Central Heating : Wiring Query

[John Pearson]

I have scanned through the numerous queries regarding problems with Central Heating when the Hot Water part of the system is working fine (the problem I also have) and noticed that the majority of times replacing the motor sorts the problem.

I had a heating engineer out for 2 1/2 hours on Friday trying to find the cause of the problem and needless to say he thought the motor needed replacing but it is fine.

The question I had was what triggers the boiler to start up if the microswitch wire on the central heating motorised valve unit is deliberately capped off with a junction box?

The engineer and myself both looked for a stray wire to attach to the other side of the junction box to no avail.

Seems every issue I ever have with houses I own is a 'non-standard' setup.

Thanks in advance,

John

[Lurch]

In some instances the boiler is wired to come on with the valve, so in your case it could be that the brown, (motor live), could be connected with the boiler switch wire in the junction box. What type of system do you have, Y plan, S plan. When you say motor I assume you mean motorised valve motor, do you? It is unlikely that the wiring would just fall out with no trace of where it came from but some more info would help to diagnose a littlke further.

SJW

[John Pearson]

Not sure whether my system is Y or S plan but based on what the engineer said I would think it is Y plan.

The motor I mentioned is indeed the motorised valve motor.

I have a Potterton EP2002 control panel.

Really ought to know what make my boiler is but I can't remember.

Hopefully there is an engineer at home working on the problem as we speak, with some knowledge of the electrical side of central heating.

The engineer who came round on Friday said the on-call guy for the weekend wasn't qualified to work on gas systems (not Corgi registered) which I thought was particularly useful, not.

Thanks for your prompt response,

John

[Lurch]

Quite often it is the valve but I have come across instances of it being the cylinder stat. If you want to test it yourself try this. I could go into detail with the wiring I know people who do this all the time getting confused from time to time! Assuming you have a mid-position valve . Turn the cylinder stat down to minimum and turn the room stat up to call for heat. With CH on only on the programmer, the boiler and pump should fire and the pipe below the valve should become warm, the pipe off of port 'A' should be warm also. Feel about 6-8 inches back from the valve. Now turn the room stat down to minimum and turn HW on at the programmer, the boiler and pump should run and the pipe off of ports 'B' should become warm. Now turn the room stat up to call for heat, pipes at ports 'A' and 'B' should be warm.

If it's not doing this let us know what it's not doing, hopefully it'll be a "regular" fault and not something totally obscure! SJW

[ARWadsworth]

A failed stat / a stat turned up to the max temp /or stat not connected correctly to the tank cylinder stat may cause this fault. Is the boiler firing when your programmer is not calling for either HW or CH?

-- Adam

adamwadsworth@(REMOVETHIS)blueyonder.co.uk

[John Pearson]

Mystery solved.

Turns out that my heating system has 1 valve for water heating and 2 valves for central heating.

The central heating valves are located under a hatch in the understairs cupboard and upstairs in the front bedroom cupboard underneath the built in shelves (convenient I don't think).

The upstairs CH valve had a faulty motor (the cause behind 90% of CH problems where you get water heating but no room heating it seems to me) and once swapped every thing is now working correctly.

I'll have to leave some instructions as to where all these valves are for the next people who live in this bizarre house.

Thanks for all the advice,

John

[Christian McArdle]

Then it is probably S Plan Plus. The best system. Ensure you have programmable room thermostats in each zone. Then you can set different timings for the bedrooms vs the reception rooms. There's no need to heat the bedrooms during the day.

Christian.