Have I got a problem with froststat

[Parcival]

A few weeks ago we woke to find the heating on (gas with Vaillant EcoTec boiler in garage). The weather was very mild.

Plumber came and said it was likely the 3 port valve in the airing cupboard. Changed it but made no difference. Also changed the drayton timer unit - also made no difference.

Went to garage and took cover off the Honeywell froststat. Said it was all bashed up inside (not sure how and I did not see it - frosstat is over 20 years old). Anyway he put all the wiring back together and said it would be fine. Anyway 3 weeks on we woke up to the heating on again.

Happy to replace froststat if confident it will solve problem.

Thought much appreciated.

 

[JohnD]

have you got a wireless room stat?

 

[Harry Bloomfield]

A few weeks ago we woke to find the heating on (gas with Vaillant EcoTec boiler in garage).

Doesn't that boiler include built-in frost protection? My Vaillant does, so pointless to add a frost stat in the same area as the boiler.

 

[ianmcd]

Doesn't that boiler include built-in frost protection? My Vaillant does, so pointless to add a frost stat in the same area as the boiler.

If a boiler is in an outhouse or garage , it is best practice to fit a frost stat and pipe stat to protect the pipes in that area, an on board frost stat only protects the boiler nothing else

 

[Harry Bloomfield]

If a boiler is in an outhouse or garage , it is best practice to fit a frost stat and pipe stat to protect the pipes in that area, an on board frost stat only protects the boiler nothing else

OK, but the boiler, because of the flue, would generally be the coldest part of the wet installation.

 

[ianmcd]

OK, but the boiler, because of the flue, would generally be the coldest part of the wet installation.

But the boiler internal frost stat wont protect pipe work, a combination frost stat and pipe stat will

 

[Parcival]

Thanks for replies. Yes, as I understand it the boiler does have built in protection. The froststat was left from a previous boiler that didn't.

No wireless thermostat just an old fashioned one in the hallway and TRV's on all of the rads bar one.

Heating comes on regardless of time clock and regardless of hall thermostat. The only way to stop boiler firing the central heating is via the temp dial on the boiler itself.

Hoping new Froststat will cure the problem....

 

[stem]

If this is a regularly occurring fault, it should be fairly easy to test. Disconnect the froststat for a few days (whilst the weather is mild and no risk of freezing). If the problem disappears then it's the froststat, if it doesn't it's something else.

 

[Parcival]

It seems that all the electrics go though the Froststat. It would seem that disconecting it would cause the boiler to fire continually....

 

[oldbuffer]

It should be wired with:
1. A froststat to turn the boiler on when the temperature drops below a set level (5 degrees or thereabouts).
2. A pipestat to turn the boiler off again when the pipe to which it is attached (return) reaches a higher set level (10 degrees or thereabouts).
That way, the froststat turns the boiler on when it gets too cold, but the pipestat stops it running all the time. Note that the froststat tests the air temperature.

 

[Parcival]

Agree with all that but question remains - is a broken Froststat likely to be the cause of the original problem.

 

[denso13]

It seems that all the electrics go though the Froststat. It would seem that disconecting it would cause the boiler to fire continually....

This should be simple to test, there are normally only two wires connected and disconnecting one would take the frost stat out of the system.

 

[Harry Bloomfield]

Agree with all that but question remains - is a broken Froststat likely to be the cause of the original problem.

The frost stat should be wired so as to bypass everything else and switch the boiler on. If you disconnect it, then that should fix the issue, assuming it is the cause of the issue.

Normally, you can be almost certain an old style bi-metal stat is working properly, if you turn the adjuster end to end - if it clicks going both ways and at approximately the correct ambient temperature, then it is working.