Mini Split AC electrical

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Old 08-12-15, 01:14 PM
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Mini Split AC electrical

Hello, I have a 110v 1ton unit that needs 10 gauge power and 14 gauge control wire. Can they be in the same conduit and if so how large of a conduit is needed without any derating? Can the control just be 4x14 thwn instead of a special minisplit cable?

The indoor unit is powered from the outdoor unit over the 14/4

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Old 08-12-15, 02:07 PM
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The manufacturer's installation manual should specify which wiring is field provided and which is part of their unit or an assembly you must get from them. I have seen a variety of specifications for the wiring between the inside and outside unit -- depends on which ones you have. The mfr should provide minimum circuit ampacity (MCA) and maximum overcurrent protection device (Max OCPD) for the supply circuit. The supply circuit and control wires cannot be in the same conduit.
 
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Old 08-12-15, 03:10 PM
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15 MCA, 25 OCPD

It's not 240, straight 120.

It says 14/4 back to the indoor

Blue/Black/Brown/Ground on the interconnect

White/Black or Red/Ground to the outdoor

Can't put the interconnect in the same conduit

Gree 12,000 16seer unit
 
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Old 08-12-15, 04:22 PM
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Blue/Black/Brown/Ground on the interconnect
That's three wires and a ground.

With split units.... power goes to a service disconnect at the unit then to the condensor.

I use 14-3 UF cable and the cable follows along with the refrigerant and drain lines. The control cable comes in the back of the inside unit..... in the same opening as the refrigerant and drain lines.

The colors between the two units is of no consequence..... however you will see the numbers 1,2,3, and G. You must connect the same color to the same number at both ends.

Based on the Cree install manual and using 14-3 w/gr. UF cable between units.

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And a word to the wise...... be sure you are familiar with the manufacturers warranty and the warranty policy from the place of purchase. Many times warranty and warranty repair is based on installation by an authorized installation company.
 

Last edited by PJmax; 08-12-15 at 08:23 PM. Reason: added wiring coloring info
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Old 08-13-15, 06:07 AM
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I know NM is a no no outdoors, but can I run it to the disconnect and then switch to thwn? Technically there would be 6in of NM in an outdoor enclosure?

I'm not too concerned about warranty, unit and some of the install cost will be free after rebate
 
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Old 08-13-15, 06:24 AM
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To answer my own question, it sounds like the Pros run NM to them but that may not be to the letter NEC? To be safe I could just run 10/2 UF to the disconnect?
 
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Old 08-13-15, 06:58 AM
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The NM can go into the back of the disconnect. I usually cut a 2-3" piece of conduit screwed into the back of the disconnect, hole saw a 1" hole into the house and sleeve the NM through that. Fill in all the gaps with great stuff or caulk. You could use UF if you wanted.

No need for the supply circuit to be #10. According to the MCA this can be #14, #12 if it's a particularly long distance roughly 100' or more from the panel. I'd install a 20A breaker.
 
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Old 08-13-15, 07:00 AM
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This is the breaker I want isn't it? For a Square D QO panels

Square D, QO 25 Amp Single-Pole Circuit Breaker, QO125CP at The Home Depot - Mobile

Seems odd none of my local half dozen store HD/Lowes have it in stock but the one HD/Lowes in a different smaller area does
 
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Old 08-13-15, 07:04 AM
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The manual says 10awg? 25amp breaker

http://www.homedepot.com/catalog/pdf...fa4d0ffb33.pdf

The 12k 115v model
 
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Old 08-13-15, 07:40 AM
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Indeed it does -- lots of contradictory instructions in that manual. Maybe contact them for clarification, or just use the #10. It won't hurt anything other than your wallet.

Usually with the max OCPD you should start with the smallest breaker to satisfy the MCA (15A in this case), and increase until you get to the Max OCPD if the unit will not start up without tripping the breaker. You can jump right to 25A, but it's generally best practice to try the smaller ones first.

This one is also a gem of confusion: Interconnecting Cable: Recommended cable - 14/4 AWG stranded bare copper conductors THHN 600V unshielded wire
 
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Old 08-13-15, 08:05 AM
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Do you conduit the 14/3 UF indoors? And just run it through the LiquidTight 1/2in outside with the main power?
 
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Old 08-13-15, 07:25 PM
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You do not need to run the UF in anything. The UF follows and gets taped or tied directly to the refrigerant lines. The control cable doesn't need to follow the main power cable.

Most installations look like below. The AC comes to a service disconnect and then to the unit in Sealtite. There will be a second knockout next to where the power enters the unit for the control cable. The yellow/orange lines are the refrigerant lines. The black is the UF. The gray is the drain line.

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Since most of the time I wire the system installed by an A/C contractor..... the lines between the two units are covered in a plastic covering that looks like a gutter downspout pipe.
 
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