How crucial is using outside air for combustion?

[kilarney]

I just ordered a Harman Accentra insert. I noticed that you can run a 3" pipe just past the flue to draw in outside air for combustion. This is adjacent to the 4" exhaust pipe.

Just how important is this to efficiency? Obviously, if you use inside air for combustion and blow the exhaust outside of the house, you have to draw air into the house to replace it. That's going to be cold air coming in.

I'm a little nervous because the dealer didn't seem to install the inserts in this manner. They were going to look at the manual and get back to me.

I think that I will tell them that this is the only way that I will have it installed.

Am I just being crazy, or is it important to use outside air for combustion?

 

[STOVEGUY11]

Harmans do not require outside air adaptors. If its a tight house, or a small area I would consider it though.

 

[kilarney]

It's an older house. It's not drafty, but I wouldn't call it tight.

I guess I'm mostly concerned about how much efficiency I'd be losing. Any idea?

 

[STOVEGUY11]

Im not sure your going to be able to really get an exact number. Pellet stoves are not even efficieny rated. I would say if you really want the outside air, then have the dealer install it.

 

[Dougsey]

kilarney, Also consider that you'll be drawing cold ouside air through your stove which, in theory, would also lower efficiency.

 

[kilarney]

How would that lower efficiency? The air would just get blown back outside.

 

[Dougsey]

You're pulling 20* air through the stove instead of 70*. I would think the stove would burn slightly more pellets to compensate.

 

[kilarney]

True, the air in the combustion chamber would be colder.

The air that is blown into the room would come in at 70 degrees, though.

Keep in mind, the air that is blown into the room as heated air never comes into contact with the air that is in the combustion chamber.

So what do people think?

Am I making something out of nothing?

 

[kilarney]

I just had another concern.

The intake for the air sits just above the flue for the fireplace in the chimney. Therefore, it draws in outside air via the chimney.

If the chimney is capped, this seems to pose a problem. More importantly, if the exhaust is coming from the terminus of the chimney, won't this just suck in air that's heavy with exhaust?

 

[kilarney]

Nevermind! I see that Harman sells and adjustable chimney intake extension that takes care of this.