Garage electrical for Mini-split

[markfraser33]

Hello!
I'm building a small office room in the corner of my unfinished detached garage and plan to install a mini-split.
The one I like is 120v with an MOP of 20 amps and the circuit feeding this garage is only 20 amps.
Plus the overhead wire feeding the garage looks like only 2 of the 3 wires are connected at the house, I'm assuming its the ground that not connected.

I know i'll need to increase the 20 amp circuit to the garage and redo the suspended (or buried cable) to the garage to match the breaker amps - hoping to do that (or hire someone) after the garage work.

-i'm planning to install a subpanel in the garage to run a 20amps for the mini-split and a 15amp for the room outlets and lights ( and garage outlets). I don't do much else in the garage besides run a circular saw.

So my questions are
Should I wire this room with 20 amp / 12/2 wire instead of 15 amp 14/2 ? I like the idea but read 12/2 can be harder to deal with in gang boxes.
Can I keep the 20amp feeder circuit for a bit - I'm hoping to get the garage part done first.

Is there any way around fixing the disconnected ground from the garage. I've read that having gfci breakers/outlets in the garage could be a work around for now? I know that the ground from garage should bond with neutral wires at the main breaker only.

Any input on all this is greatly appreciated.!

 

[wyliesdiesels]

what is the MCA- minimum circuit amps for the unit? MOCP is for the breaker rating.

you didnt state the feeder amperage rating but sounds like its only 15a. If thats the case, then putting a mini split on it and trying to run another power tool at the same time as the mini split is running may trip the breaker.

Do you have 240v or 120v feeding the garage? saying 2-wire doesnt mean anything. that could be a hot and neutral or 2 hots....

 

[u2slow]

Older Code cycles allowed a 3-wire supply supply like that. It is still legit for existing, but not allowed for new. You may have two 120v/20A circuits there. The ground would need to be hooked back up. Is it controlled by a 2-pole breaker in the main? Or a single pole? Is there an existing subpanel in the garage?

What you may want to consider for the short term is a portable heater with discrete power levels. That way you can run the full 1500W when not doing other things, and cut it back to 900w or 600w when running more lights/tools.

I started with two temporary 20A circuits to my shop also.

 

[wyliesdiesels]

Older Code cycles allowed a 3-wire supply supply like that. It is still legit for existing, but not allowed for new. You may have two 120v/20A circuits there. The ground would need to be hooked back up. Is it controlled by a 2-pole breaker in the main? Or a single pole? Is there an existing subpanel in the garage?

What you may want to consider for the short term is a portable heater with discrete power levels. That way you can run the full 1500W when not doing other things, and cut it back to 900w or 600w when running more lights/tools.

I started with two temporary 20A circuits to my shop also.

yes however he didnt state what voltage the feeder is running at. could be 120v.

Also if only 2 wires are hooked up, then he would only have either 120v or 240v but not both.

 

[markfraser33]

I'm pretty sure the feeder line is only 120V as the feeder line is running off a single pole 20 amp breaker. The mini-split mca rating is 15 amps. The garage doesn't have a subpanel right now.

 

[Noltz]

A picture of your "...the overhead wire feeding the garage looks like only 2 of the 3 wires are connected at the house," might help illustrate what's already there. And anothe picture where (or if) it's connected in the garage to anything. If it's actually 3 conductor 12 gauge you could add another 20A leg to the conductor, giving you all the power you need. Mini-split on one leg, garage on the other, no subpanel needed. But if not, or not to code you're going to be starting fresh from the breaker. Wylie has proven many times to be very good at figuring out what's going on and you'd be wise to listen. Personally I'd consider running 8/3 nmwu to the garage. That's 40 amps to a sub panel. Or 50A... I'd leave that to Wylie?

 

[pattenp]

If the OP is in the US they're not going to be using NMWU because it's a Canadian product. This is why it's important for posters to include their general location especially when asking electrical questions.

 

[wyliesdiesels]

I'm pretty sure the feeder line is only 120V as the feeder line is running off a single pole 20 amp breaker. The mini-split mca rating is 15 amps. The garage doesn't have a subpanel right now.

If thats the case, then i would just start over.

 

[Viper98912]

Read the installation manual of the mini split. While mine said it would take 13 amps max and could run on a 15 amp line, there was a line hidden inside the install manual that said to use a 20 amp circuit breaker.

If your current line to the garage is a 120V 20 amp line, you might as well run a completely new line, and go 3-wire 240V so you actually have "double" the juice running to the area (a set of breakers set on each line). So maybe do something like a 240V 30 amp line? Then you put the mini split breaker on one line and put the other room breakers on the other. Should be a simple 10/3 wire, which is available in an underground format in the event you want to dig it in.

 

[markfraser33]

Ok great thanks for the input, I'm going to look into running a 240 line

 

[wyliesdiesels]

Read the installation manual of the mini split. While mine said it would take 13 amps max and could run on a 15 amp line, there was a line hidden inside the install manual that said to use a 20 amp circuit breaker.

If your current line to the garage is a 120V 20 amp line, you might as well run a completely new line, and go 3-wire 240V so you actually have "double" the juice running to the area (a set of breakers set on each line). So maybe do something like a 240V 30 amp line? Then you put the mini split breaker on one line and put the other room breakers on the other. Should be a simple 10/3 wire, which is available in an underground format in the event you want to dig it in.

the feeder would need to be 4-wire not 3-wire

 

[Viper98912]

the feeder would need to be 4-wire not 3-wire

I wasn't counting the ground, such as 10/3 is actually 4 wires