Central Heating

[under pressure]

I have a simple problem and think I might know the answer so I am really looking for confirmation.

Even with my stat turned right down if my boiler starts to heat hot water then my radiators still get hot. This is the same even if I switch my boiler over to hot water only.

Can I assume that the motorised valve is jammed and is the cause of the problem ?

 

[Agile]

That seems most likely but there can be other causes!

Tony

 

[didgeradoo4719]

You don't say which make/type of boiler you have, but it could be the water to water heat exchanger that is faulty and would have to be replaced. If you have the manual for your boiler it should tell you how to do it. I replaced mine as I had the same problem.

 

[under pressure]

The boiler is a Myson Apollo with a string of numbers after it 15/30/. 30/50. 40 and 50/65 so it must be one of them lol

 

[45yearsagasman]

You don't say which make/type of boiler you have, but it could be the water to water heat exchanger that is faulty and would have to be replaced. If you have the manual for your boiler it should tell you how to do it. I replaced mine as I had the same problem.

Very unlikely to be a plate heat exch.If it was a combi (which it isn't)then those symptoms would point to diverter valve.

 

[under pressure]

So the most likely thing is the motorised valve then ?

The system is about 25 years old and I do live in a hard water area which as an electrician I know can mess the valves up

 

[45yearsagasman]

Yes its most likely to be a motorised valve passing.Its a pity that when people post with a problem with heating systems there is not a better description of the system controls as it makes for a better diagnosis.

 

[under pressure]

To be honest the controls are all pretty basic. The progammer is part of the boiler and the only other parts are a room stat, a tank stat, a pump and a motorised valve.

The only odd thing is the pilot light seems to go out when the bottom cover is on the boiler if you leave the bottom cover off it stays on ?

Odd to say the least lol

 

[Whitespirit66]

Hard water isn't really a major problem for motorised valves, as your rad and hw primaries/flow & return doesn't have fresh water constantly being added to it. Once the water in this circuit has given up the calcium carbonate that it contains, that should be it until you drain down and refill.

Motorised valves normally fail through wear and tear. Its usually, synchron motors, microswitches and the rubber ball inside the valve that give problems.

If you're replacing, fitting a Honeywell should give many years of service. You may also be able to replace parts in your existing valve.

 

[simond]

The only odd thing is the pilot light seems to go out when the bottom cover is on the boiler if you leave the bottom cover off it stays on ?

Turn it off and get an RGI in. This could be nasty.

 

[under pressure]

Thanks for the advice and I might well do that I have changed a few parts in it before so I am not a total idiot but I am a bit baffled that it starts immediately every time.

 

[expertgasman]

The only odd thing is the pilot light seems to go out when the bottom cover is on the boiler if you leave the bottom cover off it stays on ?

Turn it off and get an RGI in. This could be nasty.

Could be nasty, but more likely a loose connection - thermocouple nut perhaps.