Pre wiring for a ductless minisplit

[burninghXcsoul]

My garage build thread is here...https://www.garagejournal.com/forum/showthread.php?t=374469

I have hung the breaker box, and have run all of the wiring and boxes for the wall outlet and ceiling outlet circuits. Now I am going to be running my 220 lines. I want to pre wire for a ductless mini split that I will be installing for the upstairs area. The room upstairs is 16x40. In looking at ductless mini splits, I will probably go with a 24k btu model for heating and cooling.

Since I don't have a particular model picked out yet, my plan was to just run 10ga 220 wire to the opposite side of the building and wire it to the disconnect box on the outside while the walls are unfinished. The run would be about 55 feet or so since the breaker box is on one side of the building and the ductless mini split would go on the other side. Would this be against code to run for something in the future simply to run the wire to the disconnect box? I asked my electrician friend who is helping me out but he hasn't done residential work in a while and isn't really to familiar with NEC code. I sent an email to the code office but they really don't respond to emails and didn't seem to thrilled I was calling them up asking questions...

 

[strutaeng]

I'm not an expert, but that sounds just like I will do. My house was wired with 10 gage for a 4 ton regular split system. My electrician installed based on what I wold him on the tonnage.

I'm assuming it is all NM wire? Why don't you just run conduit and wire it later with THHN based on the actual amp load?

 

[barnee]

I just put in a three head Mitsubishi system (18k, 18k and 12k) and the circuit for the outdoor unit was 40amp.

Are you also running the refrigerant, head unit power and drain lines in the wall or are you running it outside?

I ran everything in the wall since it was new construction

 

[wyliesdiesels]

There is no NEC code prohibiting pre-wire.

Is there a particular product line you are interested in?

I would look at specs so you have a general idea of what the MCA and MOCP will be.

 

[alfredeneuman]

Don't forget a 120 Volt receptacle near the condensing unit for servicing it.
It's a requirement.

 

[matt_i]

Good stuff and a plan of mine also.

You can always run the wire and just leave it taped and labeled in the circuit panel, but none of the conductors landed on any terminals.

 

[Angelfire]

One thing to verify is whether you need a switch/disconnect for the head. Some jurisdictions have been known to require it. Something like this:
http://www.leviton.com/en/products/ms302-ds

My inspector didn't require them but I have heard of folks being told they need them elsewhere.
Cheers.

 

[pgray007]

If you pick a unit it might save some money on wire. My Daikin only needs 20A for a 24k unit. There’s also nice disconnects that also have a GFI 120V socket, so you can run 15A 120 along with your 220 and only have one hole in the wall and box on the house.


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[Norcal]

If you pick a unit it might save some money on wire. My Daikin only needs 20A for a 24k unit. There’s also nice disconnects that also have a GFI 120V socket, so you can run 15A 120 along with your 220 and only have one hole in the wall and box on the house.


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How can you have 220 & 120V?

 

[grantw]

How can you have 220 & 120V?

Interchangeable terminology.

I'd rather see 120/240 in writing myself as there is a difference... but most of us are in North America. We'll assume that you mean 240 when anything other than 208 is mentioned.

 

[wyliesdiesels]

We see this constantly on here.

But since we like to get into details, its not correct.

 

[pgray007]

How can you have 220 & 120V?

Two runs of romex

Oh, and yes that was a typo and I meant 240.


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[tailshaft56]

Two runs of romex

Oh, and yes that was a typo and I meant 240.


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Not sure of code but you can pick one side of the 240. your cable will have to come with the ground wire.

 

[wyliesdiesels]

Two runs of romex

Oh, and yes that was a typo and I meant 240.


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Where in the US would you have a PoCo that supplies both 220Y/127 and 240/120 singe phase to a residence?

220v is an actual system voltage in other countries.

 

[rburke65]

The Electrical Police strikes again!

 

[wyliesdiesels]

The Electrical Police strikes again!

Do you say that on the jobsite when apprentices are being taught?

Details are critical in this field.

The wrong information could kill someone. Especially when working on 480v and higher....

 

[pgray007]

Not sure of code but you can pick one side of the 240. your cable will have to come with the ground wire.

Agree but wanted to separate the circuits for debugging purposes and to simplify installation and inspection.


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[pgray007]

Where in the US would you have a PoCo that supplies both 220Y/127 and 240/120 singe phase to a residence?



220v is an actual system voltage in other countries.

Agree, but sometimes my typing hands get ahead of the simple logic that my brain usually does an OK job with. Part of the problem is I travel a lot and check my electronics for 220/230, so 240 feels mentally “foreign” to me as I’m not a real electrician and tend to think of 220/230 as the two phase I most worry about.

Point we’ll taken on these numbers mattering when dealing with something that can kill you, so apologies for the confusion.


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[soob]

Anyway, heh -- 20 amps will do you just fine for a 24k btu mini split. No need to run 10 gauge wire.

 

[inphx]

What about the low voltage wires from the condenser to the AC heads and the Line sets... seems you want that in the walls. Also the condensate line from the head if you want to nicely plumb it to a drain or just out the side? The line sets you will need now or later, but much easier to route before drywall.