Mine looks just like an HVAC register on the ceiling. Sorry but I have no idea what the innards look like, it's just a damper that opens when the exhaust it in use so fresh air can come in from a vent on the side of the house. There is ductwork of course, and wiring between the hood and the MUA that opens the damper when the fan is turned on. The damper unit itself is not too big, the box it came in was similar size to a garbage disposal carton I'd say. Below is a picture of the MUA cover in my ceiling. (FWIW my setup is Zephyr. I think my contractor provided the cover to match the HVAC register he installed.) Hope this helps and isn't too repetitive of things you already know. Ruby

{{!gwi}}

We have not installed cabinets and MUA unit yet, but here is our plan. We have a 720 CFM hood going in over a Blue Star cooktop. MUA is not required in our area but having done research I decided I wanted it anyway. I had an HVAC engineer review our system re a return air duct issue. While he was at the house I asked him about the MUA. He noted that 720 CFM is pulling close to 2 tons of airflow out of the house/system. Definitely want MUA even if not required. Otherwise you are putting a lot of strain on your conditioned (heated or cooled) air. I purchased the Broan MD6-TU system (about $120). We will have it linked to the hood to turn on automatically.

Our HVAC guy suggested it would not be wise to connect the MUA vent to the HVAC ducting due to the burden on our slightly undersized furnace. He suggested unconditioned exterior air. We will run the MUA duct out to the side of the house through the crawlspace. Will have a vent with critter screen to the outside. The actual MUA opening in the kitchen was initially going to be in the toe kick under the cooktop cabinetry. I decided to move it over a few feet to be under the wall oven cabinetry. With unconditioned air I did not want it blowing on my feet. :) [We live in Virginia--cold winters, but nothing like when we lived in New England!]. The HVAC guy did calculations and determined that the best efficiency for our set-up was to have the duct come up under the 30" cabinet and be open to that whole space. We will install (2) 12" x 2 1/4" registers in the toe kick to maximize flow in. He thinks that with it being only 3 ft to the left of the center of the hood area that it will draw to the hood very effectively thereby increasing the efficiency of the hood in removing odors. It also should not dump much unconditioned air into the living space because the hood will draw more effectively.

Not sure if that is helpful (or even clear!). I really appreciated the HVAC guy's help--and he did it all at no charge as a favor to my awesome contractors. We are blessed... Good luck!

Thanks to you both! I'm just trying to imagine where to put it. Hadn't thought of toe-kicks, but since we're replacing a downdraft, there should be plenty of ducting from that we can repurpose.