Heating not going off on timer

[cliffG]

Hi can someone offer some advice :
When putting the heating on timed it will not switch off, the hot water also on timed seems to be fine. The thermostat is an old ACL switchmaster SM805 the room stat is a switchmaster (no model number on the outside of the stat). I have tried putting the heating on constant and using the room stat to turn it down but that is not working. So does that prove it's the room stat at fault or could it be the timer. I am after some advice before i get someone in does anyone know a way to test what is at fault. I had this problem approx a month ago and fitted a new 3 port valve ( Drayton MA1 ) I went with a straight replacement but did buy a 2nd hand one off Ebay as currently out of work. This did fix the problem and was all fine until 2 days ago now problem as above. Any advice appreciated
Thanks
Cliff

 

[Daveydub]

So if you put it on water only does the heating still run?

 

[Daveydub]

It wont be clock or thermostat. It is just about possible that it is clock AND thermostat. Most likely is a bit of muck in 3 port valve so heating is off but port is not sealed. To test, turn on heating only, if not possible on your clock, put it on water only then turn cylinder stat right down so that pump & boiler have gone off. Now put heating on and room stat should now bring pump & boiler on. You can then prove that clock & stat are operating normally.

 

[cliffG]

Thanks for the replies i will try that today and get back to you.

 

[cliffG]

Daveydub, I have turned everything off at timer ; water off and heating off.the stat on the water cylinder i turned down to 0 so that should not come on and now turning the boiler back on ( that was the only way i could get the heating to go off in the evening ) the pump has started so does that mean the valve is stuck open ? I have waited a while and the rads are getting hot. This is before i could get to the part about turning the heating back on and using the room stat. If it is the valve is there a way to clear it without draining down Any advice would help.

 

[Daveydub]

the hot water also on timed seems to be fine

This does not now appear to be the case.
On the side of your 3 port valve you have an indicator to show water, mid or heating. When you switch water & heating on & off does this indicator move at all?
Turn electrics off. Remove timeclock from backplate (2 screw beneath need loosening). Turn electric on. Do boiler & pump now run?

 

[stem]

Do you have frost thermostat installed anywhere? These override the normal heating controls (thermostat and programmer) and put the heating 'on' to prevent the system freezing. Occasionally the frost thermostats go faulty or get inadvertently turned up so that the heating stays on permanently.

 

[cliffG]

I have now turned the water on constant at the timer and the indicator didnt move stayed in the mid pos M, putting the heating on constant same thing stayed on M. What does that mean. I have not done the timeclock bit as had to have power on to test the first part. Are you saying i need to turn heating / water to off on timer first then power off and lastly remove timer face and turn power on ?

 

[cliffG]

Stem I dont know if a frost thermostat is installed

 

[Daveydub]

Turn power off so that if you touch a terminal while removing clock you will be safe.
Now turn power back on. What happens?
Now replace t.clock so that there are no accidents.
At this stage we are just trying to establish for sure what the symptoms are not what the problem is.
It could be, valve gone faulty, valve wired incorrectly and you only just noticed the problem, frost stat that you have not noticed.
Do you have a multimeter and are you happy to use it?

 

[stem]

Stem I dont know if a frost thermostat is installed

To be fair, they are not overly common and are usually installed where there is a risk of exposed pipes freezing, such as outbuildings, basements, garages, occasionally lofts. You would probably know if you had one they usually look something like this.

 

[cliffG]

Davey,
Right could not get timer face off removed bottom screw and it had two lugs at the top that i could not get depressed but this is the first time i have switched it off at the spur. I usually just switch off the boiler. when i turned it back on at the spur and put water from off to constant the 3 port valve moved to W from middle. Turning this off it moved back to middle and then turning heating on constant it moved to H. with both on it's back in the middle. The valve was wired exactly as before when i replaced it a month or so ago.

 

[Daveydub]

To remove clock, loosen bottom screw (usually 2 but in your case it might be one), pull away from wall at bottom and unhook from top.Forget that for now as we should explore the symptoms further.
Here is what should happen:
W on, ch off. pump & boiler run, valve to W
W on, ch on, r/stat turned up, pump & boiler run, valve to mid
W. off, ch on, r/stat turned up, pump & boiler run, valve to h
W Off, ch on, r/stat turned DOWN, pump & boiler off
W Off, CH off, pump & boiler off
I am not clear how many of these functions are operating properly.
If all of them are,
at w.on, ch off position with valve to W, put your hands on the pipes around the valve. Is hot water flowing to the heating circuit despite the valve indicating that it is on water only

 

[cliffG]

Thanks Davey I have tested the above here are the answers
Switching power at spur off pump stops switch back on pump still stopped valve has moved to W

W on, ch off. pump & boiler run, valve to W yes correct but pipe to boiler hot
W on, ch on, r/stat turned up, pump & boiler run, valve to mid yes correct
W. off, ch on, r/stat turned up, pump & boiler run, valve to h both sides of valve stay hot valve stays on M
W Off, ch on, r/stat turned DOWN, pump & boiler off no, boiler and pump stayed on valve on M
W Off, CH off, pump & boiler off no stayed on valve on M


Cliff

 

[Daveydub]

yes correct but pipe to boiler hot

Did you mean that or did you mean pipe to heating?
Valve never moved to heating only position so perhaps hw off line from t.clock is not functioning.
To test this, hw & CH on & turn cyl stat down. Does valve now go to H & pump & boiler run. Does operating room stat now turn pump/boiler on/off