View Full Version : Boiler Combustion Air venting question

11-17-2004, 10:38 AM
I am doing electrical and heating planning for finishing my basement.
The basement is approx 1300 sqft and it contains our 176,000 BTU/hr oil boiler/furnace.
After computing the heat losses I have decided I would prefer to only heat the "Family Room" portion. But... the shop area is where the boiler is and so I must somehow provide combustion air. Can I do this with an outside air vent? The wall next to the boiler contains a 10" wide cutout in the foundation wall that starts about 1/2 way up and extends up to the joists. It seems like that may be what it is for?

What would be required such that I would not need to vent to the "Family Room" (the shop+mud room is well below the confined space limit)?

Is one vent sufficient or would I need two? What size?

Can this be a free air vent or does it require a fan? What decides that?

Where would the vent(s) empty out / attach? Does it need to attach directly to the combustion chamber?

What keeps the vent(s) from turning my shop into a freezer? I don't mind if it isn't heated but I do want it to stay well above freezing.

Anything else / other comments would be greatly appreciated.
We moved to the North East from Houston Texas so basements (called indoor swimming pools in Houston) and cold weather (30 is cold for Houston) are still a learning experience.


11-17-2004, 05:13 PM
IF you can find the installation manual on-line (assuming you haven't bought the furnace/boiler?) yet, read it. It should discuss this. Most I've looked at do. Usually, you need an opening near the floor level and another one higher up. A boiler that big (must be a big house or poorly insulated?) needs a lot of air. Can you wall the area with the furnace off? That would make it easier to keep the workshop warmer. Many of the new boiler/furnaces use direct venting - that means that they use a pipe to bring in outside air for combustion and then push out the exhaust. Many of these use plastic pipe because they can extract most of the heat from combustion prior to blowing it out of the flue. Does the system you are planning support direct venting? If so, your problem is solved.

11-17-2004, 11:42 PM
As pointed out above, combustion air is a very important issue. If not direct vented, you need 1 square inch hi and low for each 1000 BTU. So you would need 2 openings about 10" X 17". This is really not a do-it-yourself project. You need more technical advice from an on-scene professional. Gas, flames, carbon monoxide.....this is serious stuff.

11-21-2004, 11:54 AM
Thanks guys,
I called the boiler manufacturer (New Yorker) and identitied that I have a Beckett AFG Burner http://www.beckettcorp.com/product/productdetail.asp?detailid=11 and there is a fresh air kit available for that burner. He recommended using a fresh air kit and using a professional since the Burner would require readjustment for the new air supply that requires equipment I won't have.

Now that I know there is a solution for proceeding with outside venting I plan on finishing the rest of the stuff I need to do for the rough-in inspection (walls, electrical, and heating) and then check with the inspector about the outside vent when he comes out for that. In the mean time I need to price out my options of what I can do myself and what a professional would charge. I also have a guy I work with that has taken "do-it-yourself" to the next level who put a fresh air kit on his furnace. Note: The guy I mentioned is a fellow engineer and not just built his own house but also has even gone as far as building his own dam and lake; all approved by the state.


11-21-2004, 12:58 PM
If you are handy, can follow instructions, are willing to ask questions about things you don't understand, then this could be done by yourself. It will go faster if you hire a professional. Getting or renting the tools to check the pressure drop, and adjusting the flame are things that are easier for a pro who does it all of the time. Note, some of those guys don't know what they are doing, either - bad apples in every barrel, but most are good. You could do some of the work, cut the holes, place the vent in the wall, and leave the final installation and adjustments to the pro. Check with them first, though, some won't take a job unless they do the whole thing.

10-08-2005, 11:23 AM
Things are progressing on the basement project and my wife is starting to ask about stuff. One thing she has noted several times is the "oil smell" that we get in the basement. She says she notices it the most when the "whole-house fan" is on and the furnace is running.

Will putting a outside air kit on the furnace help reduce this? If so, I may want to move adding it up on the schedule. Also, are there any other things I should do? When the project is finished, the furnace will be in my 16'x14' wood shop. There isn't a window in that room and I hadn't planned for any special ventilation for that room and I don't want to get entoxicated. I do suspect I need to put a CO alarm in that room.

P.S. The vent kit I plan on using is a Field Controls CAS-2B (http://www.fieldcontrols.com/instructionmanuals/46273500.zip) and will cost $96.