Split Unit Air Conditioner Disconnect Requirements

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cohosilver

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What are the requirements for the disconnecting means of a split unit air conditioner? I am in a location where thousands upon thousands of these units are installed and I have seen them connected many ways including being hardwired in a splice box at either the blower unit or the compressor, a fixture whip attached to a cord cap and a receptacle at either the compressor or the blower unit, a single pole 20A toggle switch located at wither location, or a 60A 250V disconnect with a 20A QO circuit breaker that is capable of being locked out, mounted either inside with the blower or outside with the compressor.

There are different voltages in use at this location, generally the voltage is 230/380V 50 hz European but there is also 120/240V 60hz. The split units are in general either 9000BTU units or 18,000BTU units and in general they draw approximately 12-14A single phase 230V with between 20-32A start up.

The electrical panels that feed these stlye of units are often not on the same structure or building as the air conditioning unit.

Is it okay to mount a 60A 250V rated air conditioner disconnect with a 20A single pole 120/240V 240V rated QO style circuit breaker inside a structure next to the blower portion of the unit where the feeding circuit is line/loaded through the disconnect to a 12/2 SO cord "fixture whip" to the blower portion of the unit (where the jumper leads are then sent to the compressor) so that the air condtioner can be locked out inside and the service technician can then safely work on the compressor outside? The voltages would be 230V single phase and there would be either a European Style circuit Breaker such as ABB, Hagar, Merlin Gerin at the panelboard or loadcenter or something such as a 277/480V 600V rated Square D NF load center and circuit breakers.

Consider that there are thousands and thousands of these types of units here and this question is inquiring about a standard practice that meets NEC 2008 requirements including the 230/380 voltage.
 
augie47

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
cohosilver, From your original post, I will assume you may also be talking about other than ductless units. Unsure about Oregon, but here we enforce the inside, airhandler, under Art 422. Most of them fall under 422.119(A)(2) and, due to the motor, require a disconnect within sight.
It can be fusible, non-fusible (if correct protect is provided elsewhere), breaker or switch rated per 424.19 (125%).
The "cord connection" between the disconnect and unit is not permitted here.
The outside unit with the compressor is covered locally by Art 440.
That disconnect must also be in sight and rated per 440.12 (normally 115% of the branch circuit selection current)
 
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Ragin Cajun

Senior Member
Location
Upstate S.C.
OregonSE said:
http://cbs.state.or.us/bcd/boards/electelv/board_pack/09/20090924/EE_092409_IVa.pdf
Click to expand...

I assume they are addressing units such at the Mitsubishi Mr. Slim Split-ductless units. They are a heat pump but from what I see in the literature, have NO strip heat. The indoor fan is powered from the outdoor unit. The connection requires three generally #14 plus a ground.

Since they are a rather compact unitized assembly, providing a lockable disconnect is a problem. Oregon's stand is very interesting. That will really simplify installation and save $$!

I have several projects about to go out where these units are being used. But, will the local AHJ's here go with Oregon's stand.

RC
 
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One-eyed Jack

Senior Member
Location
Scotland Neck, NC
Ragin Cajun said:
I assume they are addressing units such at the Mitsubishi Mr. Slim Split-ductless units. They are a heat pump but from what I see in the literature, have NO strip heat. The indoor fan is powered from the outdoor unit. The connection requires three generally #14 plus a ground.

Since they are a rather compact unitized assembly, providing a lockable disconnect is a problem. Oregon's stand is very interesting. That will really simplify installation and save $$!

I have several projects about to go out where these units are being used. But, will the local AHJ's here go with Oregon's stand.

RC
Click to expand...

Quite a few of the mini-splits have and indoor fan that is less than the 300 va min for the required disco. 422.31 As such the branch circuit ocpd would be adequate. Lockable outdoor disco would not be a problem.
 
H

hurk27

Senior Member
Location
Portage, Indiana NEC: 2008
I have wired several of the Carrier types, and they require a 12/3 cable or conduit between the units, and can be fed from either end, the red is used to bring on the compressor, when we feed these to the outside unit we use a standard AC 30/60 amp pull out disconnect, as the covers are lockable this meets the requirements of having a lockable disconnect out of site. never had a problem with it. you could also use a 4-wire twist-loc at the inside unit for a local disconnect, but we have never been required to do that.
 
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dbuckley

Senior Member
Location
Canterbury, New Zealand
In 50Hz-land these units are very popular, mainly of Japanese manufacture, and there is no regulatory requirement for a disconnecting means between the two parts of a split unit. Furthermore, these units are not designed to have such an isolator, and any such use of an isolator would violate the manufacturer's installation instructions. The general method of installation is an isolator outside with the outdoor unit. Better installers use an isolator cvapable of being locked (though mine didnt!)

It is different under the NEC and the equipment designed to be installed in compliance with the NEC is (in my limited experience) different.
 
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cohosilver

Member
Split Unit A/C Disconnect Requirements

Split Unit A/C Disconnect Requirements

The "typical" installation that I see here is a 3 conductor 2.5mm pvc cable with either a British 13A plug or a German "Shuko" two pin cord cap, this is similar (loosely termed) to 14/2 NM cable used as a fixture whip, from the air handler to a "European" multi-adaptable receptacle. From the air handler to the compressor another 3 conductor 2.5mm pvc cable is run with the hoses to the compressor to power the compressor. At the compressor there is no disconnecting means, just the compressor. I am attempting to bring the present installations into compliance with 2008 NEC. The units are ductless units and there are no heat strips with these units. The most common manufacturer of these type of units where I am at is Chigo.

It seems from the Oregon article that an AC disconnect switch (Square D QO200TR or similar) needs to be located at the outdoor compressor/condensor. It is very typical installation for the power from one portion of the A/C unit carry to the other, power would then go through the disconnect to the compressor and from the compressor to the air handler, via a UL listed cable, possibly 12/3 SOJ cord, to the air handler?

I still have questions. Too bad I couldn't get one of the Mike Holt drawings that simplify the matter.
 
augie47

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
It does sound as if you have the units similar to the ones described by OregonSE. He can elaborate on the wiring method acceptable there, but we would not accept a cord of any type to interconnect as it would be viewed as a violation of 400.8
 
H

hurk27

Senior Member
Location
Portage, Indiana NEC: 2008
I still have questions. Too bad I couldn't get one of the Mike Holt drawings that simplify the matter.
Click to expand...


Kind of like this?




attachment.php
 
M

macmikeman

Senior Member
Location
Planet macmikeman
Here is my take as I see it, and if my history holds up, I could very well be wrong...... Air conditioner " systems" are considered in chapter 440 to be one machine. If the compressor gets the feeder first and then feeds the fan coil unit, a lockable disco at the compressor *within 50 foot and a direct line of sight of the unit* should suffice for the disco means for the interior fan coil unit. If you have inspectors who are able to read chapter 440 or are willing to try, the use of the three pole switch and its expense should be unnecessary. When wiring refrigeration units such as walk in coolers, then it is not considered as one machine and the fan coil unit will require its own disconnect. Getting the two confused leads to misapplication of codes for the ac units. I'm here to learn, so if I do have it wrong, have at me:)
 
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