ERV instllation question
I will be installing a Broan B130E65RS in a three bedroom 1400sf house. Each bathroom will have its own exhaust fan and the kitchen will have a 190cfm exhaust vent to the outside. The design calls for 100cfm and just an exhaust in the hall upstairs and only a main supply in the open space downstairs. The takeoffs on the ERV are 5″. Broan calls for flex duct for the runs to the exterior to a tandem outlet. I was planning on installing 5″ flex duct for these runs.
I will install a short section of flex to 5″ round that transitions to 6″ oval up to a 6″ X 12″ grill at the top of the wall in the upstairs hallway and flex to a 5″ round directly to a ceiling register in front of the ductless mini-split in the main room downstairs.
Just looking for any feedback on this plan.
Thank, Ralph
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Ralph, what climate zone are you in? How many occupants and pets? Is there a basement?
Based on quite a bit of C02 level testing on my own setup (one supply in main living on main floor, 3 bedrooms on second floor), I'd highly recommend doing say 10-15 CFM supply (per person) to each bedroom on the 2nd floor if you are able and consider doing 50-60 CFM supply, or 100% exhaust, in your main living area on the 1st floor. Bedrooms are where Co2 PPM levels peak the most during 24 hours. If your kitchen is in that main 1st floor living area, an exhaust(s) on that floor will help with cooking odours etc.
The longer runs to the 2nd floor and night time (cooler temp) preferences in bedrooms may obviate the need to post condition the ERV air. You may need to think about post conditioning if using just one supply in the main living area.
Dennis thanks for the reply. The house is a Habitat for Humanity house in zone 5. I have just volunteered to help with the installation of the ERV. I did recommend running supplies to each bedroom but the Hers rater who is in charge of the design said that it was not necessary. My main concern was whether or not I should upsize the ductwork.
Hi,
I have used the Broan tandem unit with a Panasonic 100cfm ERV - it adds a decent amount of static pressure so my best advice is to make the rest of the system as free flowing as possible, including making the resort of the ducts as large as reasonable.
Also, it has oval connections which are extremely annoying to use. Taping the connection after zip tie is difficult and there is not a lot of room. Mastic would work better, but given the unit is styrofoam, that would be a one time shot.
My best advice - ditch the dual hood. I thought it would be easier/better to have one hole, but it’s literally a compromise in every other way.
In the end, I switched to a Cerv2 with dedicated supply to all three bedrooms and a return to each bathroom(2). Ranch style 1320sqft 3/2. Running ~170 cfm right now and it’s silent, bath fan hasn’t run since, and co2 stays low. It’s glorious.
Thanks for the info on the tandem unit. I had some concerns using this setup. Adding a second penetration thru the exterior is not much additional work. From the picture it looked like the connections were ovel.
Those duct sizes sound reasonable for 100 CFM, but you should really post up a sketch with lengths/elbows if you want an experienced HVAC person to chime on on flow. Dumping in front of the mini split should address the supply temperature issues which in zone 5 won't be great.
Thanks for the reply. The duct runs are 15' for one and 25' for the other both with two 90-degree elbows.