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Chiller Feeder Calculation

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  • david luchini
    replied
    Originally posted by mull982 View Post
    Ok I was finally able to track down the datasheets for these chillers. Chiller rated capacity is 348 (assuming tons) with 205kW at rated 100% load.

    The datasheet gives the following: Compressor RLA = 124/158A, MCA=321A, MOP=450A. (3) identical chillers with these values.

    I'm not quite sure what the RLA would be provided with (2) different values? These would lead to two very different feeder calcs.
    The chiller has two compressors. One with 124A RLA, one with 158A RLA.

    Originally posted by mull982 View Post
    New Feeder Calc using 124A RLA will be: 321A + 124A + 124A = 569A

    New Feeder Calc using 158A RLA will be: 321A + 158A + 158A = 637A

    Am I looking at these feeder calcs right based off of this new information? Which RLA value to use will have a pretty significant impact in that it will determine weather we are over/under the 600A threshold which will have impact on breaker rating, ATS rating, etc......

    Thanks for the help!
    321A+282A+282A=885A

    Leave a comment:


  • mull982
    replied
    Ok I was finally able to track down the datasheets for these chillers. Chiller rated capacity is 348 (assuming tons) with 205kW at rated 100% load.

    The datasheet gives the following: Compressor RLA = 124/158A, MCA=321A, MOP=450A. (3) identical chillers with these values.

    I'm not quite sure what the RLA would be provided with (2) different values? These would lead to two very different feeder calcs.

    New Feeder Calc using 124A RLA will be: 321A + 124A + 124A = 569A

    New Feeder Calc using 158A RLA will be: 321A + 158A + 158A = 637A

    Am I looking at these feeder calcs right based off of this new information? Which RLA value to use will have a pretty significant impact in that it will determine weather we are over/under the 600A threshold which will have impact on breaker rating, ATS rating, etc......

    Thanks for the help!

    Leave a comment:


  • kwired
    replied
    Originally posted by Sahib View Post
    NEC requirements for air conditioners (other than room air conditioners) and chillers are same. So the article about air conditioners is also about chillers.
    Mostly yes, if there is hermetic compressors involved art 440 usually applies.

    Leave a comment:


  • Sahib
    replied
    Originally posted by david luchini View Post
    It doesn't mention "chillers" anywhere in the article. Where would you find a chilled water chiller?
    NEC requirements for air conditioners (other than room air conditioners) and chillers are same. So the article about air conditioners is also about chillers.

    Originally posted by david luchini View Post

    They would test a product to UL standards, not to what this article says.
    The calculations in the article are based on UL standard. ( Post#31).

    Leave a comment:


  • retirede
    replied
    Originally posted by david luchini View Post
    It distinguishes between motor operated equipment with a heretic refrigerant motor-compressor and equipment without.
    Those heretic types are the worst. [emoji3]

    They’re always in trouble with the Pope!

    Leave a comment:


  • steve66
    replied
    UL 1995 36.14 seems to be the US standard for determining equipment MCA:

    Minimum Circuit Ampacity
    36.14 The minimum circuit ampacity (MCA) required by Clause 36.3(h) shall be determined as follows. All
    concurrent load conditions are to be considered in the determinations, see Figure 36.1. Whichever load
    condition provides the highest value shall be used.
    a) For a motor group only, a load consisting of two or more motors, the rated current of the largest
    motor or branch circuit selection current, if marked, (see Clauses 36.11 and 36.12), multiplied by 125
    per cent, added to the rated currents of all of the other motors.
    b) For a combination load, a load consisting of one or more motors, electric heaters, and any other
    loads, that incorporates one or more compressor motors, the rated current of the largest motor
    compressor or branch circuit selection current, if marked, (see Clauses 36.11 and 36.12), multiplied by
    125 per cent, added to which shall be the value obtained by multiplying the rated current of the electric
    heaters by 125 per cent, and adding to that total the sum of the ratings of all other loads.
    c) For a combination load, a load consisting of one or more motors, electric heaters, and any other
    loads, not involving a hermetic refrigerant motor compressor, the sum of the rated currents multiplied by
    125 per cent.
    Exception: The rated current of the heater load may be multiplied by 100 percent, rather than 125 per cent,
    provided that
    1) the rated heater load at a field wiring terminal is 50 kW or more;
    2) the minimum conductor size that may be field-connected to such terminal is still to be marked;
    and
    3) the heater element circuits connected to the field wiring terminals are subdivided as specified in
    Clause 30.8 and are arranged to be controlled by one or more temperature-actuated devices to
    reduce the likelihood of continuous simultaneous operation of all of the element circuits.


    Also, it looks like nameplate motor currents aren't always used to calculate MCA;

    https://www.titus-hvac.com/softwares...ecalculate.pdf

    Leave a comment:


  • david luchini
    replied
    Originally posted by Sahib View Post
    Sorry, it is not clear how the article is not applicable to ''chillers''.
    It doesn't mention "chillers" anywhere in the article. Where would you find a chilled water chiller?

    Originally posted by Sahib View Post
    UL or other third party certifying agency would test such a product design anyway for any danger to life and property. There would be none.......
    They would test a product to UL standards, not to what this article says.

    Leave a comment:


  • Sahib
    replied
    Originally posted by david luchini View Post
    No (except for the special provisions for room air-conditioners.) It distinguishes between motor operated equipment with a heretic refrigerant motor-compressor and equipment without.
    Sorry, it is not clear how the article is not applicable to ''chillers''.

    Originally posted by david luchini View Post
    Nobody would pass a product design based on this article. It's just an article, and not a very good one.
    UL or other third party certifying agency would test such a product design anyway for any danger to life and property. There would be none.......

    Leave a comment:


  • david luchini
    replied
    Originally posted by Sahib View Post
    Thanks for your response. I wonder whether i)NEC distinguishes between air conditioner and chiller
    No (except for the special provisions for room air-conditioners.) It distinguishes between motor operated equipment with a heretic refrigerant motor-compressor and equipment without.

    Originally posted by Sahib View Post
    and ii)UL or third party certifying authority would pass a product design also based on this article
    Nobody would pass a product design based on this article. It's just an article, and not a very good one.

    Leave a comment:


  • Sahib
    replied
    Originally posted by david luchini View Post
    The original question was about Chillers. The article you linked is about Air Conditioners.




    No it's not. The NEC tells you how to calculate MCA and MOCP. The article you linked doesn't follow the NEC requirements.
    Thanks for your response. I wonder whether i)NEC distinguishes between air conditioner and chiller and ii)UL or third party certifying authority would pass a product design also based on this article and so the AHJ because there is no violation of intent of NEC ie there is no danger to life and property.

    Leave a comment:


  • david luchini
    replied
    Originally posted by Sahib View Post
    Please clarify, if possible.
    The original question was about Chillers. The article you linked is about Air Conditioners.


    Originally posted by Sahib View Post
    That is AHJ's call.
    No it's not. The NEC tells you how to calculate MCA and MOCP. The article you linked doesn't follow the NEC requirements.

    Leave a comment:


  • Sahib
    replied
    Originally posted by david luchini View Post
    The article isn't relevant to Chillers.
    Please clarify, if possible.
    Originally posted by David luchini View Post
    Nor does it completely follow the NEC.
    That is AHJ's call.

    Leave a comment:


  • david luchini
    replied
    Originally posted by Sahib View Post
    I do not believe the article in my last post is against the intent of NEC or is not on topic.
    The article isn't relevant to Chillers. Nor does it completely follow the NEC.

    Leave a comment:


  • Sahib
    replied
    Originally posted by electrofelon View Post
    Please try to stay on topic. The OP was about the NEC load calculation, so it doesn't matter what you think is overkill or what might/should be or if the compressor has polka dots on it.
    I do not believe the article in my last post is against the intent of NEC or is not on topic.

    Leave a comment:


  • electrofelon
    replied
    Originally posted by Sahib View Post
    Please try to stay on topic. The OP was about the NEC load calculation, so it doesn't matter what you think is overkill or what might/should be or if the compressor has polka dots on it.

    Leave a comment:

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