DIY Minisplit needing 8/2 wire???

[ndfastang]

Hey all. I'm insulating my 30x48x11 pole barn with R19 in the walls, and R38 or 42 in the ceiling blown in. I'm wanting a mini split because the 12,000 unit we have in our game room works great plus I don't have gas out there and want AC and cell phone control so a Minisplit fits perfectly. The Mr Cool 34,400 units are just under the 36,000 size that their guide indicates needing 40 amp and 8/2 wire. Who is using the 8/2 vs. 10/2 on these units? I know the smaller ones can go 10/2 on a 30 amp but I don't want to undersize. My lift that is rated at 17 amps keeps popping my 20 amp breaker so I don't want the same problem with the Air setup. I want to wire it once and be done. I'll have about 20ft of wire from the box to the cutoff box and another 3 feet from there or so to the unit. What are your guy's experience with these bigger units?

Thanks
Dave

 

[ndfastang]

Disregard. I found all I need in another thread searching back. I'm going to run the 10/2 and a 30 amp breaker.

 

[bored350]

For a difference in cost of roughly $10 for wire, is it really worth not following the manufacturer's instructions of using 8/2? Sure, you could probably get away with 10/2 but you yourself mentioned the issues you have with the lift which you don't want to repeat.

Sent from my moto g stylus using Tapatalk

 

[yeldogt]

my 30k is on 40 w/ 8

i would use what is required

 

[mike93lx]

if they say you need a 40 and 8/2, run it. cutting corners on this isn't smart.

 

[justinjoyal]

MCA for that unit is 25A, so a 30A breaker with 10/2 wiring is gonna be fine. But..

For HVAC applications, unless things changed recently(?), NEC allows for the MOCP breaker size to be used with MCA wire size, in your case a 40amp breaker could be used with 10/2.

 

[ndfastang]

Justinjoyal, that was the answer I was looking for. You know the unit and it's requirements and what I needed. I was told these are not a load motor setup that hits high amps on startup like a standard house HVAC unit.

Thank you Sir!

 

[yeldogt]

Justinjoyal, that was the answer I was looking for. You know the unit and it's requirements and what I needed. I was told these are not a load motor setup that hits high amps on startup like a standard house HVAC unit.

Thank you Sir!

you can call it anyway you want ...

But the codes say --- follow the manufacturers. I'm at a loss why you would even worry about the tiny difference in cost.

The units do indeed start slow --- but they also ramp up quick .. especially in the winter.

 

[justinjoyal]

you can call it anyway you want ...

But the codes say --- follow the manufacturers. I'm at a loss why you would even worry about the tiny difference in cost.

The units do indeed start slow --- but they also ramp up quick .. especially in the winter.

The manufacturer provides MCA and MOCP data, that’s it. It does not tell you what kind of wire or breaker you gotta use.

 

[ericm]

Mr Cool DIY has wire gauges and breaker requirements listed in their install manuals.

If the OP's Mr Cool is a multi-head model, it appears that the wire and breaker requirements are larger than the single head. For example a 24k+9k unit (which has a 36k condenser) requires 45a and 6g while a single head 36k unit requires 40a and 8g.

If there's a question, I'd either go with the larger size or contact the seller or manufacturer for clarification.

 

[yeldogt]

The manufacturer provides MCA and MOCP data, that’s it. It does not tell you what kind of wire or breaker you gotta use.

Both my new Carrier and the bigger Mitsubishi had the breaker size ?

 

[justinjoyal]

« Max » breaker size only. Does not mean it’s needed or better.