Really appreciate your help on this. I shut down most of the rads and changed the PCB back to the old one. I checked the thermistor resistance last night and it was working. Works normally now. PCB was new so dont know why it was duff.
Its the 100e so only servers CH at 1 temp. I take your point about the expansion vessel.
I guess I maybe jumping the gun on the temperature. What would be a quick way to test it? Shut all the rads down and power on the boiler until it turns off, overheat gets triggered or pressure gets tripped?
Yes I've heard that, was one of the first things I tried to sort out the short cycling. Replaced the PCB and replaced the pump as there was poor flow in the far rads.
Ah ok. Makes sense. Just tried it out and don't think that's it. It was hot from before, ran for 10 minutes and didnt cut out. Return pipe scorching hot.
The boiler fires up at a minimum gas and then shoots to full gas for that long (20mins+). It was short cycling before (possibly related to the wax capsule head). The CH HW outlet and CH return are very hot after 20mins and the pressure goes up to around 2.5 bar. I'm concerned something may be...
I've just replaced the wax capsule head as it was leaking. Now the hot water works fine but the central heating wont turn off. Put it on constant and it just fires up for 20+minutes. Any idea what could be going on here?