External air feed for oil furnace - worth it?

[Mark42]

I know it is important for a house to 'breath' and not seal it up tight. So I am not going to seal off every little air leak from/to the outside. But, the furnace does pull a vacuum in the house, especially in the basement. The basement has a radon pump that pulls a vacuum under the floor so air in the basement tends to migrate out, rather than let the radon migrate in. So, now that the basement will be finished off to be living space, I want to be sure the radon pump is not foiled by the furnace. I am thinking of running a 3" rigid dryer vent from the outside to near the oil burner. Maybe even make or buy a sheet metal box that encloses the typical Beckett oil burner and connect it to the vent. It will be a short run. Either about 8 ft if it connects to the attached garage, or 15 ft if connected to outside. <br /><br />Anyone have experience with an external air feed? Do they work? Will it help maintain the pressure difference between the basement and below floor?<br /><br />Thanks,<br />Mark.

 

[chuckz]

Re: External air feed for oil furnace - worth it?

High efficiency burners use outside air for combustion. My Lenox Pulse sucks in outside air and exhausts warm air back out. The house air and the combustion air are completely separate.<br /><br />As far as affecting the radon pump, as long as the pump can pump at a higher rate than the air can get through the slab, you'll be okay.

 

[Xcusme]

Re: External air feed for oil furnace - worth it?

A few years back ,a friend of mine, had the same problem. The furnace was pulling a vacuum and the closest air source was the front door seals. Enough of a vacuum was being drawn , that buttons of frost were forming on the trim nail heads. I added a fresh air inlet pipe (PVC) to the basement furnace and the frost problem was gone. The furnace had an induced draft fan. The heating bill dropped as well. As for the supply air, some jurisdictions won't allow supply air to come from inside of a garage. I would guess it's an issue with auto exhaust. The whole system worked better, as the combustion air was now separate from the heated living space air.

 

[Mark42]

Re: External air feed for oil furnace - worth it?

Thanks guys. I must clarify that this is a hot water baseboard system. Even without a big hot air circulation fan, the oil burner still blows a lot of air into the firebox and up the chimney pulling a vacuum. I'll try adding a fresh air duct. I see that kits for hot air furnaces use a 6" pipe, I figure for just the burner a 4" should do it. <br /><br />It would be great if this caused a fuel savings! The last tune up listed effecientcy at about 82%. It was new in '92. <br /><br />Thanks again,<br /><br />Mark.

 

[BoatBuoy]

Re: External air feed for oil furnace - worth it?

Originally posted by Xcusme:<br /> As for the supply air, some jurisdictions won't allow supply air to come from inside of a garage. I would guess it's an issue with auto exhaust.

Might also be an issue of pulling volatile fumes into the fire chamber from some leaking container in the garage, i.e. gas tank. I would think auto exhaust would simply be exhausted along with fuel oil combustion products.

 

[DC698]

Re: External air feed for oil furnace - worth it?

Mark, It's now common for newer houses to have an outside air source for the heating appliances because the houses now are so air tight. I see a product called "Air in a can" (I believe thats the name) installed now in houses. Once the burner is called to turn on, it activates the fan on the system to run and draw in fresh outside air. The "can" (sheet metal box) sits close to the burner and combustion chamber. You will have to make the longer run to the outside (15ft?) instead of going out into the garage. Also, 82% efficiency isnt too bad for an oil burner. Check out your local plumbing/heating supply house for the materials. I have also seen on brand new oil burner systems the fan is installed on the side of the burner and turns on and runs for about 20 seconds before the burner ignites.

 

[Xcusme]

Re: External air feed for oil furnace - worth it?

Boat Buoy,<br /><br />That makes perfect sense (gasoline fumes etc.) Certainly, nobody wants to hear the whomping sound coming from the furnace!

 

[Hoserpoppasmurf]

Re: External air feed for oil furnace - worth it?

I haven't worked on oil fired equipment for a lot of years but have worked on 30 years worth of gas fired boilers and forced air systems. You need outside air to replace the oxygen your burner has consumed. Bring in about a 5" insulated duct and terminate it in either an inverted wye or a five gallon pail. The pail/wye will act as a cold air trap and not allow outside cold air into the house unless the burner is firing and creating a draft and slight vacuum.

 

[Mark42]

Re: External air feed for oil furnace - worth it?

Poppasmurf,<br /><br />I had heard about the 5 gallon pail air trap, but I don't see how it prevents cold air from filling up the pail and overflowing to spread out across the floor. I'm scratching my head on that one.<br /><br />The inverted Y totally excapes me too.<br /><br />You gotta give me more clues because I am.... clueless.

 

[Ben Konopacky]

Re: External air feed for oil furnace - worth it?

Mark ;hot air rises/cold drops, just think of a supermarket open top freezer,the cold air does't overflow,the warm air is holding it in place ,its heavier. more confused