Having got my oil fired rayburn back in good shape I turned my attention to why the radiators weren't getting hot yesterday.
During the summer I'd discovered a switch in the utility room which was live and on, but which I had no idea what it did. I disconnected it. It turns out that this switch was controlling the pump for the CH.
There is no CH/HW controller, as it's a pretty basic system, and no electronic control of the heat source (the rayburn). However, I'm confused with what I've got:
- A DP switch in the utility room, with the supply, the pump and, I think, the thermostat. - A pump on the CH feed. - A cylinder stat (like http://www.screwfix.com/prods/40051 ) strapped, not to the cylinder, but to the cylinder feed (which is branched off the CH return). - A SP switch in series with the thermostat. - I think the thermostat was wired in series with the pump, although I don't have notes of how everything was connected up when I disconnected it earlier in the year. (Lesson learnt.) - No diverter valve.
Now, I'm confused. This suggests that the CH pump should only operate when the feed to the HW is below whatever the set temperature is. Why would this be? It seems like this might be so that if the HW is cold then the hot water is fed around the CH and then to the HW, but I've got two problems with this: - the thermostat was set to 70 degrees and without the pump running the thermostat temp was above this, suggesting the pump isn't needed for the HW - why would I _not_ want the CH circulating in this kind of system (and if it isn't where's the heat going to go?).
Right now I've left the pump running 24x7. Are there likely to be any problems with this?