Hot water intermittent

[richdoc]

Hi,

I have been having a problem with my combi boiler for a while now, and wondered if anyone here could shed any light on pssible causes.

Its a Saunier Duval Isofast Condens F35e, gas combi boiler.
The problem is its difficult to get any hot water out of it, it happily dispenses loads of tepid water but rarely gets hot. I have found a way to get it to work, which involves running the tap for a minute at a low speed, then turning it off, wait until the boiler cuts out then start the tap again. If I do this 3 or 4 times the water eventually gets up to the correct temp. Obviously wastes a lot of water too though.
We have had the heat exchanger removed and cleaned out, as best they can be, we have also had the boiler flushed. Prior to this work being done the boiler was not outputting any hot water at all, just tepid water.

Anyone have any ideas??

Thanks

 

[ChrisR]

If you turn the HW on and it runs tepid, does the CH flow pipe get hot? It shouldn't.

 

[richdoc]

If you turn the HW on and it runs tepid, does the CH flow pipe get hot? It shouldn't.

Thanks Chris, I will check tonight and see.

 

[richdoc]

If you turn the HW on and it runs tepid, does the CH flow pipe get hot? It shouldn't.

OK, I have checked the boiler and the CH pipe does indeed get hot! What does that mean?

UPDATE: Given the clue that ChrisR gave me (I hadnt noticed the rads where getting hot when the hot tap ran) I had another look on the forum. Now I am thinking I have a knackered diverter valve.

Looks like I need to get it replaced, can anyone tell me if this will be expensive?

Thanks again