Furnace room warm after closing off

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Old 11-09-08, 10:32 AM
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Furnace room warm after closing off

I recently finished my basement and closed off my furnace room. There is a single bi-fold closet door(not louvered) to allow entrance into the furnace room. The room gets very warm as there is a natural gas furnace and a gas heated water tank. There is fresh air intake from outside into the room. The city said my setup was ok, but I would like some other opinions. My carbon monoxide detectors have not chirped yet(1.5 months since project completion). However, when the A/C runs(fan is on high), the bifold door will open up from pressure...?

 
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Old 11-10-08, 07:47 AM
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Originally Posted by n0c7 View Post
The room gets very warm as there is a natural gas furnace and a gas heated water tank.

However, when the A/C runs(fan is on high), the bifold door will open up from pressure...?
Sounds like you got a big leak or a lot of it in your ductwork if the door is blowing open!
 
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Old 11-10-08, 08:16 AM
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Originally Posted by Jay11J View Post
Sounds like you got a big leak or a lot of it in your ductwork if the door is blowing open!
Well, I do have an office rest next to the furnace room with a return air in the ceiling. Maybe that's whats pulling it? And its just opening it a bit where the split is. About the same tension as a regular door being pulled closed when the system runs. I just find it odd it only happens with the A/C runs and not when the heat runs.
 
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Old 11-10-08, 08:23 AM
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Originally Posted by n0c7 View Post
Well, I do have an office rest next to the furnace room with a return air in the ceiling. Maybe that's whats pulling it?
Maybe, but i would not block off the return, just need to seal the duct of what you can see/feel for leaks.

The room itself will be warm from the heat of the water heater, and furnace.


I just find it odd it only happens with the A/C runs and not when the heat runs.
The blower in heat mode most of the time runs slower than in cool mode.
 
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Old 11-10-08, 09:21 AM
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Yeah now that you mention it, when the A/C runs there is alot more air pressure coming out of the vents and the furnace is louder. It must run on high speed with A/C and a lower speed with heat.

I had my basement inspected by the city and from what he could tell everything looked ok. One concern I do have however is that I built on the office to the furnace room. You have to enter the office, which is 7x7 feet(roughly) and has a 30in door. To get into the furnace room from the office, there is the 36in bifold door seen above. I placed the return air in the office in the furthest corner away from the furnace.

If I close the door to the office and open the bi-fold closet door(not a likely situation but it could happen) will there be an issue with the return air duct sucking in anything? I've read that you should not have a return air duct in the furnace room. Essentially its not, but with the doors closed/open in that order, its kind of making the office part of the furnace room. The return duct is approximately 8 feet away from the furnace and in the ceiling.

I'm running two brand new CO detectors, one in the furnace room and one on the second floor of the house where the bedrooms are. They have yet to show any reading past 0PPM but I'm paranoid and want to avoid any possible hazardous situations.
 
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Old 11-10-08, 11:52 AM
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Seeing your photo you got fresh air on the right side, and I can't see what you have for furnace, do you have a newer 90% furnace? (use two PVC pipe going outside)
 
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Old 11-10-08, 12:01 PM
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Originally Posted by Jay11J View Post
Seeing your photo you got fresh air on the right side, and I can't see what you have for furnace, do you have a newer 90% furnace? (use two PVC pipe going outside)
The home was built in 2004 and its a Goodman furnace. The manual says its "high efficiency" but I'm not sure what percentage. Here is the best picture I could take to show you the ducting. Please ignore the junk in there(the paint cans.... ugh) I'm cleaning out the room today. The funny looking U pipe with the thermal tape is my hot air run to the office, it was the only way I could make it work and since its such a short distance I wasn't too concerned with heat loss.

 
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Old 11-10-08, 04:00 PM
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That an 80% furnace.. I am kinda suprised to see that in that new of home and that far up north.. Here in Minnesota, 90% has to be in new homes, and been like that about the last 10 years.

Couldn't see much of the main duct in the photo, but run your hands on the joints/seems, and feel for draft.. If there's a major leak, then get some duct mastic to seal off the leaks.

Also, you could add a dummy return grill between the furnace and office room to allow the pressure to get out of the room.
 
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Old 11-10-08, 04:31 PM
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Based on what you see, is my air intake for combustion air adequate? The city thinks so... As for the dummy grill, if the door keeps driving me nuts in the summer, I'll definitely do this.

Out here, you get what you pay for. This was our first house, didn't know too much at the time and I would definitely go for a Carrier high efficiency the next time.
 
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Old 11-10-08, 09:47 PM
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My only real question left is - with a fresh air supply that goes into the furnace, and another that dumps to the floor with a 6" pipe, is it really necessary to cut grills in high and low to the furnace room? My city says no, but from reading online some cities in the states say yes.
 
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Old 11-10-08, 10:06 PM
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I would cut it high, that way you won't get the cold spill from the floor.
 
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Old 11-10-08, 10:45 PM
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Do you think I even need to bother cutting in a high one or is my fresh air supply adequate? (6in diameter each).
 
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Old 11-11-08, 07:49 AM
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Your 6" is enough.. The grill is use to let the pressure out of the room so the door don't open up on you.
 
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Old 11-11-08, 09:29 AM
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I've spoke with some other people and they gave me this calculation:

If your total btu's are 126000 and you are bringing all air from outside using 1 opening then it should be located within the upper 12" of the enclosure. For 126000 btu's and 1 opening you would need a minimum opening of 1 sq. inch per 3000 btu/h (126000 divided by 3000= 42 sq. in.) To provide 42 sq. in. for proper combustion you would need a 8 inch round opening ( a 6 in. is only adequate for 28.27 sq. in).

Now my furnace is 90,000 input BTU and the hot water tank is 36,000 input BTU. What do you take on this quote?
 
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Old 11-11-08, 06:03 PM
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If your furnace and water heater has been running fine for the last 4 years with this fresh air set up, I wouldn't worry about it..

Chances are, you have air leaking into your home else where, otherwise, You would of had a reading on your CO alarm.
 
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Old 11-11-08, 06:29 PM
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I only recently finished the basement, its been boxed off for 1.5 months with the doors installed. Just getting through all the things I overlooked and now that its winter time here the furnace will be running alot.
 
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