Fireplace chimney question

[akrawitz]

I am a complete chimney newbie. I have tried to search for relevant info, but have been unsuccessful - perhaps because I don't know the correct terminology. Thanks in advance for any help you can give.

The question is:
Why does there seem to be outside air flowing out of the bottom of the chimney and into the area, behind the interior wall, where the firebox is?

Now for more explanation to hopefully clarify this question:
We have a fireplace in the basement of our (rented) condo. It is in a corner, on a diagonal to the walls. The installation around the fireplace opening is stone, but above the mantel it is just drywall. Due to a pipe freezing and busting, the drywall above the fireplace has been temporarily removed for repair work. The firebox is sitting in the triangular space formed by the two perpendicular walls of the room, and the front of the fireplace which runs from one wall to the other on a diagonal. When I look over the mantle, I can see the metal chimney pipe descending down and connecting to the top of the metal firebox. It looks as if there is a 2-3" gap between the bottom of the chimney pipe and the top of the fireplace. I don't mean that it is loose or something, but that it is designed that way. Presumably there is an interior wall within the pipe that doesn't have this gap, but I can't see this directly. In any case, when I put my hand down next to this gap, I can feel what certainly seems to be freezing cold outside air blowing into the room. Indeed, the entire basement has been quite cold since they removed the drywall. Of course, once they replace the drywall, this area will be sealed from the room, but it still seems strange to be piping outside air into this space which is seperated from the living area by only drywall. No doubt, this contributed to the pipe freezing back behind the wall despite the house being heated. Is this arrangement normal? Why would cold air be coming out the bottom of the chimney pipe like that? Why would the pipe have an opening into this enclosed space at all?

I should add, the flue is closed, and we have never actually used the fireplace (I know this won't make me popular on this forum!).

I can post pictures if that would help clarify the situation.

Thanks again for any help you can give,
adam

 

[73blazer]

What brand and model of fireplace is it?

My bet is it is double wall air cooled, probably heatiltor (or Heat n' Glo, or Quadrafire) SL300 air cooled pipe.
My bet also is it's a heatnglo or heatilator builder special model, and they choose not to install what is called the chimney air kit.
The chimney air kit connects to the bottom portion of SL300 pipe to the outside (again, only for heatilator or heatnglo or one quadrafire model) and is designed to pull outside air up thru the outer cavity of the 2 chimney pipes. Since htere is no chimney air kit on yours, your house is acting as a chimney and you have negative air pulling back thru that pipe, cause your cold air infiltration. On builder models in the US, the chimney air kit is optional.
There should be a brand/model on the fireplace (a little plaque inside, or on a beaded chain underneath, somewhere from the front or inside the firebox telling you this. You might also see some labels on the chimney pipe itself, like SL348 or SL324 or something like that.