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  1. #14
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    MCC insures enough current is available to start without neusence trips.

  2. #15
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    Thread Starter
    What do you mean?

  3. #16
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    The unit has a MCC size. Your not allowed to exceed that.
    The thermal overload is to protect the compressor from excessive heat, not Amperage. You can install a smaller breaker and chance Nuisance trips but WHY?

  4. #17
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    Quote Originally Posted by RR449A View Post
    I m not installer, I don't install Products myself, others do it for me.
    I decide which condensing units + evaporators are going to be installed.
    I also decide which electrical panels which contain circuit breakers and contactors are going to be used.

    Since I am the one who could have problems if the compressor burns out, I would like to Know why are some people telling me that the circuit breaker should be set by MCC, when this current is nowhere to be found in the operating envelope.

    Bitzer says:





    That makes sense to me since MOA is what we find in the operating envelope.

    But, then again, Bitzer also says this:



    I am totaly confused.

    P.S. I am not allowed to post links, therefore, I cannot put a link to a quoted document.
    From what I am able to surmise, you are directing the installation of manufactured equipment.

    The information I talked about is on the label.

    That is the ONLY information you can use and be in code compliance.

    Have your men size the co0nductors and the protection according to what I explained. Any good electrician will know what to do.

    If you do not know which table to use in the NEC, you must consult with someone who does, and not post questions on line. Clearly, you are out of your area of experience, so you must access that experience locally. We cannot provide step by step help to people in the open forums, because they are indexed by search engines.

    Article 440 is well explained in a youtube video by Mike Holt. He will tell you the same things that I have.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist
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  5. #18
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    Quote Originally Posted by RR449A View Post
    If MCC is the current under which the thermal Protection activates, what use do we have from breaker?

    Aren't the limits defined by envelope?
    The operating envelope defines the limits of normal operation as determined by the compressor manufacturer.

    The compressor's thermal/overload protection is designed to protect the motor from over-current and high internal temperatures.

    The circuit breaker or fuse is for over-current and short circuit protection.

  6. #19
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    I just caught that you are installing Bitzer equipment.

    They have all of the answers you need.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

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  7. #20
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    There is a difference in "overload protection" and "overcurrent protection" despite it being somewhat common for folks to use them interchangeably.

    There are a lot of things needed to be fully understood before trying to design electrical and mechanical systems to work together.

    One example, if your name plate says Max Fuse Size, you are required to use fuse protection not breakers it's not just an amp rating, it is indeed specific to using fuses only.

  8. #21
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    Thread Starter
    Quote Originally Posted by timebuilder View Post
    Have your men size the co0nductors and the protection according to what I explained. Any good electrician will know what to do.

    If you do not know which table to use in the NEC, you must consult with someone who does, and not post questions on line. Clearly, you are out of your area of experience, so you must access that experience locally. We cannot provide step by step help to people in the open forums, because they are indexed by search engines.
    I have electrician size wires etc., I am not worried about that, and you are right, I am out of my area of experience, but I like to Know how and what is being done.

  9. #22
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    Quote Originally Posted by icemeister View Post
    The circuit breaker or fuse is for over-current and short circuit protection.
    Quote Originally Posted by idontgetit View Post
    One example, if your name plate says Max Fuse Size, you are required to use fuse protection not breakers it's not just an amp rating, it is indeed specific to using fuses only.
    I use electrical panels which have fuse and adjustable motor protector (breaker), like this one:

    https://assets.danfoss.com/documents...3286434757.pdf

    For fuse I am not worried. I am worried for compressor, i.e. adjustable motor protector. I really don't understand why should the motor protector (breaker) be adjusted according to MCC which is outside anvelope.

  10. #23
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    In that case...once again, you need to contact the manufacturer.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

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  11. #24
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    Quote Originally Posted by RR449A View Post
    For fuse I am not worried. I am worried for compressor, i.e. adjustable motor protector. I really don't understand why should the motor protector (breaker) be adjusted according to MCC which is outside anvelope.
    As I explained earlier, the envelope defines the limits of normal operation. Conditions outside these limits are considered as potentially damaging and/or unsafe, so protective devices are required to prevent operation outside of the envelope. Such devices would be the high and low pressure controls. The manufacturer's recommended settings for these controls are directly related to the operating envelope's limits, and would typically be set just outside these limits (since settings inside the operating envelope would make no sense).

    The compressor's thermal protection for example, isn't directly related to the operating envelope, rather its settings are determined by the motor manufacturer's limits for the motor winding temperature. It's possible for these limits to be exceeded even while the compressor is running within its operating envelope due to some fault in the compressor or system.

  12. #25
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    Quote Originally Posted by RR449A View Post
    I use electrical panels which have fuse and adjustable motor protector (breaker), like this one:

    https://assets.danfoss.com/documents...3286434757.pdf

    For fuse I am not worried. I am worried for compressor, i.e. adjustable motor protector. I really don't understand why should the motor protector (breaker) be adjusted according to MCC which is outside anvelope.
    That appears to be an electronically-controlled motor protection device.

    It is not a "breaker."
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

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  13. #26
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    Again, revert back to the manufacturer
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