Frost Stat Query

[Rautospoon]

I had a Vaillant ecoTech Plus Open Vent boiler fitted in my loft about 6 months together with replacement Honeywell Frost (set at 5C) and Pipe (set at 25C) stats - these temperatures follow the makers instructions.
These replaced 30 year old boiler and frost and pipe stats, again in the loft to my bungalow.
I am aware that the boiler also has "built in" frost protection.
I am a bit obsessed with / paranoid about burst pipes caaused by frost, as my neighbours bungalow was severely damaged a couple of years ago caused by a leak in his loft, albeit his boiler is in his garage.
The new boiler has been fantastic, but before I contact the installer on this matter, a couple of queries to "get some information".
1. The boiler has "come on" a couple of times when "set to off" on Drayton Programmer and the ambient temperature was above 5C, then goes off after about 5 seconds.
2. When I turn the frost stat dial to above the current ambient temp (and it "clicks") to "say" 15C the boiler does not "turn on" - presumably it should as the external frost stat is meant to override everything ? (Basically the frost stat should turn the heating on when the ambient temperature falls below whatever temperature the frost stat is set at ?)
Any info and ideas would be appreciated. Many thanks.

 

[gas112]

is your boiler coming on after using a cold tap it could be a little bit of a dead leg it may even just be the built in function of briefly turning the pump on momentarily every 24 hours .
turning your frost stat up wont bring the boiler on if the pipe stat is satisfied . thats what its there for so boiler doesnt run constantly in cold weather

 

[dilalio]

I had a Vaillant ecoTech Plus Open Vent boiler fitted in my loft about 6 months together with replacement Honeywell Frost (set at 5C) and Pipe (set at 25C) stats - these temperatures follow the makers instructions.
These replaced 30 year old boiler and frost and pipe stats, again in the loft to my bungalow.
I am aware that the boiler also has "built in" frost protection.
I am a bit obsessed with / paranoid about burst pipes caaused by frost, as my neighbours bungalow was severely damaged a couple of years ago caused by a leak in his loft, albeit his boiler is in his garage.
The new boiler has been fantastic, but before I contact the installer on this matter, a couple of queries to "get some information".
1. The boiler has "come on" a couple of times when "set to off" on Drayton Programmer and the ambient temperature was above 5C, then goes off after about 5 seconds.
2. When I turn the frost stat dial to above the current ambient temp (and it "clicks") to "say" 15C the boiler does not "turn on" - presumably it should as the external frost stat is meant to override everything ? (Basically the frost stat should turn the heating on when the ambient temperature falls below whatever temperature the frost stat is set at ?)
Any info and ideas would be appreciated. Many thanks.

IIRC vaillant internal protection brings pump on (not flame) at <12°C

 

[Rautospoon]

IIRC vaillant internal protection brings pump on (not flameT) at <12°C

Thanks for that, but why does it "go off" so quickly after only a few seconds ?

 

[Rautospoon]

is your boiler coming on after using a cold tap it could be a little bit of a dead leg it may even just be the built in function of briefly turning the pump on momentarily every 24 hours .
turning your frost stat up wont bring the boiler on if the pipe stat is satisfied . thats what its there for so boiler doesnt run constantly in cold weather

Many thanks for that. Don't think I had used a cold tap before but what is a "dead leg" in this context ?

You mention "the built in function of briefly turning the pump on momentarily every 24 hours" - is that a well known function as I have never heard about it previously ?

 

[gas112]

Many thanks for that. Don't think I had used a cold tap before but what is a "dead leg" in this context ?

You mention "the built in function of briefly turning the pump on momentarily every 24 hours" - is that a well known function as I have never heard about it previously ?

yep a very well known function ben in certain boilers for past couple of decades .
Dead leg ignore my comment i missed it was an open vent boiler and not a combi

 

[dilalio]

Thanks for that, but why does it "go off" so quickly after only a few seconds ?

Speak to vaillant for full details but I think it's just to move water around the system. It'll be documented somewhere.

 

[dilalio]

Does say minutes not seconds!
So, maybe you have another issue.
Call them up and maybe get them round.

 

[gas112]

only 5 seconds does sound a bit strange and would rule out faulty microswitch on motorised valve bringing it on as it would stay on constantly .

 

[Rautospoon]

I seem to have received 2 totally differing replies, one relating to the "built in" boiler frost protection (lasting minutes) and one relating to a
"built in function of briefly turning the pump on momentarily every 24 hours".
As my boiler is almost new, am I right in thinking that the latter explanation is likely to be the correct one ?

Just out of interest is the temperature of the water in the boiler likely to fall fall below 12°C under normal domestic operating conditions between Spring and Autumn ?

 

[Rautospoon]

only 5 seconds does sound a bit strange and would rule out faulty microswitch on motorised valve bringing it on as it would stay on constantly .

A new pump and 3 way valve was also fitted 6 months ago.

 

[Rautospoon]

I have just sent an email to Vaillant Technical on this matter and will advise of response.
Many thanks for all responses to date.

 

[gas112]

Just a thought is it at same time every day or does it vary

 

[Rautospoon]

Just a thought is it at same time every day or does it vary

I have only actually noticed it a couple of times (and presumably have missed others) but cannot remember the times.

 

[dilalio]

Just a thought is it at same time every day or does it vary

You thinking a nulled time on the programmer for an unused Heating period? ie: on at 12:00 off at 12:01?