On 2008-07-12 17:10:08 +0100, "Stewart" said:

The MV2-22C Tower Valve on my central heating has failed and I shall have to
replace it.
I checked the price etc with a company called TFC and from them I see that
it is possible to replace the valve without draining the system however this
seems to be contradicted by their statemant that the replacement valve
includes compression fittings. I cannot see a need for compression fittings
unless the replacement valve (or motor etc) is subject to water pressure.
I opened mine up this afternoon and found that the problem appears to rest
with the spring that is pushed back against the micro switch; meantime I
have inserted a small packing piece and that has got it working but of
course that is temporary.
When I eased the pressure on the studs into the base plate then water
started to come out so I had to tighten them again.
Does anyone know if it is possible to replace this Tower Valve withoug
having to drain down the central heating system?
Thank you.

These kind of valves are fairly generic and while it is possible to buy
the motor heads and bases separately, it's often cheaper to buy the
whole thing.

If it is a motor and switching problem, you should be able to remove
the head only and leave the valve body in place. Doing that should
not cause a leak. I suspect that you have tried undoing the wrong
screws - the ones that hold the base body together. That will cause it
to leak. If you look carefully you should find that there are other
screws or fasteners that hold the head to the body and you need to undo
those.

Once the head is removed, check that you can turn the cam of the valve,
ideally with your fingers. It might need to be with pliers but the
cam should not be stiff. If it is, then it will be a case of drain
and replace the whole thing.

If you can just replace the head, it will be a matter of following the
wiring carefully with the new head.