Ravenheat completely cutting out CH, tapping PCB housing works

[jaymi]

Hi,

I have a Ravenheat LS100 Silverstar.

When the CH is on, it has started cutting out. When I say cutting out I mean everything immediately stops. The pump stops the fan stops, as if the power has been cut, but there is still power to the unit.

Tapping the side of the control board housing causes it to spring into life. I have wiggled all the wires, to no effect. The only two things that will get it to come back on are to wait 20 minutes or to tap the PCB.

Depending on the setting, tapping the PCB will do one of two things: if after it cuts out you manually turn the timer to off and immediately tap the PCB this will simply cause the pump to run for a couple of minutes before the usual timed shutdown, if you leave the timer set to on, then tapping the PCB will cause the whole lot to fire back up.

I am thinking of starting with replacing the PCB, is this a good idea?

Thanks,
Jamie

 

[rochdalegas]

Getting someone in who knows what they are doing would be a better idea.

 

[jaymi]

Thanks am trying to do a bit of initial investigation first but that may well be the end result.

 

[rochdalegas]

It can be expensive lesson to just start throwing parts at it especially expensive pcbs. For whats its worth the thermistors are a quite prone to playing up and are lot cheaper to change sounds lile a overheating issue to me. Again it would be better to carry out some basic checks first before changing anything.

 

[jaymi]

Thanks for the reply. I thought about the thermistors, but whenever that kind of issue has come up the pump would always keep running until the x minute time out even though the boiler would shutdown. With this problem however, when this cuts out everything stop immediately, including the pump, unless you tap the pcb housing.

 

[jaymi]

So a quick recap:

The boiler will start, radiators heat up, hot water will be delivered via a tap but after about 15 minutes it will cut out, not a normal cut out, the flame, fan and pump all stop at once as if the power had been cut. No hot water or CH is then available until at some later indeterminate point.

So I think I have ruled out the thermistor, to do this I disconnected the thermistor when the boiler was running and this causes the flame to go out but the pump keeps running. That is different to the issue I have, which is, both the flame, the fan and the pump all stop at once, as if the power has been cut. I don't think it is the a boiler lockout as the time to when it will switch back on varies wildly from 5 minutes to 2 hours.

I checked the voltage to the pump, when you turn the boiler on and it works, 240volts go to the pump but when it does not work there is no voltage to the pump, but here is what is a bit strange. If you tap the pump, this causes some kind of switch on the main pcb to 'fire' and the boiler does then sometimes start. But this does not seem to be a pump issue because as I tried supplying 240 vaults to the pump manually and the pump ran normally. I think the tapping of the pump is maybe more a vibration issue that is causing the system to start.

Right now the boiler will run for about 15 minutes max.

I am not sure what else to check, it seems the voltage to the pump should happen pretty early in the process so if that is not happening is there anything else to check? Would it help if I uploaded a video of pump tapping!?

Thanks for the help.
Jamie