CH pump runs 24/7

[Jim]

Had a biggish rennovation project done that involved replacing an old (Potterton Netaheat) boiler with a new Vaillant Ecomax Pro boiler - 2 months ago. Incidentally, I have what I understand to be an open-vented "S" plan system with two motorised valves. I retained the original 2 channel programmer. The plumber (from Eastern Europe and Corgi registered) who installed the boiler (on sub-contract from the builder) never inspired me with much confidence. Maybe it's because of recent stories about one-legged Romanian roofers :-).

Anyway, there's been a series of problems ever since. The boiler is understood to be 100% OK - as confirmed by the Vaillant engineeer who has visied twice.

The symptoms are:-

1. Recently, the circulating pump (adjacent to the HW cylinder) appears to be running continuously - even when the programmmer is not calling for heat. It is set to operate to provide central heating and hot water during two time periods per day. The radiators warm up and cool down exactly in accordance with the programmer schedule. The boiler fires up every 3 or 4 minutes and when the boier display reaches 68 degrees it stops heating. The temperature in the display drops slowly to around 45 and then the burner starts up again. This cycle carries on 24/7 - even when the programmer is not in an active period. Presumably it is trying to heat the HW cylinder as the radiators stay cold when the programmmer is not in an active period. This problem has emerged only recently.

2.If I over-ride the programmer during an active period ie to shut off the heat, then the boiler stops OK but will not restart later on theschedule. It registers an "overheat" situation and has to be reset by taking off two cover plates and pressing the reset button. I believe this is because the pump stops and hence the circulations stops - causing the combustion chamber to trigger an over-heat situation.

Factoids:- After the boiler was first installed, there was no display on the boiler when the programmer was inactive. I complained about this and the builder brought in an electrician who connected a permanent mains supply to give a fulltime display. We thought we were over all the problems the problems then but a few weeks later problem 1. above emerged.

The questions that spring to mind are:-

1. Have I recently developed a a stuck motorised valve?
2. Did the plumber wire up the programmer correctly to the boiler?
3. What can I do to isolate/identify the problem further?
4. Where can I get a competent boiler installer cum plumber in South London that can check this out.

JG

[BigWallop]

It sounds as though it's all wired wrong, so get the electrician back to do it right.

[Dave Plowman (News)]

Sounds like you need a competent electrician. Boiler installers freqently are anything but.

[logized]

There must be some serious wiring errors. It would be a good idea if you provide the electrician with the data sheets for all your controls and boiler and ask that he fix it and make a circuit diagram of the installation for future reference.

Dave

[Set Square]

It sounds like you need an electrician who understands heating systems. It needs to be wired as per S-Plan in

except that the boiler almost certainly has 3 'live' terminals - a permanent live, a switched live (to be connected as per L in the diagram) and a pump feed. The pump's live needs to be fed from the boiler's pump feed terminal. That way, the boiler will keep the pump running for a bit after it has stopped firing, to prevent overheating.

There must also be (in the plumbing rather than electrics) a by-pass circuit to give the water somewhere to go during the pump over-run phase when both zone valves are closed. Have you got one?

Unless you've got a frost stat which over-rides the timer, neither the boiler nor the pump should run when the timers are off.

[The Natural Philosopher]

Could be. I'd say thh DHW valve is stuck uif te radiators are beahving normally. You'd epexct short cycling, and very hot DHW if that was teh case.

Who knows. It's an issue. It may be that in order to get the display on, he has inadvertantly also made the boiler and pump on all the time.

On my boiler, short of cutting interanl wires, the (integral) pump will run all the time if the boiler has power.

You say this problem was not present when the 'permanent LCD display' was activated? Are you sure?

Check where the water is running. I assume the rads don't get hot on the short cycling, so check if the water tank and its primary are contunously hot, and also check phsyically the motorised DHW valve to see if the microswitch is permanently stuck on. Also arrange to vbe near that valve and switch off teh whole bolier ekectricity. See if you can hear or see it moving.

You are it IMHO. :-)

I see two basic explanations - DHW motorised valve stuck on, or the boiler is not being controlled by the motorised valves properly, and is in fact hard wired to be permanently on.

[Andy]

I think there is a problem with the pump over-run as set square mentioned, there is a permanent live feed to the boiler which is designed to run the pump even if the timer is off. Basically to get rid of the heat from the heat exchanger, that's why you overheat when you over ride the controls. I`m not sure on the Vaillant Ecomax but there are two main methods of controlling the over run. The first is off the board, usually off a relay and the second is off the boiler thermostat. Is there anything in the user guide that helps?

Andy

[Jim]

Many thanks to you all for the prompt and consistant responses.

I can now go suitably prepared to tomorrows site meeting which hopefully will be the last one.

Cheers JG

[IMM]

He needs a heating engineer. Electricians know nothing of heating system operation, unless he specialises in heating control wiring and is employed by a heating contractor.

[Lurch]

On Thu, 16 Dec 2004 11:39:30 -0000, "IMM" strung together this:

Why do you bother? Fuck off and die.

[IMM]

Your ISP may get to know of your insults.

[BigWallop]

LOL !!!!

[Lurch]

On Thu, 16 Dec 2004 12:35:03 -0000, "IMM" strung together this:

Oh no, what will I do.

[Dave Plowman (News)]

Which proves beyond any reasonable doubt that you're no heating engineer, given your lack of knowledge of anything electrical.

FWIW, a competent electrician will have no problems with any domestic heating control gear wiring. They are simplicity itself for a competent electrician. Difficult for a 'heating engineer' to understand this, I'll grant you.

[IMM]

You will know when they contact you.

[IMM]

Imbecile you are wrong.

My knowledge of electrical matters is excellent and above excellent.

I have told you before. Don't give advice on topics you know sweet FA about.

[Lurch]

On Thu, 16 Dec 2004 13:53:04 -0000, "IMM" strung together this:

Yeah, right.

[Lurch]

On Thu, 16 Dec 2004 13:58:39 -0000, "IMM" strung together this:

You are total f****it.

[BigWallop]

If a fly by night sparks can't wire up controls for a simple heating system, then he is not a qualified electrician. The electrical supply system for central heating is simplicity itself to a good electrician. It contains a wiring scheme for simple switching systems that any good electrician could work out in his sleep. A good plumber might have some knowledge of how the wiring works, but any good electrician should know exactly how and where things should go without problems.

[Dave Plowman (News)]

Absolutely. Of course all IMMs 'trade' pals use PP drills, so aren't even worthy of the name 'cowboy'.

Still, the more he goes on about it needing a 'specialist' to wire up domestic heating controls, the more it shows he has no practical experience in such things.