A quick update for anyone who's interested - fitted a valve on the H/W water circuit before the tee to the feed and expansion and all seems to be working just fine.
Thanks to all who offered advice - complicated stuff this central heating lark!
Thanks for your reply, the pump is before the tee.
I was worried about pumping over into the expansion tank when the h/w circuit is closed by the new valve and the central heating is circulating - am I worrying unduly then?
Re your point about an automatic bypass my system has TRVs on all...
I checked with heateam and it doesn't need an overrun as it has aluminium heat exchangers.
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I suppose I could fit a valve onto the cylinder return and see if all is OK. Apart from pumping over into or drawing in air from the feed and expansion tank should I worry about anything else doing this?
Two pipes connect to the boiler - I can't confirm 100% on the question of pump flow as the boiler is at one end of the kitchen (mounted high on the wall in the utlity room) and the pump and valves are at the other (behind a panel at the back of some base units in the kitchen proper) the pipes to...
I'm looking for advice on the best way to upgrade my central heating system. We live in a two story house with the boiler, pump and controls downstairs and the h/w cylinder upstairs.
The current system is open vented but without an independent hot water circuit (or cylinder stat for that...