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Thread: Mini Splits

  1. #21
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    Quote Originally Posted by Dennis Alwon View Post
    I am not sure this is accurate as many of these units are run with T-stat wire between the indoor and outdoor units. I have seen the line voltage units also and I agree that they are fine wired with 14/3 nm or whatever.... But some of these units are run with low voltage to the indoor unit
    Well I don't doubt that at all. There are many variations especially now that off brand Chinese units are more and more common.

  2. #22
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    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.
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  3. #23
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    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
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  4. #24
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    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.

  5. #25
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    Quote Originally Posted by goldstar View Post
    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.

    They may do that to cover their butts. It may say a disconnect may be required IDK.
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  6. #26
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    Quote Originally Posted by kwired View Post
    I have never noticed 440.8 before, but is one more thing that should allow not requiring a disconnect for inside portion of this system.

    My thought has always been that 440 only applies to items with a hermetic compressor, it mentions this in 440.1.

    The indoor unit, unless the whole system is deemed a single unit, does not contain a hermetic compressor and therfore IMO does not fit in the scope of 440. It is simply a motor operated appliance and is covered by art 422. They also are typically under 300 VA or 1/8 HP and 422.31 allows the branch circuit device to be the disconnecting means, and does not require it to be within sight.
    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.

  7. #27
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    Quote Originally Posted by tortuga View Post
    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.
    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.
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  8. #28
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    Quote Originally Posted by tortuga View Post
    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.
    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.

  9. #29
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    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.
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  10. #30
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    Quote Originally Posted by Andy Delle View Post
    There is no reason 12-14/3 NM, BX, AC can't be used for that. The expensive cables the manufactures sell is in no way specially shielded either that I have seen...../snip....Are these cables even listed for in-wall use under the NEC?
    Quote Originally Posted by Andy Delle View Post
    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.
    Quote Originally Posted by kwired View Post
    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.

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