Boiler Issues - HELP!!!

ash t · World Chat Champion Joined: 15 Dec 2004 Karma :

Hi All,

Im having problems with my combi boiler.

Heating working perfectly fine, however hot water is a different matter.

Sometimes, hot water works fine....tap on, boiler kicks straight in, however sometimes, the boiler doesnt kick in and the water is ice cold (Lukewarm at first if heating is on).

I know its not broken because it works off and on.

Any ideas on what it could be, and how much its going to hurt my pocket???

Thanks!
Ash
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The Artist · Super Spammer Joined: 06 Jan 2008 Karma :

We had loads of issues with our boilers and I ended up doing a lot of research on combi boilers.

Most likely thing I would say is a valve somewhere is stuck/broken and needs replacing. Shouldn't cost too much but hiring a guy is the expensive bit.

TBH what you have is not a major issue. It is major when you have not hot water at all Laughing

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

Sounds similar to the issue we had with the diverter valve. Not massively expensive. Ours was the other way though, with no heating unless you played with a hot water tap.

All the best

Keith
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yen_powell · World Chat Champion Joined: 22 Jun 2008 Karma :

I agree, sounds like your three way valve is sticking. Look for a t shaped brass valve with a little plastic box stuck on the front. It controls where the water goes from your boiler, to the hot water, the radiators or both. Mine is in the airing cupboard near the hot water tank and pump.

Remove the plastic box (held on with a couple of screws) and turn the valve back n forth with a spanner or pliers to free it off and move the limescale about inside it. Replace the plastic box and see if it makes a difference.

I'm on my 3rd valve and 2nd electric switch (the plastic box) in 10 years now. Turning your heating on a few times over the summer helps keep it moving freely.
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Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

The one in ours was built into the boiler.

Piccy of it here:-

https://www.alfa-pages.co.uk/TempPicture/DiverterValve.jpg

There is a rod through the hole in the middle (pokes out of the bottom) and it is this that was sticking.

All the best

Keith
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Al · World Chat Champion Joined: 26 Feb 2006 Karma :

It does sound like the diverter valve inside the boiler casing that Keith is talking about.
If the pin isn't moving when you turn on the hot water the diaphragm washer inside the valve is more then likely spit. If the pin still moves then the micro switch that the pin activates is probably knackered as this is what tells the boiler to fire up.
The valve isn't expensive but depending where its located in the boiler it can be awkward to replace.
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owdamer · World Chat Champion Joined: 06 Oct 2004 Karma :

Sounds like the divertor valve to me as well. We had to have ours replaced in a potterton boiler a few years ago. Thing it was cost about £100 inc fitting.
In a potterton its a pig of a job as its hidden behind everything so theres no room to get in. Our boiler packed up 3 years after the divertor was changed and it looks like the valve had started leaking which left a pcb imersed in water. (great design eh). Following that we had a new boiler fitted, a viessman. Wouldn't have another potterton.

ash t · World Chat Champion Joined: 15 Dec 2004 Karma :

Thanks for the replies.

Still having problems. Hot water is perfect first thing in a morning when the heating hasnt been on. It seems like its not working when the heating is on/has been on prior to wanting hot water.

The manual to the boiler shows that the 3 way valve is easily accessible, its literally looking at you when you take off the cover to the boiler itself.

Im thinking it may need a good clean as its working fine when it works.
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Al · World Chat Champion Joined: 26 Feb 2006 Karma :

Its still sounds like a small spit or hole in the diaphragm washer inside the diverter valve.
The central heating water is heated in the boiler and then sent through the diverter valve and directed round your heating system to your rads.
A combi always gives priority to hot water demand, so when you switch on the hot tap, mains water is sent through another part of the diverter valve where the pressure causes the valve to change position. This then diverts the water that would be pumped around your heating system to a second heat exchanger which heats the mains water thats just entered the boiler giving you hot water from your tap.
If you can easily see the diverter valve try turning the hot water on and off and see if the pin moves.
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kitty kat · World Chat Champion Joined: 20 Jun 2007 Karma :

try turning control in the shower to cold, if when you have done that then water from tap is hot it is the non-return valve in the shower at fault. If that has no effect, try the diverter valve in the boiler.
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