Euro Combi SX 20 MFFICE (GC No: 4711602)

A few weeks agao, I had a problem with my heating - cured by changing the expansion vessel and installing a new PRV which was leaking (causing the pressure to drop). Heating & hot water were both working wonderfully well, until yesterday morning when I turned the hot water tap on ..... ghastly noises from the boiler and a rapid increase in temperature - causing the overheat cut-out to kick in. The temperature goes up to 140degC. When it cools down, I press the reset button & the boiler fires up, and the heating functions normally.

As soon as I try the hot water - the same thing happens again.

My gut feeling says it's the diverter valve - but any suggestions (or confirmation of my diagnosis!!) would be much appreciated.

Many thanks

Rob

Rob McKay, April 2009

THE MOST COMMON PROBLEM WITH THIS DESIGN IS THE DIVERTER VALVE DIAPHRAM. THIS GOES FAULTY EVERY 2-3 YEARS AS THE RUBBER IS UNDER CONSTANT STRESS. THE SECOND MOST COMMON FAULT IS THE PUMP WHICH YOU CAN OFTEN GET REWORKING BY HITTING IT WITH THE WOODEN HANDLE OF A HAMMER. £10 is cost of new diaphram rubber valve.

engdes, May 2009

Gaz - Thanks for the thought - but the pump is OK, as the heating is working fine. Both temp & water pressure remain constant - it's only the hot water, so the pump is not involved.

Rob

Rob McKay, April 2009

I would check the pump.if making loud noises and rapid temp rise sounds like it may be siezed

gaz, April 2009