Make-up air systems
Scott MacDonald
6 years ago
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catinthehat
6 years agoScott MacDonald
6 years agoRelated Discussions
New construction: venting and make-up air for 48'' range
Comments (4)Wow! A rare case where the aesthetics part of the performance-aesthetics-economy: pick-any-two limitation is not a factor in hood selection. But first, given a sealed household, I would strongly recommend obtaining a furnace kit to use outside air. This will avoid the possibility of the MUA system not working perfectly and the hood causing negative house pressure and hence backdrafting of the combustion appliance. I know that such devices exist for Beckett burners, and would guess that there are adapters for other burners. As the OP correctly notes, a 200 cfm ERV is not going to cope with a 1200 cfm vent hood. (Actually, what would happen with a sealed house is that at full power, the hood would pull the cfm the ERV would let through into the now minus a couple of inches w.c. house pressure.) So MUA is essential, and in the mid-Atlantic region would be pretty uncomfortable in winter if unheated. Depending on one's tolerance for heat and humidity, cooling in summer might be optional or not. We are starting to get into the realm where performance-economy, pick any two is applicable. MUA can be roughly characterized as passive or active. By passive is meant no fan in the circuit. Active uses a booster fan to keep the house pressure stable. No-fan only works for simple ducting with a vent hood air flow controlled damper. (A recent post here provided some sources for these.) If a filter is used at 1200 cfm (or whatever flow actually could be pulled with all the doors and windows open, then the house pressure will drop. One can see on websites selling filter packs that the pressure drop at such flow rates is too large for combustion appliance safety, which require negative pressures not be greater than 0.03 to 0.06 inches depending on appliance type. Active is needed to overcome the filter restriction. It may be needed to overcome heating heat exchanger restriction and/or air conditioning heat exchanger (expander) restriction. The difficulty with active is balancing the MUA air flow rate against the variable hood flow rate such that the house pressure is near zero. This usually requires a control system of some sort, and can be a "project." What to do? What to do? Only one free-of-processing-controllers active MUA has occurred to me. In the simplest embodiment, the hood control is connected to two parallel wired identical fans, one in the hood exhaust path and one in the MUA path. Then the two will (try to) operate at nearly the same flow rate at every control setting, and one only needs to adjust the MUA duct restriction until it matches that of the hood path. More exactly, adjust the MUA path so that house pressure falls very little as the hood is turned on. Note that this doesn't account for bathroom fans, fireplaces, or other exhaust flows not due to the hood. In such cases, PID control of the MUA fan would be needed. In my case, due to a 1500 cfm hood, 1000 cfm over-oven vent, fireplace, and three bathroom fan household, I am building an active MUA that will use an axial blower in the 2000 cfm regime. It has to overcome the pressure loss of its intake vent, its filter, and its heat exchanger (which is hot water pumped from my oil burner). Control is via a Fuji PID controller operating from a BAPF differential pressure sensor. The motor power control is not yet selected, and a lot of sheet metal action is still needed, along with further attic revisions that I seem to have trouble getting to at the needed rate. I recommend the OP and/or his HVAC person read the "Kitchen Ventilation Systems Application & Design Guide" that may be found at Greenheck's web site. It periodically moves around, URL-wise, so a Google search by name may be fastest. Greenheck or one of its competitors may be able to provide what you need for considerably less agony than a do-it-yourself HVAC project would. kas...See MorePlease advise - Make-up Air system
Comments (2)The Broan makeup air damper for kitchen ventilation was the first residential application on the market. I think they deserve some credit for offering this design while others were silent. I've read the easiest passive make up air approach is a run of tubing in the basement through the crawl space to the outside, with an appropriate critter cage attached. I've had to read the below Broan MUA spec sheet a couple of times or more. Newer models may be available. Looks like you best come up with a installation guide for the Ventahood you choose. It will address a lot of the questions you ask. So you're going to run the ventilation ducts up to your attic and then out exteriorly to a cap? Your HVAC contractor should definitely be in on that. Good luck. Kitchen range ventilation is tough on the mind and budget for many of us. Here is a link that might be useful: Broan MUA damper This post was edited by SparklingWater on Mon, Feb 18, 13 at 21:47...See MoreNeed help figuring out a make-up air system to install
Comments (4)Your builder is supposed to know. Contract the hood to a COMMERCIAL installer and they will make sure system is right. My experience with commercial kitchens has been that make up air is provided intergal to vent-a-hood. There is no reason for tempering air in the comfort system when air can be drawn in ajacent to range. Hopefully that answer's your question,here's mine. Are you acting as your own GC? If you are and haven't started yet you should reconsider because there will be far rougher roads ahead concurning the build. If you have a GC and haven't started,hire a new GC....See MoreChoosing a Make Up Air system for a 1959 house
Comments (0)I have a 1959 house in Gainesville, Florida. I am buying a 30" induction cooktop on an island. I am looking either for a hood or a downdraft system, maybe Captura Best, but I think I am gonna go the healthier way (a hood). I have these questions: 1) I think I want to have a Make Up AIR system (MUAs) even if I choose a 400 CFU unit. Although in Florida I can probably go up to 800 CFU, cause I think I have no "gravity vent appliances" (no fireplace and no gas, I will double check with my HVAC if the furnace in the heat pump heating/cooling system is an issue) I still think its better to have the MUAs and not to draw air from gaps and crawl space (where I actually have a Radon vent to vent it outside). Besides the obvious better performance of the hood compared to downdraft to remove fumes, is there a difference in how I should design the MUA system given the CFUs (e.g., is the MUAs design and cost the same for a 400 CFU downdraft or a 400 CFU hood)? 2) I have no ERV system. Can I buy an ERV system that has an embedded MUAs, or it does not make much sense (Spurpura on this post says that she has one, she says "high-end ERV systems (including a mix of other parts and computer and analog controls) can control the mix of indoor and outdoor air on the fly. Under sealed home conditions, this would result in positive, negative, or neutral pressurization for the home. When the vent hood is taken into consideration (providing a source of negative pressurization for the home), the ERV system can be set to mix more outdoor with indoor air to achieve positive/negative/neutral pressurization (as desired)."). 3) assuming that a ERV with embedded MUA is a bad idea since my house might not be sealed (how to test?), where should the MUAs air enter my open space kitchen/family room area? 4) Is a silencer needed for the MUA? 5) What is the best way to activate the MUA once I turn on the hood?...See Morecatinthehat
6 years agokaseki
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6 years agoScott MacDonald
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6 years agoScott MacDonald
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