sealed furnace room

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Old 02-02-04, 09:15 AM
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sealed furnace room

I am in the process of remodeling my basement and am I am going to turn the corner of the basement where the furnace and hot water tank (both natural gas) into its own seperate room.
Anyways the room has a tube (4" diameter) running to the outside off the house for fresh air intake for the burners and chimney I guess.
1) I should have no problem making the room airtight to the rest of the basement should I?
I figure by sealing off the rest of my basement the furnace and HWT can only use the fresh air intake for combustion air and it will stop it from mixing with my already heated or cooled basement air.

2) Also I was planning on insulating at least one of the interior walls to this room to limit the sound transfer from the furnace to my TV room, is there code about putting fiberglass insulation within a certian distance of the furnace?
 
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Old 02-02-04, 09:46 AM
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I would check code there where you are for sure.Like down here some codes call for 1sq" per 1000 Btu for air to the furnace when you close it up that way . ED
 
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Old 02-02-04, 04:55 PM
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ed is right. depending on btu ratings, pipe will be almost 8 inch, one high, one 12 inches off floor
 
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Old 02-02-04, 05:41 PM
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You need to check the Nation Fuel Gas Code for all the info you are asking.
You need to know the total BTU - furnace and water heater - to figure vent size. There will be offsets built in for the type of venting you are looking at. Louvers or screening on the plenum will have an impact also.
You need to have a inlet source within 12" of ceiling and another 12" off the floor also as hvac4u stated. This is a safety type thing for mixing air in the room.

There is a chance that undersizing the air supply would cause improper burning in the furnace and heater with both going. This would be bad.

Also, if you are in a cold climate subject to freezing, what about protection of exposed plumbing. Having a furnace and water heater in a room does not assure warm temps in that area. You will have cold air dumpng in the room. Just a thought.

Be careful doing your calculations on the air flow.

Good luck.
 
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Old 02-02-04, 09:54 PM
binford
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There is also a min of 100sq inches, on unit less than 100,000 BTU. Call the building dept, and find out if they have a handout for this type of thing, you can't be the first in your area to do this.
The building dept here has a web page with all there handouts on line.
 
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Old 02-03-04, 05:03 PM
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My total BTU is 111,000 for the furnace and the HWT, that means that I need a total of 11sq inches air intake into the room right.
currently there is a 3 inch across pipe as the air intake into the room about a foot off the ground. Using area = pi XR2 that equals 7 sq inches.
There is another 3" pipe going to an exaust fan that is going to be removed that could be opened up at the ceiling height. This would bring the total up to 14 sq inches more then enough right?

I was going to use the exaust pipe in the ceiling as a fresh air intake into the house by attaching it to the air return to the furnace and put a damper in it to control the air intake. Does this sound like a good idea? Should I maybe run a new pipe for the room air intake and use this one as my fresh air intake to the house?
 
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Old 02-03-04, 05:32 PM
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I dont think you want to take out side air and bring it into you furnace up there in Canada. Also did you ask what code is for make up air for your furnace there.?????? ED
 
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Old 02-03-04, 05:45 PM
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I havent asked what the code is yet but I am going to before I finish it. In all likely hood it is not going to be totaly sealed, there will at least be an air gap below the door for makeup air

The reason I wanted to put a fresh air intake into the furnace was because I read somewhere that due to any source of exaust (bathroom, kitchen fans etc) creates a negative air pressure and that fresh air will come in cracks around doors etc. By putting a air intake into the furnace this will give the air an easier path and condition the air and mix it with old air before it is released into the house.

Or should I leave it up to the old fashioned way of air leaking all around the house. I was going to have a damper on it so that I can shut it off on the coldest/hotest days if I wanted to, but still have fresh air come in when i want it.
 
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Old 02-03-04, 09:24 PM
binford
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go to http://www.codecheck.com/pg21_22mech...#combustionair


it is 1sq per 1000 btu's

Call the build dept and get the correct answer.. they don't ask for your and address.
 
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Old 02-04-04, 05:59 AM
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Yeah but...

ANY type of screening or louvers has to be accounted for. The raw number applies only if it is an open plenum.

And it's in Canada, they use a little different code up there (up there for me anyway).

You would be looking at a 12" pipe if pipe was used and this would be a straight run . BTW a 4" pipe and an 8" pipe does not equal a 12" pipe even for air.

Check with your local building department and ask if this would fall under tight construction with outside air, if yes, you would only need 1 air inlet instead of the 2 required for other applications. You are looking at a confined space with outside air when you are talking to your building department.

Good luck...
 
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Old 02-04-04, 09:00 AM
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Lightbulb AIR

We have tried out side air to the furnace cold air drop. Down here in MO.where its not so cold .AND its still not a good idea at all. Not worth it. ED
 
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Old 02-05-04, 10:07 AM
binford
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I miss read the IBC code. which is the IBC international building code. Reading in more detail, you find that the 1sq inch per 1000 btu is for inside air ( furnace room drawing air from adjacent room) it goes to 1sq inch per 4,000 btu for outside air and drops back down to 1sq inch per 2,000 BTU if outside air is run through a duct. You might qualify for outside air, which means you would need. 111/4 =27.75 sq inches
 
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