Thermostat not working?

[D_Hailsham]

1. If you turn the HW ON and the CH OFF at the old timer, do the radiators still get piping hot?

Why would the rads heat up with just the hot water on?

They should not heat up but, if they do, it's a sign that something is wrong, e.g the motorized valve is faulty or you have reverse flow (this is very unlikely as you would have noticed the problem before you changed the stat).

 

[gilford]

I have the hot water come on every morning and every night and I can assure you the radiators do not come on whatsoever.

So I suppose that is one good thing then?

 

[D_Hailsham]

I have the hot water come on every morning and every night and I can assure you the radiators do not come on whatsoever.

That means a motorized valve is not leaking.

Now carry out the second test to see if the boiler and thermostat work when CH only is on.

Incidentally how many motorized valves do you have? It will be either one 3-port or two 2-port.

 

[gilford]

Hi mate, sorry for the late reply, I have been away over the bank holiday weekend

I have just tried your test now, and even with the 907 set to 5 degrees and the TRV on full, the minute you push the heating on constant on the old honeywell timer it comes on

Turning the temp up or down on the 907 makes no difference whatsoever, the little "flame" clicks on at about 20 degrees (which is in the hall now I presume) and the unit makes a click noise as if to fire the boiler, but the boiler is already going full pelt in the boiler room outside