I'm not sure quite how you read that, but there you go!
Yes. One reason to have the bypass! Alternatively, you could use a couple of relays and run the pumps and relays from the valve switches to give an OR for the boiler interlock.
An ancient gravity circulated boiler is unlikely to have pump overrun.
Perhaps, although a twin pump solution would be an easier fix, as it leaves the CH circuit untouched.
Christian.
Boiler cycling, slugglish performace in re-heat, etc, etc.
That is so, then you fit another zone valve and cyl stat, so may as well have the lot fully pumped and increase efficiency.
Sorry, I've just re-read it - and I obviously read something into it which wasn't there!
But he would surely need to insert a zone valve into the CH circuit - or would he?
The thought has just occurred to me that with 2 pumps, and the boiler interlock logic implemented using relays, he may not need *any* zone valves - and almost certainly wouldn't need any by-passes. He'd just have to make sure that the HW circuit didn't continue to circulate by gravity when CH-only was demanding heat. This might require a null-flow valve on the cylinder side of the vent/feed connection.
Indeed. That's another method that can be used.
Christian.
I read the postings with interest, and gain a lot of knowledge on the way.....
I assume that the two pump option is similar in operation to the the grundfos pump plan which uses a dual output pump.
What puzzles me on this is if, say the HW circuit was being pumped by its own pump and CH was off, why there would be no circulation on the CH circuit without the a zone valve? i.e wouldnt the HW pump push water through the pump and around the CH circuit? (on the current gravity system, isnt the HW assisted to a degree by the pump when CH is on, as we are pushing pumped water into the boiler return)
There won't be a substantial pressure difference over the two ends of the unpumped circuit, so flow would be non-existent or very slight, easily stiffled by a flap type non-return valve (or the 2 port zone valve, of course!).
Christian.
After all this help I am temped to put in a second pump and go to a fully pumped system (second option for me would to go to C-Plan)
Benefit of second pump is that it leaves the CH circuit - as is, and should be cheaper than S-Plan as it only needs a pump (and I might be able to get my hands on one!!), which should be cheaper and easier than having to move the pump AND need to fit 2x 2ports AND a bypass.
The only thing that is puzzeling me is the "anti gravity valve" - what does one look like, and where can you buy one from. I have looked at screwfix, discountheating, BES etc and cannot fine what I need. - can anyone point me in the right direction. I would need a 28mm fitting.
thanks
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