P2700 internal venting problem - What's wrong with this picture??

[sorka]

I've recently installed a Breckwell P2700. The combustion air intake is taken from the outisde through a PelletVent Pro exhaust/fresh air combo wall thimble. I did this to avoid the combustion air being sucked in through other sources like the fireplace flu and cooktop vent.

It became pretty evident to me that tons of cold air from the outside was making it's way into the stove and out through the convection vent on the front of the stove.

Opening up the left side of the stove, the answer was staring me plainly in the face:


I'm shocked to discover that the fresh air intake on the back of the unit does not continue through its own pipe to the damper and into the combustion chamber. Note the blue arrow. It shows the intake mixing with the main cavity of the stove. The right side of the arrow is where the air actually enters the combustion chamber, but it's pulling air from all the vents on the back of the stove as well as from outside. What's worse is that the convection blower fan(red arrow) is sucking huge amounts of air from the same chamber and in from the outside. So instead of convection blower air only coming from the inside and combustion air coming from only the outside, their mixing.

Has anyone ever complained about smoke from their Breckwell? This seems like an obvious flaw as if the vacuum in this cavity caused by the convection blower is high enough, it could over come the pull of the combustion blower and suck combusted material back and out through the convection vents.

 

[Shane]

All pellet stoves are that way. Some of them have an actual tube but it's usually perforated (check out a Whitfield). It's impossible for the scenario you mentioned to happen due to the pressure switch. The combustion blower will always pull more than the convection fan. If the combustion fan don't work the pressure switch doesn't allow the auger to feed, so there is no fire. Like I said I can't think of a single stove that has a solid intake tube.

 

[jtp10181]

Most of the stove we sell the fresh air dumps into the ash pan area underneath and then the fire draws that air in through the pot. The newest one, the Mt Vernon AE has a full gasketed and sealed ash drawer but all the others it is wide open.

 

[Corie]

I'll agree that the outside air hook up for the stove is poorly designed.

Any chance you can run your outside air pipe all the way to the collar where the slide damper is?



Shane, all of our stoves have a solid, fully welded intake tube. When you hook up outside air you truly are only connected to outside air.

 

[GVA]

as does the harman (the solid intake that is)

 

[webbie]

I can't imagine such a system (loose intake exterior air) working efficiently in very cold climates......it would seem that smoke would be less of a problem than simply offsetting the heat loss from the cold excess air - even when the stove is off. Does the outside air inlet have a damper of sorts that allows no air to flow into the stove when the stove is off?

 

[hearthtools]

A lot of stoves have a FAKE air intake
I think it is a safety for if the OAK is plugged up.

 

[Dougsey]

Shouldn't there be a tube connecting the ends of the blue arrow?

 

[sorka]

Shouldn't there be a tube connecting the ends of the blue arrow?

You would think so.

I tied a paper coffee filter(balooned with lots of surface area) to the inside of the intake(the left side of the blue line) and ran it for an hour. The stove is pulling soot from the outside since I have a horizontal termination. Not a big deal for combustion efficiency because it's probably only about 2 or 3 %, but because the stove is pulling in outside are and pushing it into the house via the convection fan, I'm getting soot in the house because of this. Not enough yet to be visible on horizontal surfaces yet as I only just fired it up for the first time.

I won't be starting it again until I bridge the gap there. I shouldn't have to worry about the convection blower not getting enough cooling air because there are 30+ square inches of venting area with the two slotted vents on the back and all of the gaps around the body of this cavity. It would be same as if I were just using internal house air for combustion and letting it be replaced by being pulled in from other sources. In fact, using it that way will be a lot more efficient given this obviously absurdly stupid design.

What's more amazing is that the installation manual says that if you're doing an outside air supply to make sure the intake path from the wall to the stove is absolutely air tight. If this blue line on the photo was a continuing pipe, then that statement would be make sense.

I can't imagine the current design is legal. The potential of pulling in exhaust from outside(like I'm actually doing in my case) and spreading it around your house would be a major health safety concern.

 

[sorka]

A lot of stoves have a FAKE air intake
I think it is a safety for if the OAK is plugged up.

Dumb question, but what is an OAK?

 

[hearthtools]

OUT SIDE AIR KIT OAK


I would dump the DV set up and do a vertical install
then you would not be pulling soot.

 

[sorka]

OUT SIDE AIR KIT OAK


I would dump the DV set up and do a vertical install
then you would not be pulling soot.

Well, it's a moot point as I won't run the stove in the current configuration which is pulling huge amounts of freezing air from the outside and blowing it directly over the exchanger tubes.

I can fix this buy either:

1) Not doing direct.
2) Bridging the gap internally.

Since I want the efficiency of DV and I already have the wall thimble for it, I'll try that first.

 

[Dougsey]

Is this design really as absurd as it seems?

What about when you close the door... is there anything to isolate the room air blower from the cold outside air?

 

[stoveguy2esw]

looking at the picture, (which is 2 dimentional so its harder to tell) is there enough room to actually bridge that gap or is the feed auger motor in the way? i cant tell from the picture. if it is you may have to use a thinwall flex pipe to make the connection. if you do , make absolutely sure that the motor terminals cannot ground to it. i agree with you , its not a great setup IMHO. as corie stated , all of our intakes when connected to an OAK are sealed systems there is no break in the tube. to me it would kinda defeat the purpose, its not direct outside air so negative pressure in the house as well as the room fan would be robbing this air.not to mention cold air leakage into the dwelling when the unit is not running unless there is a butterfly that closes when stove isnt running(this i doubt is present as there is no way the exhaust blower could possibly pull it open if there is a gap of that size present) to be blunt its a pretty dumb setup in my opinion.

 

[sorka]

There is no flap to prevent air from leaking in when it's off. But man, the amount of cold air brought in and forced into the room is huge. Enough to lower the heat exchanger vent air into the room by 10s of degrees with it being as warm as 55 F outside currently. Can't wait to see just how much difference it makes again at night and when it's freezing outside(after this current rain storm ends).

As for the auger motor connections, they're not very close to the path. In fact, if I were to get a piece of pipe cut of the same size, there'd be pleanty of room to bridge it in.

So am I correct in assuming that as long as the convection motor is running that the combustion motor must also be running? Otherwise the convection blower would easily suck soot right back out of the damper intake as well?

 

[hearthtools]

most Whifields are this way
but some of them have a square tube going to the firebox and they have a Large hole on the side of it so it still uses INSIDE make up air.

I think (not Sure) some breckwells just have a round collar on the back panel to connect a OAK


I just check some stoves in my show room
the Enviro Empress and Mini just has a collar on the back pannel
the Austroflamm just has a collar on the back also

So it is not that ODD

The enviro meridian has a Tube going all the way to the back of the Fire box but not sure if it has a hole in the side for make up air like the Whitfield.

The Avalon astoria has a tube running the whole way

 

[sorka]

The thing I don't get is that there are slotted vents all along the back and big gaps along the tops sides and bottom of the back panel and big gaps along the bottom and sides of the side panels. There's a *lot* venting of this cavity to the room. Given this, I can't imagine why the fresh air intake isn't sealed from the outside. If not using an OAK, then it's moot either way as both combustion and convection will be using the same air source no matter what you do.

 

[pegdot]

Sorka, I happen to have an older, 1991, Breckwell insert sitting on saw horses outside so I went and checked it after reading your post. Granted there's a lot of age difference but mine has a solid, no holes, pipe running from the back of the insert into the combustion chamber with a manual damper. So, I'm wondering if perhaps your stove left the factory unfinished. Have you contacted Breckwell or your dealer about this to see if it's a normal design feature or a mistake?

I believe that Breckwell had a problem with some of the convection fans on their older units. Perhaps this set up is their solution? :-/

 

[cantman]

Sorka... Is it possible the manufacturer did this for the right reason? What I'm pointing to is this split design.
I'll call them support flanges. What is the inside diameter of these flanges? Are they the same? If they are the
same diameter and linearly aligned (straight line), why couldn't you find a rigid (non combustible) pipe to slip right
through both of them. Seal them up with RTV high temp silicone, and use the area where the new pipe comes
through the back of the stove to attach your outside air kit to.

 

[hearthtools]

Sorka, I happen to have an older, 1991, Breckwell insert sitting on saw horses outside so I went and checked it after reading your post. Granted there's a lot of age difference but mine has a solid, no holes, pipe running from the back of the insert into the combustion chamber with a manual damper. So, I'm wondering if perhaps your stove left the factory unfinished. Have you contacted Breckwell or your dealer about this to see if it's a normal design feature or a mistake?

I believe that Breckwell had a problem with some of the convection fans on their older units. Perhaps this set up is their solution? :-/

No they did not forget to finish it.

Like my post above
A LOT OF PELLET STOVE HAVE THE OAK CONNECTION as just a collar on the back of the stove.

 

[hearthtools]

OH
This is why I dont believe in out side air unless it is absolutely necessary.
I dont direct vent pellets stoves I will only vertical vent ALL pellet stoves.
so Smoke back in not an issue with my installs.

I feel with a pellet stove to much moisture is be brought into the stove with outsite air.

 

[schmeg]

I'm a newb considering purchacing this stove for a doublwide. What is meant by verticle vent only? I plan on venting mine up a factory installed fireplace that has a steel lined flue and chimney up through the roof (standard mobile home fare) and would like to also run the OAK up this chimney if I need an OAK which I understand is recommended for doublewides.

 

[hearthtools]

Yes it would be best for you to run the 3" or 4" stainless Exhahst vent up the chimney
and 2 or 3" Outside air vent up the same chimney
seal off the top with a custom chase cap.