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Unable to switch heating off even with selector set to water

Postby jedkhan » Sat Jun 30, 2007 6:42 pm

I wonder if anyone out there can help sort the problem with my combi boiler, its an Alpha 240 Eco (Ocean).
The problem is I can't turn off the central heating, even with the selector switch set to hot water only and the clock switched off, the radiators still get hot. In the end I just switched off the power supply and only turned it on when I needed hot water, but now the pilot light has gone out and will not relight. Any clues please as to which part has gone wrong?
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Simply Build It

Postby plumbers1 » Sun Jul 08, 2007 8:49 am

Sounds like programmer problem.
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Postby mk-donald » Fri Jul 13, 2007 11:19 am

I had this symptom a good few years back with my regular boiler and programmer.

In the summer with the central heating turned completely off at the programmer I was still getting warm radiator, especially the 'first one' in the loop, ie bathroom radiator.

The BGas engineer diagnosed this as a faulty diversion switch in the airing cupboard - ie the motorised valve that sends the water heated by the boiler to either the hot-water tank and/or the radiator system. He replaced the motor in it. It happened again a couple of years later and they replaced the whole assembly.

eg screwfix parts 28670 and 53314

Not sure how/if this relates to a combi boiler system, but just raising it in case its helpful.
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Postby jedkhan » Sat Jul 14, 2007 9:06 am

Thanks Guys for your suggestions.

The combi boiler is directly linked to the hot taps ie no hot water cylinder and the only programmer is the clock with push in/pull out pegs to set central heating. This clock can be set to on, off or timed only. I did notice that the microswitch operated by the hot water does stick but even when it is released ie plunger is in it doesn,t make any difference, incidently when the hot tap is turned on the plunger does pop out and contact the microswitch and vice versa.

How would i disconnect the clock? I assume when it is in the off position it is off! Could someone tell what causes central heating to fire up if this clock is off as when i rang Alpha, the guy there simply said it was due to "differential pressure". I can,t seem to understand how there is a demand for central heating when everything is set to off.

Any help gratefully received.
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