no hot water, but ch is working

richard686

We have gas ch and hw, now that I have turned off the heating, I found that the hot water is not coming on.

First I checked the cylinder stat and it's on 'Call'.

Next I checked the HW diverter valve and I can see that moving between A and B when I open and close the cylinder stat.

There is no sign of boiler ignition or the pump running.

The boiler and pump work fine as the CH works fine.

We had hot water when the CH was on so the diverter valve must be working too (and I can see the motor operating).

Any ideas?

The system is a gravity combi.

MX5huggy

The system is a gravity combi.

No it's not a combi does not have cylinder.

richard686

MX5huggy wrote: »

No it's not a combi does not have cylinder.

yes got confused with the other house!
it's just a bog standard boiler.

richard686

Further investigation showed me that the HW demand is on from the programmer so that leaves the aux switch in the motorised valve.

I have live on the brown input and nothing on the orange return.... which goes to the boiler.

So probably a knackered microswitch or maybe the valve isn't quite reaching.

richard686

Interestingly, it looks to me like it's never worked! The cam that's supposed to operate the aux microswitch doesn't even get near it when the valve is fully open.

That explains why our hot water is always too hot!

richard686

Put a new microswitch in, all working fine now.

richard686

Ha, a Drayton motorised valve, what a POS!

It's sticking now so HW is still on all the time...

The spring return is so weak that the slightest friction in the valve means it sticks open.

£60 for a Drayton, £110 for a Honeywell, go figure.