched on the L.E.D. will illuminate red and the heating element will start to heat the water. When the water has reached approximately 70^C the L.E.D. will change to amber, and when the water reaches approximately 90^C the L.E.D. will change to green. When cold water is added and the temperature reduced, the L.E.D. will illuminate accordingly and the heating element will switch on.

Technical Specifications :

Size (mm) :

Height : 720
Diameter : 330

Electrical Loading (kw) :

MF25 : 3

Heat Up From Cold (Litres/mins) :

MF25 : 0.5

Average Standby Power Consumption (kw/hour) :

MF25 : 0.23

The Tank :

The tank is rolled from stainless steel and seam welded. The lid is spun and swaged to fit the top of the tank.

The Thermistor :

See Drawing D35 (XE853)

The thermistor is situated on the bottom of the tank.
To remove the old thermistor, chip it off using the tip of 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

The Potentiometer :

The board mounted potentiometer controls the temperature of the water and is factory set between 96-98^C. If adjustment is required, access can be gained by removing the black bung above the cable entrance. Use a torch to illuminate the access hole and a small electrical screwdriver to adjust the potentiometer.
Turn clockwise to increase.

The Heating Element :

The heating element is made from an Incoloy material. It is sealed by a rubber washer and P.T.F.E. tape.
The element should have a resistance of between 19 and 20 ohms and will draw between 11 and 12 amps.
If the element has blown it will have an open circuit. To test this use a simple PAT test.

The Triac :

See Drawing D35

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.
The triac used on the MF25 boiler is the XE851.

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).

Main P.C.B. :

This P.C.B. (XE250) controls the main functions of the machine, monitoring the water temperature. If a fault is detected the user is warned via the L.E.D.

* Refer to wiring diagram for connections *

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.

De-scaling :

• Disconnect the machine from the power supply.
• Remove the lid
• Remove as much loose scale as possible by hand.
• Use a good de-scaler such as “Renegite” (Part No. ACC303) to remove hard scale deposits. Mix 3-4 packets in hot water and pour into tank. Leave for approximately 20 minutes.
• Flush tank out with water, ensuring that all traces of de-scaler are removed before
  re-assembly.
  

Service Warning Codes :

The boiler has a limited fault diagnosis program built-in to the P.C.B. This will flash the L.E.D. if certain faults occur.

Fault Finding :

Exploded Assembly Drawing Key :
(click to view drawing)