Andy Delle
Senior Member
- Location
- Los Angeles CA
Well I don't doubt that at all. There are many variations especially now that off brand Chinese units are more and more common.
Mini Splits
- Thread starter Dennis Alwon
- Start date
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Well I don't doubt that at all. There are many variations especially now that off brand Chinese units are more and more common.
macmikeman
Senior Member
- Location
- Planet macmikeman
Around my coconut tree there have been many inspectors demanding the indoor switch, although not as many lately as the older guys retire out. So macmikeman invented some brilliant ways to handle the interior disconnect switch, or more exactly what you should do if you think one may become demanded by the inspector at time of final. You know those adjustable depth single gang boxes Carlon sells? Put one someplace acceptable near the fan coil unit at rough in time. Run the (ac) 14-3 cable in and out of that box and then on over to where the fan coil connection will be (I like to stuff a foot or so of that 14-3 down the drain pipe the ac guys put in so hoping they hook up the wire for me when they install the fan coil unit) , without any splice and just fold up the cable inside the box all nice. Mark the location of the box exactly on your plans very carefully. Now screw the box so it is flush with the face of the stud. Let em drywall right over it. I like to put a piece of painter's tape over the box and write "bury me" on it. Now after drywall, paint, and indoor fan coil has been installed, wire the fan coil up and ignore the switch box for now. At final , if the inspector throws a red flag at you, get your plans out, cut out the exterior of the blue box with a drywall knife very carefully, set the impact gun to reverse and bring the box out flush. Install the proper disconnect switch into the box. Put a faceplate on it. No muss, no fuss. ( So far I only had to do this 2nd part of the operation to keep an inspector happy once , out of preparing for it maybe 50 times to date.
JFletcher
Senior Member
- Location
- Williamsburg, VA
Communication cable can absolutely be spliced and not lose any speed or bandwidth if done correctly. They make Cat5e and Cat6 splice blocks, they are 4 to 7 dollars each and probably come with a little plastic 110 style punch down tool if you don't have a nice proper one. Not that you will probably ever need it for a mini split but if you ever have a data cable that gets cut...
And thank you for the detailed tip Mike much appreciated
And thank you for the detailed tip Mike much appreciated
goldstar
Senior Member
- Location
- New Jersey
- Occupation
- Electrical Contractor
Manufacturers of some of these units show the inside disconnect switch in their drawings. I believe Mitsubishi is one of them (from what I remember). If that's the case I believe you would have to install one irrespective of whether it's required by Code or not.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Agreed this is a key point and makes clear sense to me. No indoor disconnect is required by the NEC.
Having looked at many residential mini split installs I have never seen an outdoor with a rectifyer or fuses or anything other than a plain jumper between the LINE L1 and L2 and the LOAD L1 and L2 to the indoor unit. The 3rd wire is data. No fuses or anything.
So now we have a 14AWG "tap" on a 20, 25 or 30A breaker. My understanding is the reason the manufacturers use Tray cable type TC between the indoor unit and outdoor unit is TC is marked 90C THHN unlike UF or NM-B, they use the higher ampacity to not have to fuse the 14AWG wire on a 30A breaker.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
I haven't been involved with all that many of these units, but seems every one I did do only was supplied with a 15 amp breaker so the size of conductor in relation to OCPD was never an issue.
Andy Delle
Senior Member
- Location
- Los Angeles CA
Well code issues aside, it's not really a hazard to have 14awg on a 30a breaker in this application. There are no doubt fuses or some form of OCPD on the indoor unit. 14awg shorted will still trip a 30a breaker, probably even a 50a. And there is very low likely hood anybody would pull a branch circuit from the indoor unit.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
With motors and/or AC equipment it is possible to have MCA that only requires 14 AWG and 30 amp OCPD, or even 35 or 40 amp OCPD in some cases.
Gentleman forgive me as I am missing something and its been a long day.. Using NFPA 2017 NEC how do you come up with a 20A rating for 14/3 UF cable or NM-B cable (334.80)? and I am also looking at ( The expensive cables the manufactures sell ) Tray Cable type TC 14AWG is listed as THHN 90C rated 25A @ 90C (392.80) so I need some enlightenment as to how we can connect any of these to an inverse time residential 30A breaker?
I have looked at many of these minisplits and I see none that have a internal fuse between the outdoor units and the indoor unit.
Thank you in advance.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
My guess is 240.4(G).
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Look at the asterisks next to 14, 12 and 10 and then look at the section Larry stated
Right thank you, I still don't come up with 30A for a 14Awg circuit to the indoor blower unit.
Are you saying like this:
- 240.4(D) -> 240.4(G)-> selecting 'Motor operated appliance circuit' from the table
- 422.11 -> 422.11(G) applies Sends us to part III (and only part III) of art 430.
- 430.33 applies and that finally sends us to table 430.52 in Part IV of 430.
- We have a at most 1/6 HP blower (squirrel cage) motor so thats 2.2A @ 230V T430.248
- Go to the table for inverse time breaker in 430.52 = 250%
- OCPD is 2.2A * 2.5 = 5.5 Amps
- Next standard size inverse time breaker 15A (240.6)
Andy Delle
Senior Member
- Location
- Los Angeles CA
Note that I said "code issues aside". The point is that it is done in the field daily and while technically a violation, it is not that unsafe IMO. The indoor fan is not going to pull more than a few amps. And if there is a short, a 30a breaker will still trip with 14awg attached and no damage to the wire.
It's a closed system and that's why some inspectors may overlook the issue altogether.
I expect the NEC will look at this sooner or later. Too many question here and on other forums regarding minisplits. Classic split systems are pretty clear as to OCPD requirements on each end but minisplits have this unique wiring scheme for the indoor unit.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
The overcurrent protective device for the unit is there only for short circuit and ground fault, the unit itself has overload protection built in which will protect the wire. The load at the unit still cannot be more than 15 amps for a 14 gauge if you use nm cable. If the 14 wires is rated 75C then you can use the wire at the 20 amp capacity. The overcurrent protective device, however, can be higher
Yeah am totaly with ya, I was playing UL product evaluation engineer up there.
Since they are UL listed units someone has gone thru the calcs and decided its safe.
I find it fascinating that part of a branch circuit that goes in walls is designed by a UL product listing.
It would be like a light and a switch being sold together and the instructions saying I can install the light on a 20A circuit and run 14AWG for a switch loop.
Whomever was the designer used the NEC, and I would like to retrace their logic.
I agree we install them often. As Kwired said the most common installs are a 15 or 20 which then there is no issue in my mind.
I don't know that its a violation to use the tray cable, that line hide stuff is the "tray". I just observed a single Daikin 30A outdoor units design has no additional protection for the 14AWG leading me to call it a tap. Other brands may have internal protection. I would be really interested to see what others find on 30A units. Do other brands have internal overloads or OCPD for the indoor unit feed?
I hope so. They are UL listed so electrical contractors liability ends with following the instructions. It seems there is a class 2 power supply and a lot of electronics in them as well. if I was conducting forensic electrical fire investigation and traced a house fire to a indoor unit I would be very interested as to what kind of OCPD it was ultimately protected by.
Yes and I imagine we did not cover all the possible ways it may be allowed. For example it could be argued that the 14AWG "tap" does not even meet the definition of branch circuit and is part of the appliance.
Yes I agree Dennis, however most respectfully do you agree the maximum rating of the inverse time breaker (regular residential plug in HACR breaker) should be determined by using Table 430.52?
We all seem to agree that the indoor blower is an applianceand the "tap" conductors does not need the switch so hopefully that helps others.
Cheers
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Mini splits are designed to work together so they are considered one unit. Why would you use 430.52 if the nameplate states what is compliant?
It depends if the 14-3 are branch circuit conductors or not.
Andy Delle
Senior Member
- Location
- Los Angeles CA
I would say no. They are not a branch circuit but rather past of a closed system. You won't be attaching other loads to this feed? Now the AHJ may see otherwise.
And then consider a condensate pump
Some units have this built in. But if not I think that's another separate 15/20a circuit. Plus it will give you a service utility outlet. I guess you could pull 14/4 with a neutral for a service / condensate pump outlet but now you would clearly be in violation IMO with a 20 or 30a system disconnect.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Here is NC official interpretation of the mini split disconnect
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