Boiler issues heating hot water

[mayfel]

Hi!

I have a Ravenheat CSI/HE range combi. Recently it started running cold water after a few minutes, and then back to warm for a bit, then cold again etc. Even more recently it sometimes won't even start running warm at all.

The heating has been off for months (summer) but I tried turning the heating on (timer and thermostat) and then running the hot water and there's no problem! Nice hot water. The boiler doesn't actually do any central heating in the time the water is running (presumably not powerful enough to do both).

Do these symptoms help point to what the problem might be?

Cheers!

 

[bellairaphon]

Divertor valve by the sounds of it

 

[45yearsagasman]

Restricted plate heat exchanger by the sound of it. Combis, by design only provide one service at a time.

 

[mayfel]

Many thanks for the replies you two! I've been away so couldn't reply till now though.

Before I have a little dismantle I have a few more observations I was hoping would maybe clarify the situation further:

- There is now never any hot water (boiler not lighting) when I run the hot taps with heating off.
- Still works if central heating is on - normal pressure and constant hot water flow.

* When I turn on hot water tap the diverter pushes out onto the microswitch (but the boiler doesn't attempt to ignite)
* BUT if I leave the hot tap off and hold down the microswitch manually then the boiler ignites

Does this help narrow it down at all?

Many thanks again!