Mini-split A/C install

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petersonra

petersonra

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Northern illinois
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engineer
A couple years ago I talked to an HVAC guy about putting a mini-split A/C in my bedroom. It is the main room I use so I figured it would be cheaper to cool one room than the whole house.

The guy suggested several ways to run the power. One was EMT on the outside of the house either along the bottom of the vinyl siding or behind it. The other was to hide UF behind the vinyl siding. I am not real thrilled with either solution but after looking closely at the code it would not appear to me that either approach is in violation of the code.

he also suggested if I could find a 20 Amp 120 VAC circuit that I didn't mind losing that I could use that if it was more convenient. Somehow this does not seem right to me, but as best I can tell all my outlets are on 15 A circuits so is kind of a moot point.
 
Running UF under the vinyl sounds like a code violation to me. I don't think the cable would be sufficiently protected from say a shovel accidently cutting it. Vinyl siding is not a valid conduit type.

I install many mini-split circuits each year. Here's how I do them:

Run a new circuit out of the panel, up into the attic, and down from the eave next to the mini-split. Use UF and sleeve the UF in PVC from the eave to the disco.

If the panel is close to the mini-split, you can run EMT on the outside of the house to the disco. Just make a penetration below the panel and use an LB from the panel bottom to go from inside to outside.
 
I just wired one recently. The outside unit was placed near an existing whole-house generator, so I ran 1/2" PVC (not EMT) and added my 1-hole straps to the existing screws holding the genny's PVC run.

I would opt for PVC instead of EMT in almost any outdoor installation with smaller circuits.
 
I don't know why something behind the siding is even a consideration.

On a single head split unit, you power the outside unit, then the inside unit daisy-chains. Basically, it gets wired like 2 smoke detectors. You power the first unit with 2-wire, then run 3-wire to the next for power + single control wire.

Whatever route the lineset takes from the outside unit to the head unit, you run the interconnect cable alongside it. Are you planning to run freon lines behind the vinyl siding? I would think not
 
It all depends on the construction of the house. Florida=no basement, right? We don't know where your panel is either, so basically it's up, over through the attic and down or around the outside.

The condensing unit will be located under or near the indoor unit with the line sets and interconnecting cable up the outside of the house covered by a "U" shaped cover (I'm sure the HVAC guys have a name for it). If you opt to go through the attic you could extend the U cover up a little higher to where the attic is, then just use UF for the entire run.

If you have to run it around the outside, your only real choice is PVC. RGS would certainly eliminate the sagging problem though.

-Hal
 
James L said:
I don't know why something behind the siding is even a consideration.

On a single head split unit, you power the outside unit, then the inside unit daisy-chains. Basically, it gets wired like 2 smoke detectors. You power the first unit with 2-wire, then run 3-wire to the next for power + single control wire.

Whatever route the lineset takes from the outside unit to the head unit, you run the interconnect cable alongside it. Are you planning to run freon lines behind the vinyl siding? I would think not
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The freon lines run through the hole in the wall so no reason to run them under the siding.
 
petersonra said:
he also suggested if I could find a 20 Amp 120 VAC circuit that I didn't mind losing that I could use that if it was more convenient. Somehow this does not seem right to me, but as best I can tell all my outlets are on 15 A circuits so is kind of a moot point.
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A lot of older homes did have a few 120V 20 amp circuits run for window units years ago. Sometimes you get lucky and sometimes you don't.
 
James L said:
Wherever you run your Freon lines, run your electrical alongside it
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The line sets usually aren't routed anywhere that would help with the branch circuit wiring, unless the situation was through the attic as I pointed out previously. Certainly you would run the interconnect cable between the indoor and outdoor unit with them though.


petersonra said:
I think on these kind of units the freon does not have to go outside at all. It goes from the part that is outside to the part that is inside through a hole in the wall.
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Umm yeah, the hole in the wall is through the side of the house (behind the indoor unit) with the condensing unit on the ground below it. Unless of course the indoor unit is on an inside partition, then it's possible (but a real PITA) to fish the insulated line sets but they still have to get to the outside to connect with the outdoor unit somehow.

Also, let's not forget about the condensate drain line. When the indoor unit is on an outside wall, the 1/2" PVC drain line follows the line sets and dumps out on the ground. With installations where the condensate can't drain by gravity, there are condensate pumps, but that shouldn't be your situation.

-Hal
 
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While it is possible to run the electrical inside the line-set cover, it's usually not practical. The head unit will be on an exterior wall of the bedroom. The line-set will penetrate the wall behind the head unit and then down to the condenser on the opposite side of the wall. The line-set will likely will not go into the attic. The electric needs to come from the attic or be run along the wall. The line-set and the electric do not intersect.
 
I think the guy wanted to avoid attic work by running power out the wall from the panelboard behind my refrigerator. It would be more or less a straight shot to run it along the bottom of the siding on the outside to the vicinity of the unit.
 
Coppersmith said:
While it is possible to run the electrical inside the line-set cover, it's usually not practical. The head unit will be on an exterior wall of the bedroom. The line-set will penetrate the wall behind the head unit and then down to the condenser on the opposite side of the wall. The line-set will likely will not go into the attic. The electric needs to come from the attic or be run along the wall. The line-set and the electric do not intersect.
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I just installed a Mr. Cool unit Saturday, and I've installed at least a dozen others of various brands. Every single time, the lineset and interconnect cable took the exact same route. There's a space in the back of the head unit to run either the lineset or the electrical (or both) to either end of the unit and out the wall. Drain line takes same route
 
petersonra said:
I think the guy wanted to avoid attic work by running power out the wall from the panelboard behind my refrigerator. It would be more or less a straight shot to run it along the bottom of the siding on the outside to the vicinity of the unit.
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That's what I'd do. Straight down and straight over - on the surface, in pipe. Won't look any worse that meter riser, cable tv, etc
 
James L said:
I just installed a Mr. Cool unit Saturday, and I've installed at least a dozen others of various brands. Every single time, the lineset and interconnect cable took the exact same route. There's a space in the back of the head unit to run either the lineset or the electrical (or both) to either end of the unit and out the wall. Drain line takes same route
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Not talking about the interconnect cable. Of course that follows the line-set. I was referring to the power cable.
 
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