External frost stat is in action or not doing anything?

[Jurgenjay]

Hi,

I have an external frost stat which I am not sure if it is in use or not. I had an electrician opened it and checked it, he said it is live. But he is not sure if it is in action or not....
I took a photo, could anyone confirm as the position it is, is this frost stat in action i.e. will protect boiler if temperature drops to some degree? If yes, what temperature it is set?

Thank you!

 

[John.g]

Measure or estimate the ambient temperature at the stat then just turn the dial slowly clockwise or anti clockwise until you hear a click, then note what reference mark, if any the temp setting on the dial that's closest to your measured temperature. (there seems to be a reference mark opposite 20C on the dial but very unlikely its set to this).
It should be set to 5C IMO.

Ensure boiler off before turning it up to check if boiler restarts, surprising the electrician didn't do this.

 

[Jurgenjay]

Measure or estimate the ambient temperature at the stat then just turn the dial slowly clockwise or anti clockwise until you hear a click, then note what reference mark, if any the temp setting on the dial that's closest to your measured temperature. (there seems to be a reference mark opposite 20C on the dial but very unlikely its set to this).
It should be set to 5C IMO.

Ensure boiler off before turning it up to check if boiler restarts, surprising the electrician didn't do this.

Thank you! Last night this Forum was down & could not open anymore....
Did you try to show me how to set the frost protection temperature? I am not sure about it.
Yes, I heard it should be set to 5C.
From the photo, are you able to see what temperature it is set to?

 

[John.g]

No, I can't really see from the photo where it's set to, its set to ~ 20C, if the REFERENCE MARK is where I am showing it with the arrow but as I said this is unlikely and why I suggest getting a household thermometer and measuring the (garage) ambient temperature close to the frost stat, then turn the dial clockwise/anticlockwise slowly until you hear a click, post a photo again when you hear/identify this.

 

[Jurgenjay]

No, I can't really see from the photo where it's set to, its set to ~ 20C, if the REFERENCE MARK is where I am showing it with the arrow but as I said this is unlikely and why I suggest getting a household thermometer and measuring the (garage) ambient temperature close to the frost stat, then turn the dial clockwise/anticlockwise slowly until you hear a click, post a photo again when you hear/identify this.

Hi John, Thank you again for your reply!

I just checked and turned the dial anti-clockwise, when I heard the click I stopped and took the photo(the green line & question mark is what you meant REFERENCE MARK, right?)---attached photo1;
The photo 2 is the garage temperature I just measured for where the boiler and frost stat locate;
The photo 3 is the original (without turning) position----At this position you cannot turn the dial clockwise anymore, it is to the end & stuck there----can only turn anti-clockwise.
As you can see from photo 1 and photo3, the REFERENCE MARK position is different now.

Also, when I heard the click---as per photo1 position, the boiler started to fire, burner light (green light) was on, and blue light was on, I went upstairs to see the zone valve for hot water opened & the pump made noise!

But I heard the external frost stat normally is wired to heating not hot water? Is my system correct?

Thanks!

 

[Gasmk1]

The arrow should be straight up the defence in the lager tooth sharp at top behind dial

 

[Jurgenjay]

The arrow should be straight up the defence in the lager tooth sharp at top behind dial

Thank you!
Did you mean the arrow (above"5") position should be straight up like attached photo? I marked a down-arrow on the wall, so is that the line should the arrow on the stat face up to?

 

[John.g]

The arrow should be straight up the defence in the lager tooth sharp at top behind dial

The 12 oclock position would seem normal all right.
The measured temperature is 12.5C and (photo1) so a setting of 8.5C which closed the contactsmeans that the stat has a offset (hysteresis) of 4C, if this is correct then the stat should be set at "2" or where it originally was which will close the contacts at approx 5C??.

 

[John.g]

Thank you!
Did you mean the arrow (above"5") position should be straight up like attached photo? I marked a down-arrow on the wall, so is that the line should the arrow on the stat face up to?

Yes, more or less correct, but a setting of 8.5C equals to your measured temperature of 12.5C so maybe repeat your test and if the same I would set the stat almost fully clockwise to its original setting of "2" which means that the stat will operate when the temperature is 5C?.

 

[Jurgenjay]

The 12 oclock position would seem normal all right.
The measured temperature is 12.5C and (photo1) so a setting of 8.5C which closed the contactsmeans that the stat has a offset (hysteresis) of 4C, if this is correct then the stat should be set at "2" or where it originally was which will close the contacts at approx 5C??.

The arrow straight up---if this means 5C then the original position(photo3) it means 0C?
My installer's boss who told me the installer(had left the boss) said"he had disconnected the external frost stat", if so, then the original position(0C?) means the frost stat is not in use?
Until today I turned the dial anti-clockwise and heard the click---which is photo1 position: the boiler started to fire, zone valve for hot water opened, green and blue light were on.
So at photo 1 position, the frost stat is in action? ---but today the garage is 12.5C which is too high for frost protection temperature?