Potterton Performa 24, CH ignition goes on and off in a loop

[Clint000]

Hi Tony,
thanks for jumping into this issue!

I have checked the DHW microswitch as well.
It seemed to work ok, I tested between the NC and COM pins and there was good contact resistance. The actuation of the NO and COM pins is also ok, and demonstrated by the correct functioning of the DHW.
What I was trying to discard was the NC pin playing up when the heating was on, but that is confirmed to work OK.

 

[bengasman]

Which ones can trigger a re-attempt to ignite?

Sensor, wires, connectors and board

 

[joshjames]

good point as bengasman mentioned any dirty conenctors or not clean contact or wires pinched etc could cause an intermittent fault

did you test the sensor hot?

 

[Clint000]

Just measured the sensor when hot and the reading is around 5.5kohm.
The overheat thermostat is showing good contact, which is strange as manual says it should read >1,5ohm...??

But then if the overheat thermostat was faulty, the DHW would not work either, would it? Unless this thermostat is only enabled when in CH....

Any ideas?

Also thought about the air pressure switch. It is the only one I have not checked, could that cause the issue?

 

[joshjames]

overheat stat you want low resistance - could be a board fault then

 

[Clint000]

Any other checks I can do before going the expensive route of replacing the PCB?


Thanks

 

[joshjames]

not sure why the pcb would be doing this - is there any burn marks or scorches on the pcb anywhere? or any wires/connectors that are not clean/sound in place?

 

[Clint000]

PCB actually looks very clean. There is one resistor, R73 which looks a bit more brownish than normal, but have measured its resistance and is as per the color code, so I see no reason to suspect.

 

[joshjames]

have you called the techline and asked them for any known issues on this?

 

[Clint000]

No, do Potterton have phone technical support for boiler issues?
I did not think about that route since whenever I call for any other support is never effective, but if you have had a better experience with them I could try.

 

[joshjames]

is the thermistor pocket packed with thermal grease?

 

[Clint000]

yep, there is some thermal grease in there, not enough to squirt out of the thermistor when you put it in, but there is some.

 

[picasso]

I would have the min/max gas pressures checked, my money would be on either the gas valve solenoids or board.

 

[Clint000]

Hi picasso, thanks for joining in.
Gas pressure has not been checked. However, if the gas pressure was not correct, would that affect the DHW as well as the CH?

I had an engineer in to fit a new 22mm gas pipe about 3 weeks ago, since the last 3-4m of the gas installation were made in 15mm. Could it be that after the installation he did not adjust the pressures in the boiler to the new pipe size?

 

[gas112]

As the hot water works ok that would indicate the min/ max setting on valve are ok as it would show up on HW going hot and cold.

Also as HW is working ok this indicates the actual working of the boiler is ok so its a case of looking at what controls the heating.
Very very ocassionally it might be the board .
But i would still be looking at the sensor.

Bengasman Know what your thinking re swapping the sensors over but thes only have them on the heating unlike the 28`s and 105`s