So you have the Broan 6" MD6T and you have it unfiltered, unconditioned, and ouputting under the fridge for conditioning purposes? So you are relying on the exhaust heat of the fridge to cool the incoming air? How cold did it get this past winter for you? How cold was that make up air? Detectable at all? Here we had -20 real feel in NY with the wind chill at times. It was brutally cold and cold often. I think I might have to put in a heated MUA. So update on Broan. The lady I spoke to today was completely useless. To make a long story short she had absolutely no idea how to use the Make Up Air Specifier on her site. It was quite pathetic and my impressions of Broan's customer service = suck. I spoke to Dean at Electro Industries at length about all the factors I'm thinking about. We went over two options - one using the MA-10 (10kw all in one 10" heater with damper, blower, filter, and current detector to control blower speed) and the less expensive heater unit EM-WX1025R. The broan MD6T comes with a 24volt 20VA transformer so I could then use the one signal to turn on both the Broan damper and the heater unit. Both options unit can accomodate up to 637cfm in a 50 degree temperature rise. It's a 10kW unit though and would require a 50A or 60A two pole (240V) breaker and its own dedicated lines (of course). I can take care of the electrical so no problem there but man I'm guessing my heating bill (which was astronimical last year) will be more than I can tolerate this year. Temperature Rise Needed/CFM EM-WX1025R 10000 Watts 80/395 70/452 60/527 50/632 40/790 30/1054 MA-10 $1917 + freight EM-WX1025R $800 + freight. I think that should be sufficient - it's better to have 50 degree air coming in than 0 degree air. I'm thinking that maybe I can get away with non-heated air if I can get fresh air to come up that old supply register near the range. The opening is closer than the fireplace but it might work if I put a blower in-line as well.

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.

Hi Albspam, so your in a rental now because your home is being renovated ? Make up air is required for a bunch of safety reasons. Back venting on a fire place and or water heater (and yes even on a tightly vented gas water heater it will happen). Most building inspectors are unaware of the requirement, but they are coming around. Most homes today are built to air restricted. But that's an answer for another question. Here is a very short quote... "Exhaust hood systems capable of exhausting in excess of 400 cubic feet per minute (0.19 m3/s) shall be provided with make-up air at a rate approximately equal to the exhaust air rate. Such make-up air systems shall be equipped with a means of closure and shall be automatically controlled to start and operate simultaneously with the exhaust system." There are a lot of different types of make up air systems out there. From simple... point of exhaust to more complicated. Combined with HVAC. Also, dont forget going through your HVAC will bring in heated or cooled (conditioned) air back into the kitchen and your home. If its brought back in through a vent in the wall or roof it will be the temperature outside.

We are at the very end of a big renovation and have a 1200 cfm hood. The mua will just be a damper that dumps into the return of the HVAC system. I went through all the same thought processes that you are exploring here but in the end decided to start with this (very inexpensive) set up because opinions from varying sources on what was actually needed (beyond code) were all over the place though this was the most commonly recommended so figured it would be a reasonable starting point. If I'm disatisfied, I'll explore something like the fantech system. In the interim I've just opened a window on the few occasions that I've turned the hood up pretty high. A few more data points: I'm in Chicago so get the very hot and very cold. House is 40 years old so not tight. Room is probably 700 square feet and wide open. Combustible appliances are down in the basement in their own room. There are 2 fireplaces on the first floor, one is in a closed box Let us know what you decide, I think the potential complications that Kaseki mentions that are also unique to each house cause many HVAC pro opinions to fall back to code. So many I talked to sounded like they were just guessing when I asked about heated or blown mua.