Replies

1. 
   Wet_Head | Aug 19, 2002 07:41pm | #1

   Each unit is different.  Call your installer for the specs you need.

1. 
   FTDFlooring | Aug 20, 2002 01:23am | #2

   Thanks,

   The house is 6 years old. I have no idea who the installer was. Any further suggestions would be greatly appreciated.

   Thanks

1. 
   rjw | Aug 20, 2002 01:48am | #3

   Most codes (e.g., the mechanical code) call for 1 sq in of free vent space for every 1,000 BTU of input capacity.  That space has to be divided high and low.

   So, if you have 100,000 btu furnace, you need 100 square inches of free vent space.  Say your 10 x 10 return type grill has a free vent space of 50%, you need 2 of those 10 x 10. Put one toward the top of the wall, one toward the bottom.

   Now, that's assuming the return duct in the furnace space is prefectly sealed (i.e., doesn't try to draw any of the combustion air into the return plenum.)  Seal it up as well as you can and give yourself some excess capacity.

   Is it important?  YES!  A good furnace technician will red tag / disable a furnace with insufficient compbustion air because it can cause dangerous CO conditions (and mess up the furnace, as well.)

   Don't forget to have the furnace serviced evry year.  Wouldn't be a bad idea to get your heating technician to advice on the best way to provide combustion air for your situation.

   Oh, yeah: don't forget to maintain adequate clearnaces for the flue (6" for single wall; 1" for double wall B-vent) away from any combustible material (framing or other lumber, drywall (has paper liner) etc.   Might not catch fire today, but could a few years down the road due to pyrolysis.

   Edited 8/19/2002 6:51:47 PM ET by Bob Walker