S Plan Boiler ghost voltage?

[grahamBX]

I have a Potterton boiler which for 5 weeks has been not working with a series of error codes the latest being IE33. I have a contract for service but after most parts were replaced and 2 new PCBs it was still dead. So the manufacturer (Baxi) were called in and they found that there was a variable small voltage on the switched live (somewhere between 25- 50 volts). They declared that this was the problem and although they accepted that the PCB was likely to be the current issue they would not replace it again until the spurious voltage was removed as they believed it was damaging the pcb. The servicing agent are saying they cannot detect the spurious voltage so back to baxi i.e. a standoff.

One problem is that the engineers never speak to each other and just keep leaving notes for me to pass on when the next one arrives....

Has anyone see a problem like this where a low voltage (possibly ghost of course as read with digital multimeter) is capable of damaging the PCB? I would have guessed that a low voltage would be tolerated whereas I can understand that a higher voltage than expected may cause problems?

 

[Phoenix]

I would expect that the only effect that the 'ghost'/capacitivly coupled voltage would have would be to be interpretted as the signal to run, afterall the terminal is expecting 230v, and what its getting is the faintest sniff of 230v connected through a capitance in the nF range! A decent hardware design enginneer would mitigate this though. So unlikely to be the issue unless its spurious turn ons you are having, or you have the switched live wrapped around a lightning conductor

The stray voltages can be eliminated by connecting a switch suppressor between SWL and N

It is possible that the boards are subseptible to spikes and surges in which case some sort of suppression would be usful, its very common these days to bit type 2 surge suppression at the consumer unit in Domestic premises, and if the supply to the boiler is less than 10m then that would be all thats required, over 10m then often a local type 3 devcie is recommend locally to sensitive equipment

 

[grahamBX]

thanks for the info!

 

[SPECIAL LOCATION]

possibly ghost of course as read with digital multimeter.

These type of ghosts generally appear bigger than they really are if measured using a standard multimeter....

e.g. Its not uncommon to see anywhere between 40, to 70+volts floating on typical 2-way light switch strapper wires if using basic multimeter..

And switched live heating control wires are not that much different..

So this voltage could well be nothing at all..

:coffee