Mini-Split Disconnect??

[iwire]

This is not a because I said so thing.

The NEC requires it even if your inspector does not.

Running the provided cables through the walls is also an NEC violation.

And yes the HVAC guys can choose to not get the cable with the unit.


The pictures are of typical split systems with outdoor condenser units.

 

[infinity]

I have never installed one of these but may need to in the near future. So what's the problem with the cable?

 

[iwire]

I have never installed one of these but may need to in the near future. So what's the problem with the cable?

Gus seems to have the details but if they claim it is article 400 cord it can't be run in walls or used as a substitute for chapter 3 methods.

If they claim it is type TC cable then it needs to be in a raceway.

It is not NM cable.

As I mentioned, the HVAC guys I work with don't even buy the wiring kit, only the copper refrigerant line set with the indoor and outdoor units.

 

[infinity]

Gus seems to have the details but if they claim it is article 400 cord it can't be run in walls or used as a substitute for chapter 3 methods.

If they claim it is type TC cable then it needs to be in a raceway.

It is not NM cable.

So it's a cable between the two units that's provided by the manufacturer if you choose to purchase it from them?

While we're on the subject anyone have an opinion as to who is the best manufacturer of these units?

 

[iwire]

So it's a cable between the two units that's provided by the manufacturer if you choose to purchase it from them?

Yes, that is my experience anyway.

Typically you run just one branch circuit from the panel out to the outdoor unit via the outside disconnect. Then you run that cable or a chapter 3 method from terminals inside the unit that run back inside the building to the indoor unit. If you shut off the outdoor disconnect it will also kill the feed to the inside unit.

Typically it has been three circuit conductors, two at line voltage for fan power and one at low voltage for control. Sometimes the control is just basic on or off or sometimes it is a data signal imposed onto the lines.

While we're on the subject anyone have an opinion as to who is the best manufacturer of these units?

They all suck to wire.

Very small space and designed for that cable we spoke of, not MC or FMC.

 

[Strathead]

Has anyone taken a look inside the unit? I am install over 120 of them on two projects right now and I am installing a disconnect per the Engineer. I have installed some in the past where the Engineer didn't specify a disconnect, but I put one in anyway. Now for the question above. It the motor has a plug connection on it then it would explain why the manufacturer doesn't show a disconnect.

 

[david luchini]

Has anyone taken a look inside the unit? I am install over 120 of them on two projects right now and I am installing a disconnect per the Engineer. I have installed some in the past where the Engineer didn't specify a disconnect, but I put one in anyway. Now for the question above. It the motor has a plug connection on it then it would explain why the manufacturer doesn't show a disconnect.

Most of the mini-splits that I've dealt with, 422.31(A) would preclude the need for a disconnect at the indoor unit.

I think the interconnect between the outdoor unit and the indoor unit would be a Class I circuit rather than a branch circuit, but I don't know what effect that would have on disconnect requirements.

 

[augie47]

Honeywell came out with a "min-split cable" which they were supplying for such systems. In their advertising brochure (https://www.honeywellcable.com/CatalogDocuments/LMSCBLIFDMiniSplit_final.pdf) they pointed out the "cord"was prohibited for such use by Art 400. The did not point out that their cable was a type TC cable and, when used in a residential installation, was only allowed in a raceway.
When question by a local AHJ they had no argument.

 

[iggy2]

View attachment 10469 View attachment 10470
Notice no disconnect between indoor and outdoor units

I would imagine those instructions also somewhere say "comply with applicable local codes."

 

[iggy2]

I guess it's an interesting argument. The one we have in our office doesn't even have an access on the bottom or side for any way to tie any kind of conduit or cable etc. They are designed to install the factory provided cable along with the set line straight into the back from the exterior of the wall/building where the condenser is. And the fact is that we have installed A LOT of these all over SWFL and not one has a disconnect on the inside...I have never heard or have yet to see one like that installed by anyone. I would actually be curious to see a picture of that type of installation if one of you guys wouldn't mind posting one. Also, what about voiding any warranty for the equipment by cutting the cable provided as well as drilling a hole in the side of the interior unit?? I don't know man, seems just totally impractical, and according to 110.3(b) it SHALL be done the way I do it to be CODE compliant. :?

Since the indoor and outdoor units are typically not too far from each other, why not run the main power to an indoor disconnect first, then continue on to the outdoor unit disconnect? Shutting off the indoor disconnect would then shut both items down - but would be a compliant service disconnect.

I know this is not how it's done, or contemplated by manufacturer, but it seems the best way to do it w/o having to violate the warranty or listing by modifying the unit or cabling to add a switch leg at the fan unit.

And I'm assuming that these do not have a switch with definite 'off' position, and could be considered an appliance???

 

[mgookin]

It sounds like it's a matter of what you call the cable running from the condensor to the AHU. If it's part of the appliance then OP has a logical argument.

Imagine one day when we stop running the condensor in our refrigerator inside the air conditioned living space then spend more money to move that same heat again to outside the living space. We will have an outdoor condensor and indoor refrigerator. If GE or Maytag supplies that cord, is it subject to NEC?
Will we need a disconnect in the kitchen at the refrigerator?

I'm not saying this is the answer, but it is certainly worthy of discussion.

I still say OP should go back to the manufacturer's rep for the answer.

 

[boltneck]

Since the indoor and outdoor units are typically not too far from each other, why not run the main power to an indoor disconnect first, then continue on to the outdoor unit disconnect? Shutting off the indoor disconnect would then shut both items down - but would be a compliant service disconnect.

I know this is not how it's done, or contemplated by manufacturer, but it seems the best way to do it w/o having to violate the warranty or listing by modifying the unit or cabling to add a switch leg at the fan unit.

And I'm assuming that these do not have a switch with definite 'off' position, and could be considered an appliance???

^^ this is exactly what I do...and just use a 2 pole switch

 

[macmikeman]

^^ this is exactly what I do...and just use a 2 pole switch

As I recall that was a ''It's time for your mactip of the day!'' #37 I believe, first published many many years prior to now..........



However it was bested by '' It's time for your mactip of the day'' #78 that taught dear readers to install one of the carlon adjustable depth single gang boxes in the location for the indoor disconnect switch, and to screw adjust it all the flush to the face of the stud so it could be drywalled right over. LOOP the connecting cable thru the box that runs from compressor to fan coil. And record the exact location of your disconnect box so that later if you get hit by a really akamai inspector who understands that it is an actual nec requirement (hats off to iwire for his effort to make it known to the community, it is a motor after all...) you can dig it out later and adjust the depth back to flush with the surface of the surrounding drywall and install that pesky two or three pole switch depending on the make and model.

 

[gadfly56]

As I recall that was a ''It's time for your mactip of the day!'' #37 I believe, first published many many years prior to now..........



However it was bested by '' It's time for your mactip of the day'' #78 that taught dear readers to install one of the carlon adjustable depth single gang boxes in the location for the indoor disconnect switch, and to screw adjust it all the flush to the face of the stud so it could be drywalled right over. LOOP the connecting cable thru the box that runs from compressor to fan coil. And record the exact location of your disconnect box so that later if you get hit by a really akamai inspector who understands that it is an actual nec requirement (hats off to iwire for his effort to make it known to the community, it is a motor after all...) you can dig it out later and adjust the depth back to flush with the surface of the surrounding drywall and install that pesky two or three pole switch depending on the make and model.

OK, points for being fiendishly clever, but holy cow! wouldn't it be easier to just install the dang switch?

 

[texie]

I've always thought as iwire that a disconnect is required at the indoor fan/coil unit of a mini-split. But david's comment back in post #27 that 422.31(A) would apply in most of the smaller units seems to be correct. What say all?
As far as the factory cables often not being compliant with NEC, what have we come to as far as NRTL value? This has been an issue since these units came to market. Why don't the NRTLs care? And the instructions that typically come with these units are an insult!

 

[SceneryDriver]

Honeywell came out with a "min-split cable" which they were supplying for such systems. In their advertising brochure (https://www.honeywellcable.com/CatalogDocuments/LMSCBLIFDMiniSplit_final.pdf) they pointed out the "cord"was prohibited for such use by Art 400. The did not point out that their cable was a type TC cable and, when used in a residential installation, was only allowed in a raceway.
When question by a local AHJ they had no argument.

Listings are what they are, but it staggers me a little to think that TC cable can't be used without a raceway in residential settings. I just finished a job with TC cable; it's like NM, but with a jacket on steroids. It's certainly no more fragile than NM; I'd say it's actually much tougher. There seems to me to no reason, other than vendor paperwork, that TC couldn't be used anywhere NM can.



SceneryDriver

 

[macmikeman]

OK, points for being fiendishly clever, but holy cow! wouldn't it be easier to just install the dang switch?

We here in the land of Aloha have some inspectors demanding the 3 pole switch to be installed to open all three legs of the control cable between units. That is a thirty dollar device around these parts. I am of the tribe that feels a locking disco on the outside unit is protection enough from electrocution for the service man. 5 bucks for a carlon adjustable box vs thirty for a 3 pole sw. It gets me thru rough in inspection. They tend to miss it on final inspection. Only had to go back to install the switches on one job out of a hundred I set up this way. Insurance....

 

[Ragin Cajun]

Then there is the issue of the little condensate unit that needs 120V. I assume providing a duplex outlet neat the AHU?

Some pictures in this thread show the unit, some a sloped drain line, and other neither - depends on how installed and if it's on an outside wall.

I guess I need to add to my "standard" detail power for the condensate unit via a duplex outlet!

NEC calls for a lockable disconnect. A typical toggle switch is not lockable? Now what do you do?

I sure agree on needing "standards" so all of know what to include in the bid. If there are a bunch of these, doing it "right" could lose the job against someone who doesn't include the switch and/or the receptacle, etc.

From what I recall the AHU motor is usually a small 120V motor, but I guess it could be 208V, etc. for a three phase unit. What have you seen in the field?

Regarding the "third" wire which is for control. Anybody know what voltage? Does it really need to be disconnected? Makes a big difference between using a simple two pole switch and a more expensive 3 pole motor disconnect, etc.

Arggggg. :rant:


RC

 

[iwire]

Listings are what they are, but it staggers me a little to think that TC cable can't be used without a raceway in residential settings.

Put in a proposal, or should I say give some public input.

 

[iwire]

Regarding the "third" wire which is for control. Anybody know what voltage? Does it really need to be disconnected? Makes a big difference between using a simple two pole switch and a more expensive 3 pole motor disconnect, etc.

It depends on the unit itself.

Sometimes the third wire carries a data signal and provides much more than just a run signal to the outdoor unit. (error codes, outdoor temp displayed indoors etc.)

Other times all it is a low volt DC signal that turns the compressor off and on nothing more.


I do not believe we are required to break that one but sometimes I do.