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Central Heating comes on with HW only

Postby lucyc » Fri Jan 18, 2008 1:36 pm

When I put my hot water on the central heating comes on also, even if it is off on the timer. It never used to do that. Also, sometimes it will turn off even though the hot water is still on. We do not have a combi boiler.

Any ideas?
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Postby htg engineer » Fri Jan 18, 2008 2:41 pm

Sounds like the actuator is sticking, this is a motorised head that sits on top of a 3 port valve. When CH or HW or both is selected the actuator head turns the valve to that position - which diverts the water where required.

Knowing abit about electrics would help.

As I don't know the layout of your home it is quite diffcult to advise where this would be found - they are normally in the airing cupboard, behind a false panel in the chimney breast or in the loft. If you know where the pump is - it's a good place to start checking.
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Postby AlisterG » Fri Jan 25, 2008 10:37 am

Just discovered a similar problem in my CH/HW. Looks like a combination of a sticking actuator mechanism and water finding its way round the port valve itself. Initially I only got CH, with the actuator stuck in that position, electrical testing reported correct signals but the actuator failed to move, apparently caused by a sticking mechanism that corrected when I stripped the actuator down and reassembled.

Then the CH heats up when the HW is on and vice versa, despite the indicator on the side of the actuator reporting one being shut. Anyone had similar problems with Drayton MA1 3 ports?

Should I expect to see a load of toot fouling the valve after draining down the system? The system is 18 months old in a house of the same age.
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