We have a CH system which has a Potterton "Netaheat" boiler running on bottled gas (big tank in the garden). It's a fully pumped system with a Honeywell ST7100 controller.
It only gets turned on occasionally, when we have visitors and, as now, when it's particularly cold.
However, this time, it's not starting up properly. The boiler fires up UK, gas lights etc. but after a while (I presume) the water overheats and the 'overheat thermostat' trips and turns everything off.
I *think* the problem may be that the pump isn't running, so, as it's a pumped system, it's not surprising that the above sequence occurs.
I did move some of it's wiring (the external wiring away from the boiler by the ST7100 controller) a while ago and I'm wondering if I may have mis-wired something. I did check quite carefully when I disconnected and reconnected but I *might* have got something wrong. I have wiring diagrams for the ST7100 and the boiler so I can ultimately check from first principles.
However I'd like a sanity check on how things are supposed to work. Am I right in thinking that the pump is powered via what the boiler wiring diagram calls the "Hot Water Thermostat" such that the pump will only run when the water has reached a certain temperature and will continue to run until it has cooled down. That's how it would appear to be (from the diagram) but that's depending on some assumptions about how a "Switch" works etc.