Another Mini Split set up question

[frankd]

I'm hoping this hasn't been asked before. I did a search but couldn't find anything.
I'm finishing my basement and plan on installing a mini split in one of the rooms. I'm still debating between a DIY system or having someone else do it...but in the meantime I want to make sure I run all the necessary wiring before installing the drywall.
I only plan on using it for AC and based on what I'm reading, 12,000 btu's should be more than adequate.
My first question is, what wire size should I be running to the outside AC disconnect? I looked at a few 12k BTU units and they recommend anywhere between 14-2 to 12-2. So I was going to run 12-2 to be on the safe side. Is there any reason why I'd want to run 12-3?
Aside from the wiring for the AC disconnect, is there anything else that needs to be installed or considered before I install the drywall? i plan on installing the mini split on an exterior wall and will drill straight through the wall/foundation for the lines and drain. The exterior unit will be around the corner from where the hole is, but only about ~8 feet away.

Any feedback or suggestions would be appreciated. Thanks!

 

[ericm]

Does your code require a 120v convenience outlet near the compressor unit?

 

[dcg9381]

My first question is, what wire size should I be running to the outside AC disconnect? I looked at a few 12k BTU units and they recommend anywhere between 14-2 to 12-2. So I was going to run 12-2 to be on the safe side. Is there any reason why I'd want to run 12-3?

You need to pick the particular unit first. You're probably fine with 12 ga, but I've seen some funky things with mini-splits. I have not seen one that required a 3rd wire (neutral).

Aside from the wiring for the AC disconnect, is there anything else that needs to be installed or considered before I install the drywall?

See 2nd post.. Some places require HVAC to have a "120v convenience outlet" readily accessible near the compressor. Ref: NEC 210.63

 

[pcmeiners]

#12 2 wire is fine, if #14, you would need a 15 amp breaker, why have a smaller breaker/wire in the box when standard is #12 with a 20 amp beaker. You also need a a 4 wire control cable (#14 wire), some districts may require shielded, such as......

14/4 Stranded Copper Mini-Split Type MC Metal-Clad PVC Jacket Cable

Also Known As: 14/4 Interlocked Armor Cable, 14/4 Aluminum Interlocked Armor Cable, 14/4 AIA Cable, 14/4 MC Cable, MC Wire, 14/4 Metal Clad Copper Wire, 14/4 Type MC Wire, 14/4 Control Cable, Industrial Cable, 14/4 PVC Jacket Wire, 14/4 Copper Conductor MC Cable, 14/4 Aluminum Armor MC Cable...

nassaunationalcable.com

I would recommend a decent lightning arrestor at the outside unit or at the disconnect box, but that is later on.

 

[frankd]

Does your code require a 120v convenience outlet near the compressor unit?

...I have no idea. I'll need to look into it though. Right now I'm just going to run the wire to an AC disconnect outside before putting up the drywall. My main concern is that I'm not missing something or using the wrong wire. The space is probably around 350sq ft so even a 9k or 10k BTU unit should suffice. So I think 12-2 should be more than sufficient.

 

[frankd]

You need to pick the particular unit first. You're probably fine with 12 ga, but I've seen some funky things with mini-splits. I have not seen one that required a 3rd wire (neutral).

I'm looking at 3 different units right now. A pioneer, Mitsubishi, and Mr. Cool. Pioneer and Mitsubishi both said 14-2 in their manuals for a 12k BTU unit. Mr Cool said 12-2 but preferentially 10-2 for a 12k btu unit.
I have no idea what local places are going to charge for the install. I'm sure it won't be cheap

 

[dcg9381]

I'm looking at 3 different units right now. A pioneer, Mitsubishi, and Mr. Cool. Pioneer and Mitsubishi both said 14-2 in their manuals for a 12k BTU unit. Mr Cool said 12-2 but preferentially 10-2 for a 12k btu unit.
I have no idea what local places are going to charge for the install. I'm sure it won't be cheap

You're probably fine with 12 gauge, but I'd go by the manual. Right around the 24k size, I've seen some that want 10ga wire (even though my 24ks will run on 14 awg with a 15A breaker). That's why I mention it.

Buddy just got a quote for his garage, main panel is outside near the potential compressor. They have to go throuh faux masonry, but they quoted $6500 for the install. I'm in the wrong line of work!

 

[frankd]

You're probably fine with 12 gauge, but I'd go by the manual. Right around the 24k size, I've seen some that want 10ga wire (even though my 24ks will run on 14 awg with a 15A breaker). That's why I mention it.

Buddy just got a quote for his garage, main panel is outside near the potential compressor. They have to go throuh faux masonry, but they quoted $6500 for the install. I'm in the wrong line of work!

$6,500 for the install?! Looks like I'm doing the DIY Mr. Cool. lol
It really doesn't seem too hard. The most annoying part is probably drilling through the foundation.

 

[dcg9381]

$6,500 for the install?! Looks like I'm doing the DIY Mr. Cool. lol

I think that's in "local dollars" from on of the big commercial HVAC spaces. I'd expect about 1/2 of that.

The most annoying part is probably drilling through the foundation.

Hope you're not on post-tension.