My Vokera boiler is possessed by a Poltergeist - help !

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Weather's fairly warm outside, thermostat set to 20C, ambient temp 22C no need for CH to be on ....

I have a Vokera Linea 7, the timer on the boiler is set to "OFF", and yet every few hours (mostly at night) the boiler fires up by itself and all the rads get piping hot and the house really heats up.

I repeat - the Timer is set to "Continuously OFF."

I thought at first this was the "anti stick" function that I'm used to hearing go in the early hours of the morning, but that usually fires the boiler for a few seconds - not continuously for a few hours.

I was at home yesterday, and caught the boiler up to it's tricks during the day ... even though the boiler is set to Off.

I decided to switch off the system by turning the control knob to the middle OFF position, when I did this the boiler carried on running - the LED display goes out, the green light on the front goes out, except that the pump keeps running and the burners are going on full power.

The only thing I could do was to use the isolator switch to cut power to the boiler.

When I switched back on it behaved for 5-6 hours, then started running again even though Timer is Off.



Any ideas what needs replacing javascript:emoticon(':?:')

I have an engineer booked, but I just know they are not going to believe me, and I expect the boiler will not misbehave when the engineer gets here javascript:emoticon(':evil:')
 
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The divertor valve is probably stuck.
The hot water pre heat will be trying to heat the rads.
Or it could be a faulty thermistor acting in frost stat mode.
 
Thanks for the reply :)

I'd put my bet on a faulty Thermistor, or perhaps a relay sticking on all the time.

I eventually turned the boiler off completely for a few days because it was wasting gas running 24/7 ... I turned it back on 4 hours before the British Gas engineer visit (they were coming out to do the annual check anyway.)

British Gas engineer came, and of course the boiler is behaving properly now .... still charged £50 quid for not even checking for the cause of a potential fault though, although the fault is still covered if it occurs again in the next 28 days.

I'm playing a waiting game for the fault to occur again ...

Any ideas how I can reproduce the problem, as whatever it was has stopped now that the machine has been opened up ?
 
I'd put my bet on a faulty Thermistor, or perhaps a relay sticking on all the time

I'll have some of that bet if you like, what odds are you offering :LOL:

Seriously though, It will be a problem with the diverter and the preheat function.

You can disable the preheat by removing the jumper from j6(i think) on the pcb.
 
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Incidently if he has serviced it the the fault should have become apparent when running hw to test max burner pressure and when he telegan'd it.
 
Thanks for the reply :)

I'd put my bet on a faulty Thermistor, or perhaps a relay sticking on all the time.

If you know better than the boiler engineers on here who are advising you then one wonders why you bother to ask us.

To know exactly what is the problem you have to do some tests on the boiler. Without that luxury we can only guess at the most likely senario. Thats either a leaking diverter valve on DHW preheat or a high resistance thermistor ( which is easy to measure ).

A rather blocked plate heat exchanger will also cause the diverter valve to leak to the heating circuit.

Tony
 
Thanks guys !

You were spot on with the sticky valve diagnosis.

The intermittent fault happened again last night - ran the hot tap, luke warm water came out, however the rads were getting hot instead. It seems the pre-heat was also trying to heat up the whole system.

Many thanks for sharing the benefit of your experience.
 
I'd put my bet on a faulty Thermistor, or perhaps a relay sticking on all the time.

And you lost your bet too!

But then you would not play golf with Tiger Woods and expect to win against a professional!
 

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