PE Summit Short Cycle Question

[Richmond84]

Hello there, new member here. I have a question about a PE Summit LE Insert that I had installed last fall.

I did what I thought was ample research into the combustion air, but there's more to it than what I initially thought. I had a full SS liner put into the masonry chimney with a rain cap on top. Combustion air enters the fire box from the front and the back of the chimney has an ash cleanout that is currently closed. The back of the chimney sits in a hallway for two recently finished bedrooms (used to be the garage).

When burning last winter, I could feel the supply air coming from the top of the stove and being directed straight into the floor in front of the unit. Seemed fine at first until I felt the stream of colder air running straight through this supply and back into the firebox where it is wastefully being sent up and out the flue. The manual shows supply air flowing up and away from the unit, not into the floor. The heat output seems less than what it should produce. Is this normal? Should I be pulling the combustion air from the ash cleanout in the back and block off the front, and if so, what about the "boost air" that the manual calls for? I added some pictures for clarification. Any thoughts are appreciated!

Alan

 

[kennyp2339]

What your feeling is a mixture of room air being used for combustion and room air going through its convective cycle (cold air heats up, expands and flows outwards, cools off and sinks, heads back to the stove again.
I think your kind of stuck with using room air as combustion air since your don't have a direct path from the ash dump in the fireplace to the outside atmosphere.
But if you did have a direct path for outside air, your could remove the ash dump flap, place a mesh screen over the hole, make sure the front face plate is on under the ash lip (seals off the room air supply) install a block off plate (its a good idea to do that anyway) and seal around the surround to ensure your pull main combustion air from the old ash dump.

 

[Richmond84]

What your feeling is a mixture of room air being used for combustion and room air going through its convective cycle (cold air heats up, expands and flows outwards, cools off and sinks, heads back to the stove again.
I think your kind of stuck with using room air as combustion air since your don't have a direct path from the ash dump in the fireplace to the outside atmosphere.
But if you did have a direct path for outside air, your could remove the ash dump flap, place a mesh screen over the hole, make sure the front face plate is on under the ash lip (seals off the room air supply) install a block off plate (its a good idea to do that anyway) and seal around the surround to ensure your pull main combustion air from the old ash dump.

Thanks for the quick reply! It's like you read my mind, I'm planning to do all those things before the next burning season. I don't think it would hurt anything to pull air from the back side as long as the door is removed and a mesh screen installed. Alternatively I can bust a hole in the chimney in the attic and pull combustion air from there.

My hope is to pull combustion air, even when it doesn't matter much as the damper is closed off, from a place that doesn't send heated air back up the chimney.

 

[Richmond84]

That still begs the question though; why would Pacific Energy design a stove to exhaust expensive heated air in the same channel that combustion air is going? Does pre-heating the air make it more efficient so it's EPA compliant or something?

 

[begreen]

Unless a stove has an OAK connection it is burning heated room air. Where else would it get it from? The volume is not large. I suspect that they chose for the convection air to be deflected down low to better mix with the colder room air down by one's feet. That should provide a more comfortable and even heating experience.

 

[kennyp2339]

That still begs the question though; why would Pacific Energy design a stove to exhaust expensive heated air in the same channel that combustion air is going? Does pre-heating the air make it more efficient so it's EPA compliant or something?

I think your getting 2 different things mixed up with that, you have primary air and secondary combustion air, the primary air will either enter through the front face plate under the ash dump flap, or channel through the rear of the unit to the front and into the stove, the secondary air takes a similar path but then gets routed through a metal channel were it gets heated by the main fire and sent through the tubes in the baffle to agitate the and reburn the unburnt smoke particles from the main fire to get cleaner combustion, all exhaust then leaves the fire box by going up and over the baffle and out the flue collar. The other arrows in that diagram that you posted are showing convective heat that stays on the outside of the fire box (goes through the insert jacket) and out the front with fan assistance, and radiant heat from the large viewing glass.
As far as punching a hole in the chimney at the attic area for a oak, it would be wise not do that, while its a remote possibility , you can depending on chimney draft and whether the chimney liner gets plugged, you can reverse your draft and cause hot gases to flow out your intake and into the chimney then through the hole cause big issues, like fire or co poisoning. All oak's need to be level or below level with the stove.

 

[begreen]

As far as punching a hole in the chimney at the attic area for a oak, it would be wise not do that, while its a remote possibility , you can depending on chimney draft and whether the chimney liner gets plugged, you can reverse your draft and cause hot gases to flow out your intake and into the chimney then through the hole cause big issues, like fire or co poisoning. All oak's need to be level or below level with the stove.

Thanks Kenny. Definitely don't do that.

 

[Richmond84]

Unless a stove has an OAK connection it is burning heated room air. Where else would it get it from? The volume is not large. I suspect that they chose for the convection air to be deflected down low to better mix with the colder room air down by one's feet. That should provide a more comfortable and even heating experience.

Sounds reasonable enough, thank you for the response. I must be overthinking it but in my mind, air on the back of the chimney is heated to around 70F while the path in the front is likely much higher due to the blower discharge. Like you said, the volume is not large when the damper is low.

 

[Hogwildz]

I think what you are feeling is the cooler air traveling to the stove while the stove is releasing heated air. This is the convection loop. The actual combustion air is very minimal. Make sure a block off plate was installed around the damper area. Many complaints stem from no block off plate and a ton of heat going up while allowing cold air to drop down into the living space.

 

[Richmond84]

I think your getting 2 different things mixed up with that, you have primary air and secondary combustion air, the primary air will either enter through the front face plate under the ash dump flap, or channel through the rear of the unit to the front and into the stove, the secondary air takes a similar path but then gets routed through a metal channel were it gets heated by the main fire and sent through the tubes in the baffle to agitate the and reburn the unburnt smoke particles from the main fire to get cleaner combustion, all exhaust then leaves the fire box by going up and over the baffle and out the flue collar. The other arrows in that diagram that you posted are showing convective heat that stays on the outside of the fire box (goes through the insert jacket) and out the front with fan assistance, and radiant heat from the large viewing glass.
As far as punching a hole in the chimney at the attic area for a oak, it would be wise not do that, while its a remote possibility , you can depending on chimney draft and whether the chimney liner gets plugged, you can reverse your draft and cause hot gases to flow out your intake and into the chimney then through the hole cause big issues, like fire or co poisoning. All oak's need to be level or below level with the stove.

Oh come on, what’s life without a little risk? But seriously though, didn’t know about that. I’d rather not make the evening news. Thanks for sharing.

 

[Richmond84]

I think what you are feeling is the cooler air traveling to the stove while the stove is releasing heated air. This is the convection loop. The actual combustion air is very minimal. Make sure a block off plate was installed around the damper area. Many complaints stem from no block off plate and a ton of heat going up while allowing cold air to drop down into the living space.

That’s the second time today I’ve heard about a block off plate. There isn’t one but it’s within my purview to make one. So even if half the chimney is in the house it still makes a difference?

 

[Richmond84]

Thanks Kenny. Definitely don't do that.

Good to know, thank you!

 

[begreen]

With an interior fireplace a lot of the heat loss to the surrounding masonry will slowly be released into the house as opposed to outdoors with an exterior fireplace. So a block-off plate in an interior fireplace will make less of a difference, especially if the fireplace is central and the masonry is exposed on all sides. If one is put in, there will still be some gain in convective heat output though by increasing the temp around the convective jacket of the insert.

 

[Richmond84]

With an interior fireplace a lot of the heat loss to the surrounding masonry will slowly be released into the house as opposed to outdoors with an exterior fireplace. So a block-off plate in an interior fireplace will make less of a difference, especially if the fireplace is central and the masonry is exposed on all sides. If one is put in, there will still be some gain in convective heat output though by increasing the temp around the convective jacket of the insert.

About 2/3 of the chimney is still exterior to the house. I think it would still be time well spent to fab a block off plate.

 

[Hogwildz]

That’s the second time today I’ve heard about a block off plate. There isn’t one but it’s within my purview to make one. So even if half the chimney is in the house it still makes a difference?

In my opinion yes. Masonry soaks up heat, and while some will go back into the living space, much will be transferred to the outside. The lack of block off plate will also let cooler/colder air in the chimney cavity to drop into the living space.