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Central Heating Controls Not Working Properly

Postby gd1501 » Fri Jan 25, 2008 1:33 pm

The background and problems on my central heating system are as follows:

The boiler is wall mounted and located within an integral gagrage. It is fitted with a frost, which is set to 5 deg C. The internal thermostat is set to high for the winter period.

The roomstat is a digital wired thermostat sited on the 1st floor landing. It's temperature is set to 22 deg C.

The central heating and hot water are programmed to come on twice a day for around 4-5 hours each period.

The hot water cylinder has had a new honeywell cylinder stat fitted and new honeywell 3 way valve fitted around 7 months ago.

The problem was that when the heating and hot water were programmed to come on, only the hot water would stay on until either hot water was drawn form the system or the room stat was adjusted, then the rads would heat up.

I got the heating engineer out last weekend who fitted the various components last year and he checked them and said they were all operating as they should. He suspects the problem may lie with the wiring set-up of the frost stat and the boiler.

Since he visited, the problem has now changed so that now when the programmer is off, the roomstat temperature achieved, the boiler is still firing up and heating the rads!

I thought it might be a fault on the 3-way motorized valve fitted next to the cylinder, but the heating engineer says it is working fine.

It's very frustrating and puzzling :?: Does anyone have any thoughts as to what is causing these problems and more importantly how we solve them.

Any ideas would be greatly appreciated.


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Postby ericmark » Fri Jan 25, 2008 9:28 pm

My daughter had a problem and I went through all the wiring and could not see what could be the fault. In the end I stripped the motorized valve electrical head and found although the paperwork showed one switch there were in fact 3 micro switches one which was faulty.
The idea is the central heating thermostat moves the motorized valve which in turn switches on the boiler.
On the valve I worked on it had a leaver to set it to midway position in order to bleed the system moving this to bleed midway position got both hot water and central heating temporary running but both worked together.
The valve moved correctly just the internal switches did not switch. Try manual midway leaver and see if it runs then.

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