Background –
So, I am nearly done with a 1.5 year full house renovation. Almost all work was DIY except putting in the 35′ x 16″x6″ beam and the kitchen cabs. I have a 1200 cfm (per specs) 42″ range hood over a pro style range. It uses 10″ round ducting and really moves the air.
The house is heated with a “custom” made oil fired boiler – lots of off the shelf parts – Becket burner, Honeywell controls etc. This thing was put in in 1989 when the house was built, and the thing is a tank. It is forced air draft and even has an hour meter. When I saw the thing before buying the house, I thought it was brand new. Very well maintained. I was worried it would suck down the oil, but upon having it serviced and tested, the tech was amazed at the numbers, as was I – 91% effecient and ZERO soot according to his tests. He even repeated them twice with me watching the 2nd time because he didn’t beleive it.
The house is pretty tight – 3/4″ foil wrapped isocyanate (sp) foam is the sheathing w/ vinyl siding and brick over it, R13 in walls, maybe R48 (blown fiberglass) in the attic.
The problem / question –
Anyhow, I still have not moved in and used the new kitchen, but the other day, I was rubbing off grout haze from the backsplash which kicked up a lot of dust. So, I turned on the vent hood since it was right above me – hey, neat, it is sucking up the dust I think to myself with a smile… Anyhow, I had it on setting 2 of four, so I would guess maybe 400-600 CFM. I finish the haze removal, proud of myself for sucking the dust out with my expensive range hood. Just then, as I walked toward the stairs (which go directly to the mechanical room (not finished yet), I smell fuel oil. It smelled like a deisel truck was in my kitchen.
So, it seems that I backdrafted the boiler while it was running with my vent hood. Since this was on the #2 setting, I am very worried I wont be able to use it unless I provide makeup air. Of course, the cabs and granite counters are in, so access is tough.
Here is my idea – since I plan on closing up the mechanical room from the rest of the lower level (partially below grade, not quite a basement), I had figured I would run an outside air souce to the boiler. I have an unused 4″ dryer vent opening from a previous laundry room, so I plan to connect up some 4″ duct and run it down to the boiler, and then maybe cut in a starting collar into the cover plate. This way the boiler / forced draft fan would be sucking in outside combustion air.
So, does my plan make sense? Will that keep the boiler running even with the vent on? Sould I still try to duct some make up air? Anyone have any ideas on how to do that?
Sorry for the long winded post!
-Anhy
Replies
Field Control Corp makes a combustion air fan system that can provide needed air for oil & gas fired equipment. It may be able to connect to a 4" duct; it depends on the burner btu rating and the developed length of duct . Wiring the unit in series with the burner is the safest install. Field Corp tech support may help with sizing their unit & connected duct work.
Make up air calcs should include range hoods, dryer venting, bathroom exhaust fans, attic ventilating units, window fans, etc. Some clothes dryers require combustion air as well. Again, exhaust fan manufacturers may provide make up air calculations and duct sizing / location. There is the option of hiring an hvac engineer for optimum performance and safe operation. C O detectors should be installed asap......
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