HW / CH problem


I have a gravity fed CH and HW system, approx 12 years old. We are now not using the CH part (summer??) but notice when the timer comes on to heat the water (twice a day) all the radiators get hot aswell just as though the CH was also selected. The system is run by a single timer unit with seperate programming for water and heating. The CH programme is definately set to off. Does anybody have a clue where I should start my investigations?
Cheers
John
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John wrote:

Look to see if the valve is stuck?
--
Sue


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Do you mean the valve in the airing cupboard with the silver box on top (three port valve??). If so how do I check if it is stuck can I manually open and close it?
Cheers
John
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John wrote:

It may have a little lever, on one side.
You may be able to hear it move (putting a long screwdriver against the case and the other end on the bone just uder your ear may help - by conducting the sound)
If you /very carefully/ remove the cover - bearing in mind that there is mains voltage in there - you may be able to see it move, or try to move.
If there is no apparent movement, no matter what - then you really need a test meter to see if its electrical input is changing. If that is, but the valve isn't moving, then it's stuck. If the electrical input isn't changing, then there is a wiring or controller problem.
It is fairly easy to replace a valve. The problems come with draining and refilling and with undoing nuts that may have seized in place.
Some makes and models allow the "silver box" to be replaced, leaving the "plumbing" untouched.
--
Sue










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In an earlier contribution to this discussion,

It may just have got 'confused'. You can reset it by removing *all* power from the system - by which I mean by turning the mains off at the FCU, not just at the programmer. When you do this, you may hear the valve move back to its rest (HW-only) position under the action of its spring return. It may then work ok when you switch back on again.
If that doesn't work, you need to investigate further by removing the actuator (the electrical part) from the 'wet' part of the valve. If, when removed, the actuator socket (the bit which fits over the spindle of the valve) immediately rotates to a diffeent position, it indicates that the valve is seized - or, at any rate, too stiff to be moved by the actuator's spring return. You should be able to rotate the spindle to and fro by gripping it with finger and thumb. If you can't, you may be able to free it by turning it to and fro with a pair of pliers. If that doesn't work, you'll need to replace the valve - which involves a partial drain-down of the system.
--
Cheers,
Roger
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On Wed, 25 Jul 2007 20:17:53 +0100, "Roger Mills"

Are you in IT?
Wires, switch contacts and relays in such a simple scheme do not in my experience ever get confused.
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In an earlier contribution to this discussion,

You may *think* that - in which case your 'experience' is rather limited! The actuator in a 3-port valve is actually quite complicated - with diodes etc., which cause the motor to stall in the mid position under appropriate circumstances. Mine has certainly got confused [1] on occasions, and has been perfectly ok again as soon as it has been reset by removing *all* power to it.
I have suggested the same solution in the past to a number of previous posters with a similar problem - and many have come back and said that it fixed the problem.
[1] where 'confused' is defined as a state in which the valve stays in one position and fails to respond to changes in demand even though the wet part of the valve isn't seized. This may well be due to a micro-switch failing to open or close at the right time, but is often fixed by doing a reset.
--
Cheers,
Roger
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