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Thread: Mini Splits

  1. #1
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    Mini Splits

    The last few days I spent at an electrical conference in Raleigh. Over 700 people attended- contractors, ec,electricians, inspectors etc.

    We do this every year and this year it was quite good because they changed the format and more questions got answered.

    One particular question came up about mini splits and whether or not a disconnect was needed at the inside unit.

    The opinion was no disconnect was needed based on 440.8 except and 430.87 exception.

    They did bring up that many of these units have dc motors and that it would not be compliant to install a standard snap switch on a DC circuit. They stated that if you tried to turn the snap switch on under load you would be in for a surprise. They did not elaborate.

    Does anyone know anything about this. There are tons of units out there with a/c switches
    They say I shot a man named Gray and took his wife to Italy
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  2. #2
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    Can you elaborate on the "opinion". Since the motors are in a different location, I don't see 440.8/430.87 Ex 1 applying.
    I can see it for a compressor/condenser fan but not a mini-split...

    no comment yet on the DC switch
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  3. #3
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    Quote Originally Posted by augie47 View Post
    Can you elaborate on the "opinion". Since the motors are in a different location, I don't see 440.8/430.87 Ex 1 applying.
    I can see it for a compressor/condenser fan but not a mini-split...

    no comment yet on the DC switch

    I think what they are getting at is that this is one machine and thus the outside unit is the controller for the inside unit. This being the case the disconnect only has to be within sight of the controller
    They say I shot a man named Gray and took his wife to Italy
    She inherited a million bucks and when she died it came to me
    I can't help it if I'm lucky



  4. #4
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    I've never seen or installed one in my life in a resi setting.

  5. #5
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    I always wondered if the indoor unit of the mini-splits really were considered something that could be serviced anyhow. I guess I haven’t looked real hard at them since the hvac guy does most of the work hooking up.

  6. #6
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    Quote Originally Posted by peter d View Post
    I've never seen or installed one in my life in a resi setting.
    They get used alot around here for small areas in an addition or if the attic area gets finished they put one there. Very efficient but perhaps not in the North
    They say I shot a man named Gray and took his wife to Italy
    She inherited a million bucks and when she died it came to me
    I can't help it if I'm lucky



  7. #7
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    Quote Originally Posted by Dennis Alwon View Post
    I think what they are getting at is that this is one machine and thus the outside unit is the controller for the inside unit. This being the case the disconnect only has to be within sight of the controller
    I understand the single machine argument but 450.87 does not seem to support the idea, IMHO
    At my age, I'm accustomed to restaurants asking me to pay in advance, but now my bank has started sending me their calendar one month at a time.

  8. #8
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    Quote Originally Posted by Dennis Alwon View Post
    They did bring up that many of these units have dc motors and that it would not be compliant to install a standard snap switch on a DC circuit. They stated that if you tried to turn the snap switch on under load you would be in for a surprise. They did not elaborate.
    I would think that turning the switch off under load would be much more interesting, as DC is more likely to cause arcing, since there is no zero crossing which helps extinguish the arc.
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    Larry B. Fine
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  9. #9
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    Quote Originally Posted by LarryFine View Post
    I would think that turning the switch off under load would be much more interesting, as DC is more likely to cause arcing, since there is no zero crossing which helps extinguish the arc.
    He may have said turning it off under load-- I don't recall
    They say I shot a man named Gray and took his wife to Italy
    She inherited a million bucks and when she died it came to me
    I can't help it if I'm lucky



  10. #10
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    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.

    The motor may be a DC motor but the question about a typical AC toggle switch not being rated for DC becomes a question of whether it is interrupting DC or not. If the rectifier is in the outdoor unit then it is wrong to use a switch only rated for AC. I don't know enough about what is typical for these units to know where the rectifier is located.
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