Hi Jason, This is an old fireplace that is brick and masonry. When I look up the chimney I see the long rectangular metal damper door that pivots in the middle, and two pull chains [or linked pull rods] on the left and right that open and close the damper door by flipping it from horizontal to vertical like a big carberator choke. The area below the damper is 52"x17". How can I size a Chimney Balloon for this type of fireplace? - AE
Hi AE, From looking at the photo it looks like the damper is set up about 12 inches vertically above the termination of the lintel. This will give you enough room to put a large chimney balloon under the damper. I see the walls taper some on the sides, but are ressonable straight up and down in the front and back.
I recommend we go with a custom size 52"x17" chimney balloon below the damper. As you inflate the balloon the chains will be pushed off to the side and the balloon will seal around them.
BTW, you are going to want a pump to inflate this 52x17 Chimney Balloon. It takes a lot of air to fill a balloon of this size. - Jason
***three weeks later***
After I inflated it I noticed that about 2 inches of the belly of the balloon is still visable below the lintel, but since the balloon is clear it is not very noticable. Especially since I keep the chain spark screen closed anyway. This isnt going to negatively effect the seal the balloon offers, is it? - AE
Hi AE, This large of a custom balloon will be about 12 inches tall when inflated, so it is not too surprising is portrudes below the lintel a bit. However, the balloon is clear and the firepalce is dark so you wont notice it.
And, no the seal will not be effected by the chimney balloon hanging down below the lintel a few inches. The contact seal will be on the upper side of the balloon anyway. If you use a strong flashlight to look through the balloon, you will see how the balloon sealed to the walls.
Godo Job BTW with the measurements and the install. You handled that application like a pro! - Jason