How far will a ductless minisplit throw heat/cool?
Clay Whitenack| Posted inGreen Products and Materialson
Assuming an open area with a good line of site, what can you expect a ductless mini split to throw heat/cool. For example, if you have an open, but large floorplan, could you put a mini split on one outside wall and have it throw heat/cool to the other wall which is, say, 40′ away? What about 50′?
Fujitsu has a Design and Technical manual (https://portal.fujitsugeneral.com/files/catalog/files/DTR_AS115E_01–ASU9-15RLS3_H1.pdf) for their wall units that has a lot of great stuff in it, including this very detail, but the chart only goes to 29 ft. There seems to still be some velocity left past 29 ft, but I don’t know if it stops at 35′, 40′, etc.
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Clay,
If a building has an excellent thermal envelope -- one with a very low rate of air leakage, with above-code levels of insulation, and with high-performance windows -- temperatures will be fairly uniform, even in large rooms, as long as the room is not interrupted by partitions and closed doors.
We have a living/dining/kitchen room of about 800 square feet, with ceilings from 8-14 feet. A Fujitsu 12RLS 3 has no trouble warming or cooling the whole room, with fan on low. We're in Maine, zone 6. But, as Martin says, the key is a tight, well-insulated house. You want to be comfortable, not feel the breeze.
Thanks folks. If a zone needs, say 10k BTUs, but it has a room off of it (included in the 10k BTU calculations) that may be a little harder to get the heat/cool because it is not in a direct line of sight (but still through open doorways), would a 12k head get it there OK or would it be better to step up to a 15k to help disperse the air? ETA: I realize a larger head is not quite as efficient, but it looks like the minimum modulations are the same, so upsizing wouldn't cause problems from that standpoint.
Also, do ceiling fans hurt a mini split distribution? If you put a head on a wall in a room and aim it at the large opening for the rest of the house, but have a ceiling fan in the same room between that head and the doorway, would the fan short-circuit the mini split range? In some ways I could think a ceiling fan would help disperse the air (but I know fans are mostly for wind chill), but in other ways I could see it blowing the heat/cool back towards the head before it could extend through the room to the rest of the house.
Clay,
My advice would be to go with a right-sized minisplit, not an oversized minisplit. If the door to the adjacent room usually stays open, and you have a high-quality thermal envelope, I wouldn't worry.
If you plan on using the minisplit for cooling, then I don't think you need a ceiling fan. If I were you, I would skip the ceiling fan.
Clay: I don't think you need to oversize either. With a tight envelope, distribution isn't an issue. You'll get very even temperatures throughout the space. The better the envelope, the more consistent the temperature will be.
I'd skip the fan too.
One issue some people have with minisplits is keeping the temperature at the remote set point. Putting the inside unit too close to a ceiling seems to often cause the temperature sensor in the unit to assume the room air is warmer than it is. The solution is to install the unit lower than just a few inches from the ceiling, even though the installation instructions may say 4" is OK.
我有一个相当典型的分裂。我们有kitchen and dining area on the back of the house. The master bedroom is on the back half of the house, with it's door at the end of the hallway. There's an ensuit bathroom off the master, to get to this the heat has to turn 180 degs. There's also a main bathroom, between the dining room and the ensuit bathroom, in the back half of the house. The front half has the living room, entry way, and two kids rooms.
Our house has fairly standard insulation, 2x6 walls with batts, OSB and siding, and ~R60 in the roof. We have pretty low ach50 of 1.62 though.
Last January we had a mini split installed and used it for heat in the winter. There was about a 2-3 degree temperature differential from the ensuit bathroom to living room. I was very satisfied with that.
Thanks for the replies.
Stephen, I'll have 9' ceilings, so I shouldn't have any problem dropping the unit 4-6" and still have enough clearance below.
Calum, thanks, that's encouraging. Where did you place the mini split in relation to the rest of the house?
It's on the outside wall that's shared with the kitchen and dining room, pointing directly at the archway going to the living room and front door. I have the louvers turned to push the heat down the hallway toward the bedrooms.