[Avulon]

Originally Posted by macafee2

What you say makes sense but this tank is 490/495 litres. This seems awfully large. There are only 5 radiators and one of those is turned off but there is also underfloor heating that we have not used. Still 490/5L is still very big. All 3 pipes have motorized valves fitted and I would have thought only the flow in or flow out would need a valve to control flow through the coil. Why would the vent need one? The vent connects to the central heating I think. There is an expansion vessel connected to the central heating return but that is in another room. I would need to double check but in the loft either the flow or return to the log burner has a pipe that goes to a header tank, would this not double as expansion. I am sure the other pipe has a pipe connected but I cant think where it goes. This flow and return for the log burner go through a coil in the loft cylinder, the heated water goes to the central heating. There are 2 thermostats connected to the central heating flow at the top of this water cylinder. The first is set to about 30 degrees, when at 30 degrees it opens a valve or two or 3 goodness knows and may or may not start a pump and heated water is then sent to the central heating. The second thermostat is set to about 80 degrees, when this gets to temperature heated water is sent to the 490/495 water cylinder and opens a motorized valve to allow flow into the 490/5 cylinder, I don't know about pumps or any other motorised valves opening.

Avulon, does any of the above make sense? You have had a very good thought, thank you for piping up, any more thoughts?

macafee2

IANAE - Consult an expert- for safety's sake.