Thermostat not working?

[gilford]

We had our hall decorated in April and I replaced our old thermostat with a Honeywell CM907, mainly because it looks good

What with all this rain and it being 9 degrees here tonight I thought I would be the heating on for an hour seems as though it hasn't been on for over 4 months.

I noticed that the thermo is doing sod all It say the hall is 20 degrees and there is no flame logo ie the boiler should not be working, but all the rads are piping hot????

Now I'm no master at this but I'm guessing that the boiler should only fire up when the thermo clicks on?

I have reduced and increased the temp manually and it does make a clicking noise and the flame logo does come on, but from what I can see it is not doing what it should with the boiler, otherwise the heating would not be on now surely??

Cheers

 

[spacethegas]

wired incorrectly ?

 

[seco services]

what heating system have you ?

if a mid position valve is letting by when hw on then the rads will get hot.

 

[gilford]

wired incorrectly ?

It is wired exactly as the instructions state?

 

[gilford]

what heating system have you ?

if a mid position valve is letting by when hw on then the rads will get hot.

I have a very old oil boiler, but it was serviced in Feb this year and the guy said it was running well at 82% effeciency

The hot water was not on @ the time?

 

[D_Hailsham]

What type of timer or programmer did you have before you put in the CM907?

How did you change the wiring to the old timer/programmer so it no longer controls the CH times, only the HW times?

 

[gilford]

What type of timer or programmer did you have before you put in the CM907?

How did you change the wiring to the old timer/programmer so it no longer controls the CH times, only the HW times?

No mate, I have replaced the thermostat, I have a timer in the dining room.

It has directly replaced an old dial thermostat on the wall in the hall

 

[D_Hailsham]

No mate, I have replaced the thermostat, I have a timer in the dining room.

It has directly replaced an old dial thermostat on the wall in the hall

But the CM907 is a combined timer and thermostat. Did the timer in the dining room previously control both CH and HW times? If so, how have you disabled the CH timer on the old timer so the CH times are now controlled by the CM907?

 

[gilford]

I haven't, I use the Honeywell in the dining room for timers, and the C902 in the hall purely for a digital thermostat that looks good

My plan was to use it as it was intended come winter and just leave the heating on constant in the dining room, when I get this damn to work!

 

[D_Hailsham]

wired incorrectly ?

It is wired exactly as the instructions state?

So which of the many wiring diagrams in the instructions did you follow?

From what you say, you have managed somehow to bypass the CM907, so the thermostat is having no effect and the boiler is on all the time the CH is on at the old timer.

Check your wiring and if you are unsure of what it should be post a diagram of what you have.

 

[gilford]

Sorry to be a pain with this, if you look at this thread -

http://www.avforums.com/forums/showthread.php?t=702458&highlight=thermostat&page=2

it gives you the info I was given to wire the thing. Probably wrong?

Cheers

 

[D_Hailsham]

Sorry to be a pain with this, if you look at this thread - ... it gives you the info I was given to wire the thing. Probably wrong?

Had a look at that thread and the wiring instructions appear OK. Presumably you have used just the red and yellow wires and disabled the blue and earth.

You need to check where the other end of the red and yellow wires terminate.

The red should be connected (via the terminal block) only to the CH ON terminal of the old timer.
The yellow should be connected (via the terminal block) to the boiler.
If you then leave the CH on the old timer set to continuous or 24hr (i.e permanently on) the CH times will be controlled by the CM907.

 

[gilford]

Had a look at that thread and the wiring instructions appear OK. Presumably you have used just the red and yellow wires and disabled the blue and earth.

You need to check where the other end of the red and yellow wires terminate.

The red should be connected (via the terminal block) only to the CH ON terminal of the old timer.
The yellow should be connected (via the terminal block) to the boiler.
If you then leave the CH on the old timer set to continuous or 24hr (i.e permanently on) the CH times will be controlled by the CM907.

This is exactly what I have done, but it still fails to switch the boiler when the target temperature is achieved?

Does it matter that I have the TRV's set differently?

 

[D_Hailsham]

Does it matter that I have the TRV's set differently?

Wot TRVs First time you have said anything about TRVs

Are you saying that you have a TRV on the radiator in the hall which is set to say 3 while the CM907 is set to 21 or 22? If so the wall stat will never shut the boiler off as the TRV has shut the radiator down at a lower temperature. So the hall will never reach the temperature set on the CM907.

You should not have a TRV on the rad near the wall stat.

You can either set the TRV to Max (assuming this is a higher temp than the wall stat setting) or change the valve to a standard wheel head valve.

Going back to your original post:

I noticed that the thermo is doing s** all. It say the hall is 20 degrees and there is no flame logo ie the boiler should not be working, but all the rads are piping hot????

Now I'm no master at this but I'm guessing that the boiler should only fire up when the thermo clicks on?

I have reduced and increased the temp manually and it does make a clicking noise and the flame logo does come on, but from what I can see it is not doing what it should with the boiler, otherwise the heating would not be on now surely??

1. If you turn the HW ON and the CH OFF at the old timer, do the radiators still get piping hot?
2. If you turn the HW OFF and the CH ON, does the boiler light when you turn the CM907 stat up to max and go off when you turn it down to min?

 

[gilford]

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?

2. If you turn the HW OFF and the CH ON, does the boiler light when you turn the CM907 stat up to max and go off when you turn it down to min?

I'll try this tonight and let you know.

Thanks for this mate, you are being a massive help