Spot ERV feeding fresh air to minisplit evaporator head
First off, happy new year and my deepest thanks for all the help from the members of this community! We finished construction of our small, energy-efficient house this November after 14 months of extremely hard work, and couldn’t be happier with it’s comfort and performance so far. Much of that is thanks to the resources provided here at GBA (and a special shout out to Martin feels appropriate).
I wanted to proposed another somewhat unconventional design consideration that I was considering, but am in now way attached to.
I purchased a Panasonic FV-04E1 Spot ERV to compliment our Fujitsu 15RLS3Y mini split (which has been doing great by the way with many nights this past week in the low negatives and single digits).
I was wondering if anyone here has considered placing ERV/HRV fresh air vents directly above mini-split heads, the idea being that the mini split is directly warming/cooling fresh outdoor air and further distributing it throughout the room.
In this case, because our house is only 720sq ft with no in wall duct work and a single, centrally located mini-split head, the main purpose would be the added fan power of the mini split head helping the fresh air better reach the whole house.
I remember reading somewhere about greater temperature differential (delta T) at the mini split head also improving operating efficiency. I was wondering if anyone can chime in about this specifically? It is of course an important consideration, given that if the inverse were true, this design would be a very poor decision. It does make intuitive sense that cooler air moving over a heated evap coil would help extract the maximum heat, improving efficiency. This is again relevant because this ERV is only rated at 66% efficiency for heating.
I am curious to hear what you guys think, and again, thank you so very much for all the help over the past year and change!
Cheers,
Zane
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Replies
That certainly would work. I'm not sure if it is worth the trouble though, these pretty low flow rate, if you can get the air into a larger space, you might not notice the colder air just from natural mixing.
If I remember correctly, there is a kit for these units to duct the fresh air supply. You can leave the main unit in the bathroom and run this to the inlet of your mini-split.
It will improve efficiency, but it will be a pretty small amount 0-3% is a guess. I would have to check my numbers, but I worked out what the gain would be by dumping a non ERV fresh air supply into a slimduct unit. I recall it was something like a 5% reduction in energy use in the best conditions. I’ll have to dig up that spreadsheet again.
For comfort purposes it might not be a bad location if there isn’t another somewhat out of the way spot.
Zane,
Really glad your house turned out well.
Cheers!
Thank you guys so much! I was hoping for some information right along those lines. As you can see in the first photo, the proposed spot for the ERV is alread just adjacent to the ductless head, so it’s a minor inconvenience. The main advantage is the fresh air blowing out into the main room rather than into the loft.
Thank you Malcom for the kind words. I have a newfound respect for contractors around the world. What an endeavor to build even a little house! We are so happy with how it turned out though. It was a commitment but we went for traditional three coat interior plaster and are so thankful we did.
Since you have the space there, I would be temped to go with an Intellibalance unit. It is a lot more expensive, but way more efficient. I installed a 75% efficient unit for my home, couple of years down the road, regret not getting something better.
It also has enough flow rate that you can install a boost switch and use it to clear the house when cooking. You can also put a small drop to feed fresh air directly into the bedroom.
Installing this would not be much more work than the spot ERV.
P.S. That is fantastic view out of the dining room!