29 votes

What type of cable should I run to future-proof an outlet for an air conditioner?

If you truly want to future proof, install conduit instead of cable. This will allow you to pull whatever wire you need, once you've decided what you want. 3/4" conduit should work fine, and would ...
Tester101's user avatar
  • 131k
13 votes
Accepted

120v vs 240v Mini Split Efficiency

The issue is not, generally speaking, efficiency in the sense of SEER or similar ratings. Using 240V instead of 120V allows for more efficient use of wire (12 AWG wire can handle 20A @ 120V or 20A @ ...
manassehkatz-Moving 2 Codidact's user avatar
13 votes

How do I wire a mini split that requires 208-230V with a 15A breaker, but came only with single pole wiring?

The white wire is almost certainly not neutral. L1 and L2 should be the two legs of 240V, each side of the split phase. The device needs no neutral. If you can link to the manual, I can confirm this, ...
KMJ's user avatar
  • 10.9k
12 votes

Can I use an overpowered mini split to rapidly cool a space?

Time to cool the room Heat capacity of air is negligible compared to the heat capacity of walls. You say your room is 12 ft * 20 ft * 8 ft or 3.6mx6mx2.40m which means 67m² of walls and ceilings. ...
bobflux's user avatar
  • 9,168
11 votes
Accepted

Can I use different wire gauges in quick disconnect and from panel?

That's fine There is nothing wrong with having larger wire than necessary for part of a run; most people don't upsize willy-nilly due to the cost of copper, but since you're getting a prefabricated ...
ThreePhaseEel's user avatar
8 votes
Accepted

Mini split beeping every 34 seconds

Drain pan sensor, thanks @Ecnerwal:
Evan's user avatar
  • 281
8 votes

How do I wire a mini split that requires 208-230V with a 15A breaker, but came only with single pole wiring?

In North American split-phase power, 240V Mini-splits take both hot wires. They can't use neutral. They don't make cables with red, black and no white. You are expected to buy a roll of red tape and ...
Harper - Reinstate Monica's user avatar
7 votes

How to I eliminate the smell coming from my Mitsubishi mini split units?

Posting my experience here as it may help others. This happened for the first time to me last night -- same scenario: 2-year-old Mitsubishi units, very humid day (raining on and off), low cooling load....
Chris Pacejo's user avatar
7 votes
Accepted

Couple of questions on the outside unit of a split heat and A/C installation

A refrigeration system (air conditioning, and also heat pumps) pumps refrigerant. The refrigerant is in liquid phase in the smaller tube (the "liquid line") and in gaseous phase in the ...
Greg Hill's user avatar
  • 30.3k
6 votes

What type of cable should I run to future-proof an outlet for an air conditioner?

Installing a n-3r (raintite) junction box would be fine. I would install a three wire NM with ground. You didn't mention what size your unit would be a 10/3 would handle everything up to a 5 ton. Just ...
Retired Master Electrician's user avatar
6 votes

Mini-split vs gas boiler for heating

The thing is: heat pumps move heat around rather than creating it, so they are more than 100% efficient. They collect heat from the outside air and move it inside, and depending on the available heat ...
mattdm's user avatar
  • 187
6 votes

Mini-split AC unit consuming electric power when off

It's likely a crankcase heater If the OP's mini-split was designed as a "cold climate" model (or more precisely, its heat pump counterpart in the manufacturer's product line was designed as ...
ThreePhaseEel's user avatar
6 votes

Mitsubishi mini-split not cooling very well

It would be normal for any A/C system unless tremendously oversized to try and get to set point with the inadequate insulation you have. Mini splits are very efficient but can't overcome the lack of ...
George Anderson's user avatar
6 votes

120v vs 240v Mini Split Efficiency

The efficiency has nothing to do with the voltage. Most 240V units will be larger than most 120V ones (though there is some overlap) and if you buy one that is too large or too small for your cooling ...
jay613's user avatar
  • 36.9k
6 votes

120v vs 240v Mini Split Efficiency

The loss is due to the difference in current that the wiring has to carry All else being equal*, a 240V appliance will be more efficient than a 120V appliance, because: Power loss in wiring = (current)...
LShaver's user avatar
  • 1,306
6 votes

Should I use a 15 amp or 20 amp breaker for a mini split with max current at 13.0 Amps?

To maintain code, UL et al compliance, and insurance coverage, you have to follow the manufacturer's instructions. If the unit is 240V, the 13 amps are not split between the legs. 13 amps comes in, 13 ...
Triplefault's user avatar
  • 7,280
5 votes

12/3 to disconnect box for mini split install?

Pull the neutrals out of the ground bar and join them with a wirenut Routing neutral through an A/C disconnect is rather easy once you realize that you can splice inside it just the same as you would ...
ThreePhaseEel's user avatar
5 votes
Accepted

Run mini-split heat pump heads at different temperatures

It's complete BS. If that was actually a problem, then the system wouldn't let you do that.
longneck's user avatar
  • 21.2k
5 votes
Accepted

Mitsubishi mini-split not cooling very well

It's 12K BTU/hr, and you've given it an uninsulated wall in the sun (R1, MAYBE) and a 20 degree differential, perhaps more due to sun striking the wall/roof. 600 square feet of uninsulated area would ...
Ecnerwal's user avatar
  • 210k
5 votes

What does a mni split AC do for thermostat?

As far as I know, the Mitsubishi's I have measure the temperature of the intake air at the unit. They specifically mention that they do not measure temperature at the remote. That's probably common. ...
Ecnerwal's user avatar
  • 210k
5 votes

Can I upgrade an existing breaker to add more load to a full panel?

Replace the breaker for the master bedroom A/C with the feeder breaker for your new subpanel What I'd do in this situation, since the master bedroom's window unit is getting decommissioned as part of ...
ThreePhaseEel's user avatar
5 votes

Mini split for 14x15 room addition

Sizing: TBD To get an accurate estimate of the capacity you need, you'd need more information that just the size of the room. For example, how many walls are exterior vs. interior, how much glass is ...
Chris O's user avatar
  • 6,775
5 votes
Accepted

Should I cut out this repaired kink in a copper line set? (3/8")

Your question: "If this were your house, what would you do?" I would leave it alone and use the line. A splice would be a greater interruption in flow. Get the system up and running. Then ...
RMDman's user avatar
  • 27k
5 votes
Accepted

MRCool 24k BTU breaker size, wire gauge and disconnect box

MCA of 22A means it will work on a 25A breaker. Or a 30A breaker. MOP means "not bigger than" 35A breaker (or fuse.) You don't NEED anything more than 25A as the first available size bigger ...
Ecnerwal's user avatar
  • 210k
4 votes
Accepted

Is it ok that I ran 12-3 cable for shed mini split from shed sub panel to AC disconnect instead of 12-2?

Yeah, that's fine. You can just cap the neutral. It's also fine to use larger wire than is required. You can breaker it at 15A or 20A as the heat pump's instructions direct.
Harper - Reinstate Monica's user avatar
4 votes

Can I put more than one single-zone ductless mini split on a single branch circuit?

All of the mini split system I've worked on have required dedicated circuits. Think about installing a sub panel out by the compressor locations and feeding it from your main panel. From the sub panel ...
JACK's user avatar
  • 79.8k
4 votes

Mini Split Leaking

If you want cold, you get drips. That is the reality of how thermodynamics works. Every evaporator (or on heat pumps, reversible condenser/evaporator) must have a drip pan underneath it. That is ...
Harper - Reinstate Monica's user avatar
4 votes

Wiring for mini split sysytem

Motors are weird 240.4(D) lays down a hard limit of 20A for #12 wire. However it exempts a list of exceptions. Two of them are motors, for which you follow the rules in NEC article 430 instead... ...
Harper - Reinstate Monica's user avatar
4 votes
Accepted

Can my mini split disconnect be around corner of wall

Needs to be line of sight from the unit, so anyone working on the unit can see that it's off/disabled. Not "line of sight from only one side of the unit."
Ecnerwal's user avatar
  • 210k
4 votes

Insulating outside minisplit lines

EDPM rubber foam is fairly standard for refrigeration line insulation. Having an additional covering (metal or plastic) over that for more abuse resistance is also common.
Ecnerwal's user avatar
  • 210k

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