Oil Furnace Intake

[phuzman]

Hi,
I'm a glassblower and have a small studio in my basement where I blow glass at a torch. I have a 1200 cfm fan in one basement window and have another open window 12 feet across from the fan for fresh air intake. My oil furnace is also in the room about 15 feet away. I've been told I need to install an additional fresh air intake for my furnace (there is not one already present). There is very limited space to fit a large duct since the walls are concrete with only a small area of wood at the ceiling to drill through. Would a 3 or 4 inch pvc pipe running from the burner to the outside be adequate air intake for the furnace? I've called several HVAC pros and keep getting different answers. I had a different setup in my old house and didn't have to worry about this before.

[bkcalhoun]

Let me qualify my response with this: I am not an oil man. I do natural gas and propane.

Check this out.

http://www.fieldcontrols.com/cas.php

I'm sure someone more in the know will step in here.

[firecontrol]

Only comment I'd like to make is:
I sure hope you have good carbon monoxide detectors not only in this room but other recommended areas of your home.

[beenthere]

You might need an air intake for the furnace.

Can't see the room or door from here.

Did you have this studio built.

[snupytcb]

Only comment I'd like to make is:
I sure hope you have good carbon monoxide detectors not only in this room but other recommended areas of your home.

honestly, not as many people die from carbon-monoxide from an oil fired unit because they usually get out of the house in time due to exesive smell and soot. i do believe you should have 1 sq. inch of free space for every 2000 btu.

[phuzman]

I have plenty of detectors in the house. Would it help if I posted a drawing of the room? It's about a 25 x 15 foot room with the work area on one side and the furnace at the other end of the 25 foot length. The intake window for the bench exhaust is almost directly across from the window that the exhaust fan is installed. I've been working like this for a month w/o any incidents but I know that doesn't mean I'm being safe. I want to be sure so when it gets cold and the furnace is running more I don't have any problems.

[phuzman]

Anyone know if I need an intake? I re-measured and can probably fit a 4" vent but that's probably as big as I can fit.

[heaterman]

Too many variables and not enough info. A problem will result if you create a negative pressure situation in the area where the furnace is located. The draft for the oil burner will be impacted altering the air fuel ratio causing sooting or worse. A reverse draft at the barometric draft control could result in combustion by-products being drawn back into the furnace room area (heat coming from the draft control would be one indicator). You really need a mechanical contractor to check out your situation and make the proper recommendations. As far as CO problems, not nearly as likely as with natural gas. Your insurance company, on the other hand won't be too pleased if you soot up the interior of you home with a DIY project that goes astray. :rolleyes:

[phuzman]

I appreciate the response. I have been working for weeks with the exhaust set up this way. If there is no soot or backdrafting does that mean that it won't? I've had several oil companies send out guys and have had all of them tell me something different ranging from "You're fine" to "You need a 6 inch intake".

[heaterman]

It does not mean that you won't experience a problem some where down the road. There are numerous factors at play the most obvious one being weather. We are in a transition period coming up on winter when furnace run times are increasing, ventilation in homes and businesses is reducing do to closed windows and doors and exterior conditions impacting on the draft characteristics of your chimney system. Adding dedicated make-up air to the burner compartment of your oil furnace is not a bad idea and it's always better to error on the side of caution. There are kits on the market the first one that comes to mind is by Field Controls that are designed for this purpose. They won't be available as a DIY, have a reputible oil service contractor take care of your needs. A little spent now will save you a bubdle later.

[Leo]

If you had a dusty environment I would recommend a fresh air intake direct to the burner. But!!! In your case you have the exhaust fan which changes everything. You will not only be starving the fresh air intake but also pulling the exhaust back in through the draft regulator. My recommendation, enclose the furnace leaving enough room for it to be serviced. Then add a Fan in a Can which can be seen on the Fields web site already posted. This will bring in air when the burner is running for both the burner intake and the draft regulator. We used to do this at a company I used to work for. We had an animal hospital that added an exhaust fan, it pulled CO back into the building and killed some birds plus they always had odor complaints. Enclosing the furnace may sound like a lot but your are doing something out of the ordinary in your basement. There are necessary minimum clearances to enclose the furnace and the Fan in a Can has to be properly wired into the burner circuit. This is a job best left to a pro.

Leo

[johnsp]

Has a 4" intake on the air box.

[skippedover]

Depending on the oil burner that's installed, there are various methods of alleviating any possible problem of combustion air starvation. If your heating unit uses a Beckett AF or AFG oil burner, there is a kit that can be installed to provide combustion air direct from outdoors. If you do not have a Beckett burner, then I'd recommend enclosing the furnace in a separate room and providing ventilation at the top and bottom of the room, connected directly to the outdoor. If the unit is adjacent to an outdoor wall, simple grilles high and low would work. If the unit is not adjacent to an outdoor wall, then you'd need to ducts installed for ventialtion.

IMO, a 1200 CFM exhaust blower is big. That's equivalent to the entire airflow from a 3-ton AC unit. If you have adequate make-up air coming into the area to fully satisfy the exhaust blower, then the oil burner doesn't have much of an issue, as the interior air pressure is neutral. But if the blower starves for air, even a little bit, it will suck the combustion air from the burner and probabaly pull exhaust by-products into the living space, at the very least after the burner has shut off from a heating cycle. The potential for CO poisoning is nearly zero as you've already got a huge exhaust fan pulling in lots of fresh air. But the potential to damage the burner and it's various components and/or cause soot damage to the interior of the space is significant.

[Leo]

I just remembered we had a unit in the work area of an auto dealership melting burner components. After investigating we found they had installed a large exhaust fan activated by a CO sensor. It was pulling the exhaust heat backward into the burner. The solution, an electrician installed a relay. When the fan ran the burner wasn't allowed to run. This may be the cheapest alternative.

Leo