Honeywell CM907 constant flame shown

[Nagartath]

HI, I have a Honeywell CM907 which apears to be behaving strangely. THe room temp will be reached but the thermostat still has the small flame showing (indicating a signal to the boiler to fire up?)

As I am sad I waited for ages and the boiler eventually turned off but I think this was becuase it had reached temperature and not due to the thermostat as this still showed the flame.

If I play with the target temp I can get it to turn off by lowering it.

Any suggestions as to what the problem may be.

Thanks anyone for your help
Duncan

 

[Whitespirit66]

How long does the stat keep the flame sign and boiler on after set temp is reached? Has it always done this?

Is it a new stat by any chance?

 

[Nagartath]

In the past the stat would reach temp, "flame" on stat would go out then about 2 mins later the boiler would shut down (pump I think is about 5 mins).

It has only started doing it since we had the actuator changed but I cant see how changing this part would impact the op of the stat.

The stat has been in place since end of 2012.

I replaced the batteries thinking that might be the problem but unfortunately made no difference.

Hope that helps

 

[Whitespirit66]

Thought it may have been the TPI way that these stats operate that sometimes keeps them on a short while after set temp is reached. The TPI doesn't run strictly to set temps, but also fires boilers based on the length of time it thinks will be needed to heat the property. They can be a little confusing.

However, if yours is staying on way past set temps and you have to adjust the set temp down to switch off, there may be a fault with the stat.

 

[Nagartath]

What does TPI mean? Sorry I'm not a heating engineer.

I have heard there are some "installer settings" where I can adjust the temp by +/- 0.5C (inc of 0.1C)

Would these come into play at all?

i.e temp set to 21C stat does its weird thing I lower it to 20.5C would it still be in the threshold? (That makes as much sense as my signature!!)

 

[Whitespirit66]

TPI is explained on here.

http://www.homexpertbyhoneywell.com/en-GB/HintsTips/FAQs/Pages/faqs.aspx

I would only look at installer settings if something had been altered.

 

[Bilabong007]

Hi,

I have the 927 version and it seems the flame icon doesn't mean the boiler is firing. I think it means the room temp is in the range where the stat is thinking about firing up the boiler.

Mine has always behaved this way, maybe you just noticed it as you had work done.

Graeme

 

[Nagartath]

@Bilabong007 OK that sounds good to me. Like you say I probably only noticed it as something was changed.

Thanks to you both for taking the time to look at and respnd to my post.

Duncan