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I am wiring a new home and considering a ductless AC system for my home over central-air ducts. There will be an air handler in each bedroom and living area.

Could someone chime in and let me know what type of wiring should be in place to support this type of system? I know there will be an outside condenser too, so outside dedicate sub-panel? What about air-handler power for each room.

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It all depends on the model. Most are 240v, and the wiring connection is made through the outdoor unit.

If you're going with a multi-split setup (one condenser feeding multiple indoor heads), then you just need a single 240v connection with a disconnect near the anticipated future location of the condenser.

If you're giving each head its own condenser, you'll need many such electrical connections: one per condenser. Those'll take up a lot of room on your electrical panel; make sure it's big enough.

With this kind of cadillac equipment, make sure you're getting the absolute highest efficiency possible. The best units go up to 33 SEER and 14 HSPF. You're already going to be paying $3-4,000 per head; any upcharge to get maximum efficiency is always worth it. Don't compromise here.

Finally, be absolutely sure you select a reputable contractor who can demonstrate that they have installed hundreds of systems just like the one you're asking for. Also be sure they give you an ironclad warranty and a performance guarantee. The reason why I mention these things is that mini-split systems are pretty unfamiliar to most American contractors, most of whom only know how gas furnaces and conventional AC systems. You really need to make sure that your contractor knows what they're doing with this equipment or else you will be disappointed--guaranteed.

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  • thank you for your detailed response and advice. Also, could you tell me anything about running power from condenser to each indoor handler -- in terms of: 1. Wire gauge to indoor, (12-2 or 12-3) i don't use anything less. 2. Conduit needed on exterior wall to soffits? PVC or Metal? Thanks – true. lion Mar 24 '17 at 15:48
  • The units themselves generally include the wiring from the condenser to the indoor heads, so you don't have to rum them yourself. Conduit (metal preferred) would be needed for external cable, yes. – iLikeDirt Mar 24 '17 at 17:48
  • @iLikeDirt I agree with much of your post, but the notion of getting the maximum SEER or HSPF is a bit underdeveloped. The rating is at the maximum load, meaning it is actually better to get a slightly oversized unit (small price difference) which runs at less than maximum capacity than to get a more "efficient" unit (larger price difference) but which always runs at maximum capacity. Most inverter units also have similarly low minima, meaning a 12k unit isn't oversized for a 9k heat loss space. – Hari Ganti Mar 24 '17 at 18:04
  • @Hari Ganti I didn't say anything about sizing at all. Sizing mini-splits is a whole other subject. Oversizing a unit can be helpful, as you point out, but only if its minimum load is low enough. A bedroom in a new house will seldom have more than a 2500 BTU design load, for example. That's below the minimum modulation of many lower-quality, lower SEER/HSPF units. – iLikeDirt Mar 24 '17 at 18:24
  • @iLikeDirt I know you didn't say anything about sizing. I added the sizing bit from a recent HVAC consultation/heat loss survey because I wanted to point out the nuance between simply getting the highest HSPF/SEER and actually understanding design load, actual CoP, and resultant cost of operation. As for your example, check out these submittal sheets: acwholesalers.com/hvac/pdf/lg/lg-ductless/LS090HSV4-sb.pdf and acwholesalers.com/hvac/pdf/lg/lg-ductless/LS120HSV4-sb.pdf – Hari Ganti Mar 24 '17 at 18:28

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