Air Circulation for Natural Gas Furnace


M

MD

I have a small 1000 sq. ft. house with a basement in Southwestern
Ohio. The basement has about an 8" diameter hole (covered by a flap)
in it that a handyman said was for air circulation for the Gas Furnace
that I have in the basement. Do I really need outside air from this
hole to run the furnace? Also, if the hole does serve the furnace, is
there a way I can work around it and get the air from somewhere else?
It seems very wasteful to me to have an open hole in a basement during
Ohio winters, and I would like to block the hole. Thanks,

MD
 
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M

m Ransley

If your house is fairly new with very tight construction and tyvek and
your furnace vents through a chimney it is possible you could not draft
when the dryer and motorised vents such as bath vent are on. If so test
it, but it is most likely unessesary
 
H

hallerb

at least run pipe from holew to furnace/

rather than a handyman a HVAC pro is the person to ask when getting the
furnace serviced before fall...
 
E

Edwin Pawlowski

MD said:
I have a small 1000 sq. ft. house with a basement in Southwestern
Ohio. The basement has about an 8" diameter hole (covered by a flap)
in it that a handyman said was for air circulation for the Gas Furnace
that I have in the basement. Do I really need outside air from this
hole to run the furnace? Also, if the hole does serve the furnace, is
there a way I can work around it and get the air from somewhere else?
It seems very wasteful to me to have an open hole in a basement during
Ohio winters, and I would like to block the hole. Thanks,
If it is properly installed, it is not wasteful, but saving you money.

You want to bring in combustion air from the outside. You don't want to
burn up the air you just paid to heat, then suck in more cold air through
cracks around windows and doors and have to reheat it again.

If you look at how your furnace works, you may get a better understanding of
this. There is a heat exchanger that has the flame on one side, the inside
air circulating on the other side. The air feeds the flame, then is carried
up the flue along with any exhaust gases, carbon monoxide, etc, all stuff
you don't want to breath. Meantime, the heat exchange is sort of a hot
metal box and the inside air passes over it, gets warmed, and goes
throughout the house.
 
M

MD

In response to Edwin I would state that I can understand the
theory, but it just seems like such a big opening is overkill. It
seems like there should be a more cost effective way of getting fresh
air into the basement. I would note that I previously lived in a house
with a gas furnace in a basement that was sealed and that the furnace
ran with no problems. Right now it seems as if on a cold winter day,
the furnace would be running continuously, and I would be wasting a
substantial amount of heat. Thanks to everyone for their
contributions.

MD
 
O

Old Fangled

The basement has about an 8" diameter hole (covered by a flap)
in it that a handyman said was for air circulation for the Gas Furnace
that I have in the basement. Do I really need outside air from this
hole to run the furnace?
Absolutely required. This is air that serves as combustion air for the
furnace -- drawing it from inside your house leaves you at serious risk of
furnace fires, CO/CO2 poisoning, or even explosions.
Also, if the hole does serve the furnace, is
there a way I can work around it and get the air from somewhere else?
The air has to come from the outside of your house. Think of it this way
-- all of that cold air drawn in through the pipe is immediately sent right
back outside again (up the chimney). The cold air hasn't contributed to
any cooling of your house.
It seems very wasteful to me to have an open hole in a basement during
Ohio winters, and I would like to block the hole. Thanks,
Buy a higher efficiency furnace -- they still draw combustion air from
outside, but they extract almost all of the waste heat going up the
chimney.
 
E

Edwin Pawlowski

MD said:
In response to Edwin I would state that I can understand the
theory, but it just seems like such a big opening is overkill. It
seems like there should be a more cost effective way of getting fresh
air into the basement. I would note that I previously lived in a house
with a gas furnace in a basement that was sealed and that the furnace
ran with no problems. Right now it seems as if on a cold winter day,
the furnace would be running continuously, and I would be wasting a
substantial amount of heat. Thanks to everyone for their
contributions.
You use words like "seems like" Unless you know for sure, it is speculation
on your part. More information would help. It is not a question of running
with "no problems", it is question of using outdoor air for combustion, not
the heated indoor air. That combustion air must come from someplace, even
if you don't see it. Perhaps a vent in the old house would have cut your
heating bill by 20%.

Where is the hole in relation to the furnace? What is the area of the stack
and heat exchanger intake? What is the air requirements for combustion air
in cfm? What is the Btu input of the furnace? A possible improvement may
be to duct the intake closer to the heater intake if the area around the
heater is not sealed off. .

FWIW, the boiler in a warehouse building that I operate has a motorized
damper to allow fresh air in. The opening is about 60" x 48". Yes, you
want to wear a jacket in the boiler room when it is running, but the rest of
the building is nice and warm, very efficiently.

Evidently, you don't understand the theory or you would not think you are
wasting a substantial amount of heat with the furnace running. The purpose
of the vent is to AVOID wasting the heated air, instead, using the outdoor
air for combustion. .
 
D

Decilj

Thanks for your very detailed and helpful response. I will look into
the issues you raised.

MD
 
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B

bowgus

MD said:
I have a small 1000 sq. ft. house with a basement in Southwestern
Ohio. The basement has about an 8" diameter hole (covered by a flap)
in it that a handyman said was for air circulation for the Gas Furnace
that I have in the basement. Do I really need outside air from this
hole to run the furnace?
Does your gas furnace have a chimney (or is it a high efficiency with
intake/output with PVC). If you have a chimney, the air for combustion
has to come from somewhere, hence maybe the simple flap idea. An
enclosed furnace room with outside air into that would be better.

However ... up here with a tighly sealed house and high efficiency
heating, the air in a house can get mighty stale in winter without some
sort of air exchange arrangement. So it could be that simple flap
arrangement is serving 2 purposes ... combustion air and fresh air into
the house ... and maybe that's what the handyman meant by air
circulation.
 

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