A pipe stat is needed?

[Jurgenjay]

Hi,

I have a newly installed boiler which has built-in frost protection, when the installer installed this boiler, they did not disconnect the old external frost stat which is still wired to the boiler.
I assume no newly installed boiler is still wired with old external frost stat, right? So I intend to disconnect the external frost stat (it might has caused my boiler in garage to fire in a cold day and lasted nearly 4 hours!)

When the external frost stat is in use, I heard "Now the frost stat should be wired in series with a clamp on low temperature pipe stat on the return to the boiler, which SHOULD open the CH zone valve to dump the heat. The return clamp on stat is usually set to about 20°c and when the return water reaches that temperature the stat contacts will open and cut power to the CH valve and in turn the boiler. Without this additional clamp on stat you will get constant cycling at the burner.Remember the idea of this setup is to prevent the boiler from freezing, while using as little fuel as possible."

I understand the above mentioned pipe stat is for external frost stat with boiler in the garage.

But if I disconnect the external frost stat, do I still need to install a pipe stat on the loft pipe?
Or the pipe stat can function itself which does not matter with or without external frost stat?

@John.g @SJB060685

 

[EvilDrPorkChop]

Firstly is this a heat only, system or combi boiler?

If you disconnect the frost stat, the only thing the boiler will do is circulate the water around the bypass whether that be internal or external. So the only thing the internal frost stat is doing is protecting the boiler and not the full system.

The current frost stat would protect the full system, as it would open the CH valve and heat the radiators, but yes should really be installed with a pipe stat to prevent it running for long periods of time. Should it fire, it will only fire for so long before cutting the power once the return temp is hot enough.

 

[Jurgenjay]

Firstly is this a heat only, system or combi boiler?

If you disconnect the frost stat, the only thing the boiler will do is circulate the water around the bypass whether that be internal or external. So the only thing the internal frost stat is doing is protecting the boiler and not the full system.

The current frost stat would protect the full system, as it would open the CH valve and heat the radiators, but yes should really be installed with a pipe stat to prevent it running for long periods of time. Should it fire, it will only fire for so long before cutting the power once the return temp is hot enough.

Thank you for your prompt reply!
It is heat only boiler with unvented cylinder system.
For my Worcester Bosch Greenstar boiler, the manual regarding the built in frost protection says "If the temperature within the boiler falls below 8°C the pump will run to circulate water and prevent the system freezing. If the temperature within the boiler falls below 5°C the boiler will fire periodically, bringing the boiler temperature up to 12°C to avoid the possibility of the system freezing. This process will be repeated until such time that the boiler temperature does not drop below 5°C."

You are right for internal built in frost protection the boiler will circulate first, if even colder weather it will fire periodically.---This looks only protect the boiler but not the full system.

So you reckon I keep the old external frost stat so that it will open the CH valve and heat the radiators---the whole system?
By the way, in recent years with the old boiler replaced & new boiler installed, gas engineers keep the old external frost stat or install a new external frost stat to work together with built-in frost protection?

 

[EvilDrPorkChop]

Depending on the circumstances, i'd of installed a new Frost Stat and Pipe Stat.

Depends where the boiler is and how the pipes are in the house. For instance if the boiler was in the garage that's uninsulated, along with suspended floors in the house with piping underneath i'd install a external Frost Stat.

If the boiler is internal to the house, and it's well insulated with pipes internal then i'd just use the boiler Frost protection.

 

[SJB060685]

Depending on the circumstances, i'd of installed a new Frost Stat and Pipe Stat.

Depends where the boiler is and how the pipes are in the house. For instance if the boiler was in the garage that's uninsulated, along with suspended floors in the house with piping underneath i'd install a external Frost Stat.

If the boiler is internal to the house, and it's well insulated with pipes internal then i'd just use the boiler Frost protection.

I believe this website user is someone from another thread a few weeks myself and others were collaborating with. If so the boiler is mounted in a garage.

 

[Jurgenjay]

Depending on the circumstances, i'd of installed a new Frost Stat and Pipe Stat.

Depends where the boiler is and how the pipes are in the house. For instance if the boiler was in the garage that's uninsulated, along with suspended floors in the house with piping underneath i'd install a external Frost Stat.

If the boiler is internal to the house, and it's well insulated with pipes internal then i'd just use the boiler Frost protection.

Thank you very much for your advice!
My boiler is in garage where is cold. And my pipes are in the loft without insulation by the installer...

So I should keep the old external frost stat to work with the boiler's internal frost protection, right?
If this is the case, then I will need to install a pipe stat on the pipe in the loft as well, right?

By the way, the pipe stat is for this function only: "Without the pipe stat the frost stat will keep cycling the boiler until the temperature around the stat creeps above its set point. " ?

I mean, if the loft is very cold, will the pipe stat tell the boiler to fire to warm up the pipes in loft?

Thank you again!

 

[Jurgenjay]

I believe this website user is someone from another thread a few weeks myself and others were collaborating with. If so the boiler is mounted in a garage.

You are right you helped a lot on the other thread for the other query.
Now, I was advised to disconnect the old external frost stat but here I have different viewpoint which sounds reasonable.

I believe you gave your opinion on pipe stat as below:

"I'm not gas certified, or have any experience with gas boilers, so can't say how they like to behave. However on oil boilers with a frost stat you have a pipe stat wired in series with the frost stat to bring the CH on. When the frost senses say 5⁰c it sends a feed to the pipe stat, the pipe stat is set to cut power when it senses a temperature of between 10-20⁰c. The pipe stat is wired into the CH zone valve by-passing the room stat. By doing it this way you only bring the boiler on to take the chill off it and the system to prevent potential freezing. Without the pipe stat the frost stat will keep cycling the boiler until the temperature around the stat creeps above its set point. Obviously in a garage with large heat loss you may never get the temperature in the room above the stat set point."

I understand from the above that the pipe stat works with external frost stat to stop boiler keeping firing.

My question is: if the loft is very cold, will the pipe stat tell the boiler to fire to warm up the pipes in loft? (apart from working with external frost stat to stop boiler keeping firing)

 

[Last Plumber]

My question is: if the loft is very cold, will the pipe stat tell the boiler to fire to warm up the pipes in loft? (apart from working with external frost stat to stop boiler keeping firing)

Not on its own. The supply to the pipe stat in this suggestion comes via the frost stat so it cannot provide a switched live without the frost stat being closed, even if the pipe stat closes.

Each installation needs to be taken on its own merits. In some circumstances it is enough to site a frost stat above pipework to be protected. That tends to be OK if pipes are run along a wall for example.

If you intend to follow this idea, it sounds like it might be better to site the frost stat in the loft as well as the pipe stat?

 

[Jurgenjay]

Not on its own. The supply to the pipe stat in this suggestion comes via the frost stat so it cannot provide a switched live without the frost stat being closed, even if the pipe stat closes.

Each installation needs to be taken on its own merits. In some circumstances it is enough to site a frost stat above pipework to be protected. That tends to be OK if pipes are run along a wall for example.

If you intend to follow this idea, it sounds like it might be better to site the frost stat in the loft as well as the pipe stat?

Thank you!

So to ensure I understand you correctly, your points are:
1, The pipe stat (my pipes are in the loft) on its own can not tell boiler to fire if the loft is too cold; the pipe stat can only work with frost stat installed in garage where my boiler is now.
2, If I want to protect the pipes being frozen in the loft, I will need to install a frost stat and pipe stat together in the loft?---Apart from one frost stat wired to boiler in the garage already (also the new boiler has internal frost protection)

 

[Last Plumber]

The internal boiler protection only monitors and protects the boiler. You still need additional protection for the system/pipework if necessary.

Here read this link.

I have not seen a pipe stat with a low enough setting to act alone as frost protection (doesn't mean they don't exist) so I think you would need both air and pipe stats.

If the loft is well lagged so that the pipes are exposed to cold above the lagging, then that may be the coldest place in the house? only you will know that. It will work with the frost stat in the garage and pipe stat on the pipe in the loft (return) but it might be better if the loft gets colder quicker than the garage for it to be up there. Does that make sense?

Think more along the lines of what you would do if the existing stat (garage) wasn't there and you were starting from scratch, how would you best protect it from freezing?

 

[Jurgenjay]

The internal boiler protection only monitors and protects the boiler. You still need additional protection for the system/pipework if necessary.

Here read this link.

I have not seen a pipe stat with a low enough setting to act alone as frost protection (doesn't mean they don't exist) so I think you would need both air and pipe stats.

If the loft is well lagged so that the pipes are exposed to cold above the lagging, then that may be the coldest place in the house? only you will know that. It will work with the frost stat in the garage and pipe stat on the pipe in the loft (return) but it might be better if the loft gets colder quicker than the garage for it to be up there. Does that make sense?

Think more along the lines of what you would do if the existing stat (garage) wasn't there and you were starting from scratch, how would you best protect it from freezing?

Thank you again for your advice!

I understand I need pipe stat in the loft to work with existing external frost stat next to boiler in the garage; air stat you mean the external frost stat but to install in the loft, similarly to the existing frost stat in the garage, right?

My loft is not well lagged, and the pipes are exposed to the cold, so yes probably it is the coldest place in the house.
I am not sure I understand "but it might be better if the loft gets colder quicker than the garage for it to be up there"---does this mean, only the loft is colder than the garage, then the to be installed loft frost stat will work properly?

 

[Last Plumber]

Thank you again for your advice!

I understand I need pipe stat in the loft to work with existing external frost stat next to boiler in the garage; air stat you mean the external frost stat but to install in the loft, similarly to the existing frost stat in the garage, right?

My loft is not well lagged, and the pipes are exposed to the cold, so yes probably it is the coldest place in the house.
I am not sure I understand "but it might be better if the loft gets colder quicker than the garage for it to be up there"---does this mean, only the loft is colder than the garage, then the to be installed loft frost stat will work properly?

I meant that if the loft is colder than the garage or gets coldest first, then the frost stat might be better off up there as opposed to in the garage. The pipes you are most concerned about are up there and i presume this is an attached garage. Attached garages are not normally subject to freezing conditions due to heat loss from the house.

 

[Jurgenjay]

I meant that if the loft is colder than the garage or gets coldest first, then the frost stat might be better off up there as opposed to in the garage. The pipes you are most concerned about are up there and i presume this is an attached garage. Attached garages are not normally subject to freezing conditions due to heat loss from the house.

I meant that if the loft is colder than the garage or gets coldest first, then the frost stat might be better off up there as opposed to in the garage. The pipes you are most concerned about are up there and i presume this is an attached garage. Attached garages are not normally subject to freezing conditions due to heat loss from the house.

You are right that the garage is attached in the house.
So should I install a frost stat in the loft?
And keep the existing garage frost stat (and to install a pipe stat to work with this garage frost stat?)

Is this normally people do when their boiler locates in garage, and they have a loft with pipes there?

Thanks again!

 

[Last Plumber]

You are right that the garage is attached in the house.
So should I install a frost stat in the loft?
And keep the existing garage frost stat (and to install a pipe stat to work with this garage frost stat?)

Is this normally people do when their boiler locates in garage, and they have a loft with pipes there?

Thanks again!

It is something I would assess on site normally.
I personally have never used a pipe stat/frost stat combination and I have been at it going on 35 years now.
If the garage gets cold enough to close the stat, then it'll be OK. Once the pump kicks in, the water is moving so it won't freeze. The pipe stat idea is a good one from an efficiency point of view because it will turn the boiler off once a bit of heat gets round.
If you think the garage stat will work when it gets below say 3 degrees outside, that'll do it. If it never gets cold enough in the garage, stick it in the loft. If you can site it over the pipes, that'll do, if not use a pipe stat with it.

 

[Jurgenjay]

It is something I would assess on site normally.
I personally have never used a pipe stat/frost stat combination and I have been at it going on 35 years now.
If the garage gets cold enough to close the stat, then it'll be OK. Once the pump kicks in, the water is moving so it won't freeze. The pipe stat idea is a good one from an efficiency point of view because it will turn the boiler off once a bit of heat gets round.
If you think the garage stat will work when it gets below say 3 degrees outside, that'll do it. If it never gets cold enough in the garage, stick it in the loft. If you can site it over the pipes, that'll do, if not use a pipe stat with it.

I agree that it's better to assess it on site! I hope someone like you who knows this kind of work to come on site to check to ensure the best way to do it, but you are based in Lancashire, I am down in Dorset which is too far for you....

Did you mean you never used pipe stat and frost stat together? You mentioned earlier "It will work with the frost stat in the garage and pipe stat on the pipe in the loft (return)".

I tracked the temperature actually, on 21st of January this year, the outside was coldest day with -6 degree, the garage was 6 degree, the zone valve for HW opened and the boiler started to fire for nearly 4 hours. I assume it was because the garage frost stat acted?

So based on the last paragraph you said, normally there are NOT two frost stats (one in garage, one in loft) installed in the same house? Either frost stat in garage (if colder) or in loft (if colder)?
If stick with garage frost stat, then I will need a pipe stat in the loft with it together?
If install a frost stat in loft, then do I need pipe stat?

 

[Last Plumber]

It might be best for you to ask a heating engineer to sort out your frost protection. They will assess it properly and it isn't a big job to sort it by the sounds of it. That way you will know it's as good as it needs to be.

 

[Jurgenjay]

It might be best for you to ask a heating engineer to sort out your frost protection. They will assess it properly and it isn't a big job to sort it by the sounds of it. That way you will know it's as good as it needs to be.

Thanks a lot for all your advice!