Combustion AIr for oil fired furnace


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Old 11-27-06, 08:34 AM
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Combustion AIr for oil fired furnace

Last week I called an oil tech b/c I was smelling oil fumes when my furnace was shutting down. The furnace was tuned up the week before. The tech thought the heat exhanger may have been compromised. The technician tested the draft and it was good. He did another test and said it was inconclusive. The house is 3 years old and relativley tight. He commented that maybe there was a negative pressure being created and suggested leaving a window open in the furnace/utility room while the furnace was running. Low and behold the fumes were gone. This makes sense because I just created the furnace/utility room whereas before the furnace had the whole basement for combustion air.

There is a knock out on the side of the furnace. I was going to install a vent in the side iof the house and run some ductwork to the knockout. I am guessing that this would solve my fume problem instaed of leaving a window open. When I mentioned this to a friend of mine, he suggested that instaed of running the duct to the side of the furnace that I run it to the return trunk line before the air filter and the the airflow be controlled with a weighted damper.

Which is the better option? Thanks in advance.
 
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Old 11-27-06, 03:56 PM
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What brand is the burner? There is a kit that can be used to seal the outside air to the burner.

Do you have anything brought into the home for make up air for the dryer, bath/range exhaust fan?

I would not tie into the return. Unless you have some type of control.. otherwise it's more load added to heating/cooling.
 
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Old 11-28-06, 05:09 AM
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It is a Beckett Oil Burner Model AF.

I do not have anything for makeup air. I would like to add something. Do you have a recommendation?

Thanks in advance.
 
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Old 11-28-06, 05:26 AM
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Go to this website and check out a product called the furnace boot.


http://fieldcontrols.com/cas.php


The return is under negative pressure, that would be the last place to look for combustion air.
 
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Old 11-28-06, 07:09 AM
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since you have no make up air for anything else in the home, I'd bring in a 6" pipe. drop it down near the furnace, and put two elbows in and come back up about a foot or so to make a "U" to slow down some of the cold draft coming into the home.
 
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Old 11-28-06, 09:45 AM
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Would the the Field Controls "Make-up Air System" described below work instead of ducting air into the basement??

"Field Make-up Air System consists of an Intake Air Hood which is installed through the wall to allow outside air in. The hood is connected via flexible 6" duct or standard duct pipe (not included) to our metering air device. This device effectively meters the air inflow for proper air circulation, combustion, and balance."
 
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Old 11-29-06, 04:42 AM
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That would certainly help to balance the house pressure, but consider this...

NFPA31 states that you need to have 50 cubic feet (or greater) of free air space for every 1000 btu of input for every appliance in the space. So that would mean that you add the total input btu's of the furnace, water heater, dryer regardless of what fuel they burn, divide by 1000 and multiply by 50, this would be how much free air space you need. Free air space means no doors and not filled with boxes of stuff you never un-packed that take up space. If you do not meet this requirement you must introduce combustion air into the space.

This should have been stated in the furnace instructions, read them.

The passive option would be to bring in openings, one high and one low, of 1 square inch for every 1000 btu.

The other options would be air boots or "fan in the can"
 
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Old 11-29-06, 06:07 AM
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Wouldn't supplying combustion air from the outside using the field boot affect the unit's efficiency?
 
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Old 11-29-06, 06:37 AM
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Soot affects furnace efficiency
 
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Old 11-29-06, 11:01 AM
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Wink

I just created the furnace/utility room whereas before the furnace had the whole basement for combustion air.
You say it worked ok before. You cant just close up a furnace or water heater is a small room . NO way. You need 1 sq" for every 1000Btu. So if it worked before And for the cost over all the other things. Id just grill the walls or door to this furnace room, So it can get air fron the rest of the home. You can pick up outside air later on if this dont work.
 
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Old 11-29-06, 05:16 PM
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I agree with ed that simply placeing transfer grills on the wall 1 high and 1 low will solve this problem cheaply.
 
 

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