makeup air vent ~5' from range?
robertgoulet
4 years ago
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kaseki
4 years agorobertgoulet
4 years agoRelated Discussions
Makeup Combusion Air Vents for Boilers and Dryers
Comments (0)Hello there. I've done the BTU input measurements of the fuel burning equipment in my basement. My 2 gas dryers, 3 boilers, and 3 water heaters total 532,000 BTU/hr. My basement, where these appliances are located, is 5,288 cubic feet in area. According to my calculations, my basement is only supplying enough air for 79,000 BTU/hr of combustion. I am at 9.9 cu. ft. per 1,000 BTU, and I need to be at 50 cu. ft. Therefore, I need 110 square inches of vent area to the outdoors for intake air, with each square inch supporting 4,000 BTU of combustion. Now, my basement has four 29x12 basement windows, each with four 7-3/4"x9-1/2" panes of glass. With a 6" round vent hood, each gives me ~28 square inches of intake air. Or, I could remove two panes of glass and screen and hood the openings instead, giving me a total of ~147 square inches of intake air, enough for my appliances. BUT, my problem is with the air... If I used 4 6" vents, none of them come with flaps (like in a dryer hood, but opening in the opposite direction) inside to stop cold air from coming in when the appliances are not in use. If I used a dryer vent sort of flapper, just turned in the opposite direction, would the negative pressure in the basement from the running appliances be enough to open the flapper? If so, where could I get just a 6" flapper? Any ideas for satisfying the combustion air while also not letting every cold breeze into my basement when they're not in use? Here's the boiler/water heater area. On the opposite wall are the dryers, with an identical window above them.:...See MoreDetermining Make-up Air for Vents
Comments (6)Our code says MUA is needed for anything over 300 cfm. Our house is 3200 sq.ft. with it's share of leaky windows and doors, so by the ASHRAE standards I should have been safe at 480 cfm. The inspector we consulted ahead of time said no, however--code is code. So my new kitchen has a 300 cfm hood with a pretty big capture volume, and a medium-powered range. If I had only checked the code as an afterthought, it would have been a very expensive afterthought indeed, requiring either the change out of range and hood once installed or the installation a heated MUA system....See MoreNeed advice for a make-up air system for vent hood
Comments (10)First, this is what the proper calculations would say about Risinger's installation. OR THIS Second, short circuiting a hood, air curtains, and generally any makeup air introduced too close to the range will produce counterproductive turbulence that will reduce the effectiveness of the hood to the point that he may as well have just put in a 400 CFM fan without makeup air. Third, the floor under the range is required to be sealed from drafts on most ranges. But, you can't usually shove ALL that air through the HVAC system either...See MoreWhere to tap into my range hood wiring to drive my makeup air damper?
Comments (54)I don't have equipment to measure the pressure differences but I have done some qualitative tests to evaluate the velocity of air that comes through a known opening (small window) for H/M/L blower settings as well as the velocity of air exiting the blower exhaust. What I found is that the pressure difference between the kitchen/dinette/family room space is greatest on the LOW blower setting and less on HIGH and MED settings even though the volume of air exiting the house from the exhaust is H/M/L as you would expect. I attribute this to the lack of MUA on the LOW setting due to the closed MUA damper. The hood flow I am perfectly satisfied with although it bothers me that the low setting is lower than designed because of the lack of MUA. I believe replacing the airflow MUA switch with a simple current sensing switch will be a good solution. We live in the PNW with a fairly mild climate with low temperatures seldom below freezing and never below 0 degree F and our furnace does not seem to have any trouble keeping up with the colder MUA inflow so far (although we have not had many cold days yet). opaone: Our MUA damper is a Broan MD10TU with a motorized damper triggered by a remote flow sensor switch. Thanks for the input on interlocking the MUA with the blower - I had thought that would be a good idea for MUA performance but not considered the static buildup aspect. The 6" MUA damper originally installed with the furnace is interlocked with the blower so I guess I better research how that works. And thanks for the kitchen compliment....See Morekaseki
4 years agorobertgoulet
4 years agoRyan Ladwig
4 years agoPinebaron
4 years ago
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