It will if the last demand was for CH.Alarm bells started ringing when I read this:
if I set hot water only valve travels across
The valve doesn't move for HW only as the HW port is open when the valve is not powered.
Cold feed should be between open vent and pump and less than 6 inches from the vent
Shame the boiler doesn't have an overheat stat or you could just combine them.
Agree with stormer!
Overheat stat is a manual reset if the boiler reaches a set limit (usually 90 degrees or so) to stop boiling. Combining cold feed into the open vent is literally as it sounds... Just T'eed in! But shouldn't do it without an overheat stat on the boiler.
and feed pipe is plumbed to cylinder return.
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