pipe stat on gunbarrel? Solid fuel stove boiling.

LostInLM

A few years back a solid fuel stove was installed in the house replacing a previous back boiler in the fireplace. It was plumbed into existing gunbarrel pipes which go up into the attic and across the ceiling before going back down to the hot press in the hall where there is an open cylinder circuit and a pumped circuit to distribute to some of the rads. There is a pipe stat up in the attic on the flow from the boiler just after where it turn across the ceiling. It is set to 40 degrees.

Recently, if there is a big fire in the stove the water has started to boil and vent steam off the air valve. It would appear the pipe stat is not switching on the pump even though the pipes coming out of the boiler are very hot near the stove. I haven't got up to the attic to see if they are hot up there.

Other times with a slower fire everything works as normal. The pump kicks in at and lets heat out to the rads.

To temporarily resolve it, I took the stat out of the wiring circuit and activate the pump using the isolation switch. This worked fine and the venting stopped and heat went out to the rads. Only problem is that pump is not in a great location in the hot press (covered with clothes!) and don't like the idea of keeping it permanently on. Once it started pumping I can see that the pipe stat switched on.

To resolve, I'm thinking of replacing the pipe stat and putting it nearer to the stove down in the room. However i'm wondering if there may be something else at play. Is it possible for water to be near boiling down at the stove but gunbarrel pipe up ~2m in the attic not sufficiently warm to activate the stat?

What do people think? Is this common, or should I get someone in to take a deeper look?

upupup

LostInLM wrote: »

A few years back a solid fuel stove was installed in the house replacing a previous back boiler in the fireplace. It was plumbed into existing gunbarrel pipes which go up into the attic and across the ceiling before going back down to the hot press in the hall where there is an open cylinder circuit and a pumped circuit to distribute to some of the rads. There is a pipe stat up in the attic on the flow from the boiler just after where it turn across the ceiling. It is set to 40 degrees.

Recently, if there is a big fire in the stove the water has started to boil and vent steam off the air valve. It would appear the pipe stat is not switching on the pump even though the pipes coming out of the boiler are very hot near the stove. I haven't got up to the attic to see if they are hot up there.

Other times with a slower fire everything works as normal. The pump kicks in at and lets heat out to the rads.

To temporarily resolve it, I took the stat out of the wiring circuit and activate the pump using the isolation switch. This worked fine and the venting stopped and heat went out to the rads. Only problem is that pump is not in a great location in the hot press (covered with clothes!) and don't like the idea of keeping it permanently on. Once it started pumping I can see that the pipe stat switched on.

To resolve, I'm thinking of replacing the pipe stat and putting it nearer to the stove down in the room. However i'm wondering if there may be something else at play. Is it possible for water to be near boiling down at the stove but gunbarrel pipe up ~2m in the attic not sufficiently warm to activate the stat?

What do people think? Is this common, or should I get someone in to take a deeper look?

The stat should be within a meter of the stove with copper so i think 2 meters with gunbarrel is too far.
The best direction for the water from stove to hot press is up,, so any horizontal run like you have in the attic can cause airlock problems. that may be the problem especially since the stat is on the horizontal run in the attic as the hot water may have trouble getting around that bend.an air valve at that bend would help too.

LostInLM

upupup wrote: »

The stat should be within a meter of the stove with copper so i think 2 meters with gunbarrel is too far.
The best direction for the water from stove to hot press is up,, so any horizontal run like you have in the attic can cause airlock problems. that may be the problem especially since the stat is on the horizontal run in the attic as the hot water may have trouble getting around that bend.an air valve at that bend would help too.

Thanks for the input. I had a closer look in the attic and the pipe from stove rises ~30cm as it crosses the attic before dropping to cylinder at hotpress. Also it vents to the tank there. Assume that is by design to avoid airlocks. I'll move the stat anyway and see if it helps.

Another thing I was wondering about is whether immersion heating cylinder up before fire is lit is somehow preventing gravity flow.

upupup

LostInLM wrote: »

Thanks for the input. I had a closer look in the attic and the pipe from stove rises ~30cm as it crosses the attic before dropping to cylinder at hotpress. Also it vents to the tank there. Assume that is by design to avoid airlocks. I'll move the stat anyway and see if it helps.

Another thing I was wondering about is whether immersion heating cylinder up before fire is lit is somehow preventing gravity flow.

The layout of the pipes in your attic seem fine.
When the stove water is cold and the cylinder water is hot because of the immersion,then(i think) gravity flow will reverse.the water in the cylinder coil will warm and rise and then fall back to the stove which may cause a little resistance to the stove water as it tries to rise.

Dtp1979

upupup wrote: »

The layout of the pipes in your attic seem fine.
When the stove water is cold and the cylinder water is hot because of the immersion,then(i think) gravity flow will reverse.the water in the cylinder coil will warm and rise and then fall back to the stove which may cause a little resistance to the stove water as it tries to rise.

Only if there’s 2 pipes rising. How long is the horizontal run? Is the cylinder higher than the stove?