Diverter valve problem fixed but now another problem.

[dave]

I have a Halstead Wickes Combi 2000 boiler. A month ago I was only getting domestic hot water when the central heating was on, I traced this to a perished Diverter valve diaphram and replaced the complete valve and everything was fine, I had hot water back. A month later and now its gone again? But different symptoms this time. If I turn on the domestic hot water the pin on the diverter valve moves up as it should and operates the micro switches OK and the burners come on. But the heating appears to go to the central heating circuit and the radiators get nice and hot, the domestic hot water never gets above luke warm. The diverter valve appears to be moving but not diverting, any help please? I'm confused.

I don't know if this is relevant but when I open up the Automatic Air Vent bleed nothing comes out no water or air.

Thanks Dave

[Christian McArdle]

It may well be relevent. Are you sure you've topped up the system to enough pressure? What does the pressure gauge read when cold? It should normally be at about 1-1.5 bar. If not, top it up until it is. Then fire up the boiler and wait a few minutes. If the pressure goes about 2-2.5 bar, then you have an inadequete or broken pressure vessel. If the cold pressure steadily goes down in less time than several months, then you have a leak or dodgy pressure relief valve.

Christian.

[Christian McArdle]

I meant "above", not "about". Basically, the pressure rise when heated should be less than 1 bar. The lower the better.

Christian.

[dave]

Thanks Christian for the fast response. Yes I did notice yesterday the pressure had dropped, I topped it up and I see it has gone down again, and I have just looked outside and there is a slow drip from the pressure relief valve pipe. Hopefully it just hasn't seated properly, but it's an easy fix unlike the expansion tank. I topped back up to 1.5bar and ran the hot water it creeps up to 2.4bar and seems to hold there. The hot water gets warmer but not as hot as it should be and not as hot as the central heating radiators, it seems the diverter valve is still not diverting most of the water? Shouldn't the system operate normally while the pressure has been topped back up to 1.5bar ? could there be another problem

Thanks Dave

[Christian McArdle]

Turn the heating off. Let everything cool down. Now run a hot tap with the CH still off. Do the rads heat up?

Christian.

[dave]

Yes I have had the central heating off during all of these tests and the rads get hot as if it was on.

Dave

[Christian McArdle]

Sounds like the diverter again, I'm afraid...

Christian.

[dave]

Yes that was my feeling, everything seems to point to the diverter valve. The diaphram is moving but maybe the vale at the bottom is sticking, I'll take it out and have a look at it.

Thanks for your help

Dave

[Ed Sirett]

Good that's how it's meant to be, provided there is pressure in the system.

My guess is that the secondary heat exchanger has got nearly blocked this is forceing the water through the rad circuit/ bypass / anywhere but where you want. How old is the unit?

[Ed Sirett]

Could well be stuck due to black bits.

[dave]

Hi Ed The water is very hard down hear in Hampshire and I was wondering if bits of limescale are a possibility. the boiler is about 7 years old. Is there any way of distinguishing between a blockage in the hot water heat exchanger and a blockage in the diverter valve? thanks Dave

[Ed Sirett]

I take it that you originally replaced the diaphragm which is the bit that moves the diverter valve. The diverter valve may have springs in it which mean that even if the pin moves the gubbins aren't.

I would resign yourself to draining, overhauling, flushing out and descaling bit as needed.

[dave]

Ed I replaced the complete diverter valve, but I guess it could still have something blocking it. Yes I think I must draindown and remove the diverter and probably the heat exchanger to inspect and descale, at least I seem to have identified the problem to two options.

Thanks all Dave

[dave]

I did replace the complete diverter valve but I guess it could still be blocked. Yes I think I will need to take the diverter valve and probably the secondary heat exchanger out and have a look at them.

Thanks all Dave