Honeywell Three position valve


On my friends central heating I can't get HW on its own. It is basically a Y plan system. CH on its own is OK; the valve goes to position B, CH and HW OK valve in position A + B, but HW on its own the valve stays in the mid position. For HW only I should have both white and grey wires to valve inactive, but I am getting white staying live.
If I disconnect Orange at this point the valve moves correctly to pos A.
I am looking at this because of an original fault where the boiler case shorted through the supply wire insulation. This caused the HW contact on the programmer to stick in the ON position. Is it likely that the same fault damaged the contacts in the three pos valve?
Can I replace the actuator without draining the system?
TIA
Richard
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On Fri, 1 Apr 2005 08:42:50 +0100, "richard"

hi richard have you got a HW tank stat? the contacts on this may have welded stuck. yes you can get a new 'head' for the valve that way no draining nessasary regards bob
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Thanks for the info about replacement.
If the tank stat contacts had welded together, that wouldn't necessarily be the the reason I can't get HW on its own, would it?
In the HW only position the pump/boiler comes on but because the valve stays in mid position the CH runs as well.
Richard
wrote:

a Y

OK
fault
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Have you read http://www.diyfaq.org.uk/plumbing/plumbingpage2.html#midposition ?
I found it a most useful article. The valve I replaced required that the system be drained. The replacement does not.
--
Adagio



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