Could anyone take a guess at what might be causing my Potterton Promax 24 HE to keep starting, running a bit, then stopping, then rinse-repeat ?
A little more for you on the setup - 3 channel central heating (2 heating circuits, 1 hot water), 2 thermostats for the heating, an upstairs one and downstairs. Both Potterton PRT2's.
When both thermostats are calling (and hot water circuit is off), the system fires fine and keeps running. But when the downstairs thermostat stops calling the above cycle starts.
I've tried swapping the thermostats front plates around to check it's not the thermostats themselves, but always happens when upstairs is off, and downstairs is on, regardless of the frontplate on the thermo. So figuring it's not the thermostats themselves.