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

On Fri, 1 Apr 2005 08:42:50 +0100, "richard"
<richard@maninfodotcodotuk> wrote:


>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
>

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

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

"burbeck"  wrote in message
news:8a0q41lh11gn4n7ublmrd8796b06vf2v78@4ax.com...

> On Fri, 1 Apr 2005 08:42:50 +0100, "richard"
> <richard@maninfodotcodotuk> wrote:
>
> >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
> >
> 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

"richard" <richard@maninfodotcodotuk> wrote in message 
news:424cfb09_3@mk-nntp-2.news.uk.tiscali.com...

> 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
>
>


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