Vaillant turbo cut-out problem

[notsohandyandy]

Once the boiler has been firing for some time (about 3 hours), it then stops firing, although the fan (?) keeps running. All the radiators get cold. It won't fire again until the whole system has been turned off (either manually or on the timer) for at least 30 mins.

Same problems last year - several fruitless visits from British Gas, who replaced various circuit boards, or seemed to think that we were making this problem up, or said things like all radiators in all rooms must be on at max all the time...

Boiler is a Vaillant Thermo compact VC GB 282 E - installed circa 1995

Any advice very gratefully received

 

[ChrisR]

An interesting problem! I can't think of anything- try posting on the plumbing-pages forum where there are more boiler engineers, or gas-news. I could only suggest a Vaillant engineer, if you can get one.

 

[notsohandyandy]

Once the boiler has been firing for some time (about 3 hours), it then stops firing, although the fan (?) keeps running. All the radiators get cold. It won't fire again until the whole system has been turned off (either manually or on the timer) for at least 30 mins.

Same problems last year - several fruitless visits from British Gas, who replaced various circuit boards, or seemed to think that we were making this problem up, or said things like all radiators in all rooms must be on at max all the time...

Boiler is a Vaillant Thermo compact VC GB 282 E - installed circa 1995

Any advice very gratefully received

 

[corgiman]

This sounds like the anticycle pcb has gone

This pcb stops the boiler firing up unnecessarily by making sure that the boiler does not fire up within a set period of time from the thermostat shutting down.

agree with chris get vaillant out to sort it.

 

[notsohandyandy]

We took your advice and called Vaillant. The saga continues - with Vaillant this time. A new pcb was fitted on Thursday but Friday evening the boiler cut out again, exactly as before. The Vaillant engineer this morning now says that he can do nothing until we get the boiler/timer re-wired. The boiler is currently wired so that power goes to the timer first, then to to the boiler. i.e. when the timer is off the red on-off rocker on the boiler is off. He says (and he is the first engineer to say this in 3 years of engineers) that it should be wired the other way round so that the power goes to the boiler then to the timer and back. Is this correct, and do you think it will it solve the 3 year old problem of the boiler cutting out intermittently? The boiler was installed about 8 years old. If you agree with him that this is the cause could you explain why you think it is the cause? Many thanks

Boiler is a Vaillant Thermo compact VC GB 282 E - installed circa 1995

 

[notsohandyandy]

and boiler cut out again about 2 hours later. Yippee!

 

[notsohandyandy]

Problems start-up again after nearly 2 months of good behaviour. Cut out after a few minutes this morning, after sharp overnight temperature drop, then fired when rocker switch on and temperature was at 0, then cut out after about 30 mins., then refused to fire again before I left for work. Fan keeps running. Pressure bar ok. Trickly watery noises at start up that seem new, but maybe I'm just straining my ears too hard. Also upstairs radiator, in bedroom, not bathroom, seems to get hot differently/more slowly than before last Vaillant visit. Other upstairs towel radiator in bathroom seems to heat as before - quickly and very hot.

Back to British Gas tomorrow, but not hopeful - every circuit board has now been replaced by either British Gas or Vaillant or both. Vaillant wash their hands, all but, but tell us that we don't need a new boiler - at least 8 years left. This Vaillant Thermo compact VC GB 282 E - installed circa 1995 has cost us nearly £300 so far - should we buy a new boiler? If so which one?

 

[oilman]

He says (and he is the first engineer to say this in 3 years of engineers) that it should be wired the other way round so that the power goes to the boiler then to the timer and back.

I know nothing about gas boilers, but if it has a test switch in, it is so the boiler can be switched on locall, regardless of controller inputs.

 

[DP]

Vaillants of that era were the BEST. Stop thinking of replacing it. Post question on Plumbingpages forum as well- Cam might have some advise.

Get the air pressure switch checked. The unit is located at the rear of the boiler. Check for 240 on both contacts with one meter lead connected to neutral

On this boiler the fan runs, air pressure switch detects differential air pressure to proceed with burner ignition.

I suspect your problem is lack of proper service. People you are with do not service- They provide maintance contract which is not a service. Service/ overhaul on this boiler can take upwards of 1.5 hours. Bet that has never been done. 15 minutes does not equate to a service.

 

[notsohandyandy]

We took heart from DP's reply - and went back to our service contract with British Gas - after a preliminary visit he said that 'we (BG) are clutching at straws' but will try replacing the air pressure switch. This coincided with DP's reply - which I mentioned to the BG guy when he called back with the switch last Monday.

We were very optimistic that it had been sorted - 9 days (with some hard frosts) and no probs. Until this morning! A little bit of snow outside and a very cold wind, and the heating cut out after about 30-45 mins. Switched it off - down to OC, switched it on, and it fires until the end of it's timer period. What on earth do we do now? Vaillant want to replace a circuit board, which we know BG replaced recently, and BG have no more ideas. How do we find someone we can trust to do a service - we have asked everyone we know to no avail. It has to be a new boiler, doesn't it?
Any advice so welcome - Sara (N5 - Islington)
P.S. How do I post this in the plumbing pages as DP suggests - they seem to have been integrated with heating?