ravenheat

[carltovey]

I have a ravenheat condensing boiler, when trying to get hot water the unit fires up for a few seconds then goes off then comes on and takes ages for it to kick in, if heating is turned on the water stays on and heats up.
Any ideas? been told it is the diverter valve and the diaphram can not be changed on its own and needs a new unit

 

[Slugbabydotcom]

Which model is it?

How old is it?

How many lights on the front 2 or 3?

I'm guessing its a pre September 2005 HE/CSI 85 T with 3 lights in which case you will probably need a new CH thermistor. NOT the DHW thermistor as you might expect

 

[carltovey]

CSI85 or CSI 85T
the "registered gas guy has taken the service manual to price up a divert valve"
2 lights on front
couple of years old no more than 3

 

[Slugbabydotcom]

Probably the fan modulation board then unless its the CSI 85B which doesn't have one. Very common fault.
Diaphragm can be changed. just use one out of a worcester. they cost about £40.
Cheaper ones can be got for around £15 but they are not genuine giannoni parts. Pay your money and take your chance with them.

The flue needs checking to make sure theres no trifids in it or it hasnt been cajoled.

Cant give you any more now. I just been called out but that should do for starters