Electrical Isolator > What Does The M Rating Represent?

DoctorCalculon on 04/04/2024 - 19:06

This question is mainly for the OzSparkies that are lurking around who paid attention during all the boring lectures.

Lets compare the following two electrical isolators:

NHP 2P 20A Weatherproof Isolating Switch <- M120 Rating

vs

NHP 2P 40A Weatherproof Isolating Switch <- M180 Rating

I am aware that the 2P represents 2 poles, i.e. the isolator can isolate two different circuits using the same switch.
(20|40)A is the max input current.

What I want to know is what does the M rating / attribute represent?

Yes, I did a basic google before posting this thread. However, my google-fu must be very weak at the moment.

Thank you in advance for any helpful pointers.

Electrical & Electronics

Comments

  • Master Bates on 04/04/2024 - 19:19
    +2

    Not a Sparky, but used my Google-fu… and happy to be corrected by a professional.

    It appears to be a Motor Rating, for the maximum VA motor it can isolate.

    E.g. “The IPW series is tested to the requirements of AS3133 providing a “M” or motor rating allowing the direct control of motors.” - Source

  • SBOB on 04/04/2024 - 20:05

    https://updates.clipsal.com/clipsalonline/Files/Brochures/I0…
    M-Rating (refer AS/NZS3133)
    Clipsal switches and switched socket outlets are marked with an M-Rating. This indicates that these products have
    been tested and found suitable for switching locked rotor current.
    In part, this test involves 50 operations, make and break of the nominated locked rotor current at 0.5 power factor
    lagging. The switch will not fail to interrupt the current or fail in any way electrically or mechanically

    eg unless you're switching something like a DOL motor with an in-rush current, dont worry about it :)

    • DoctorCalculon on 04/04/2024 - 22:44

      eg unless you're switching something like a DOL motor with an in-rush current, dont worry about it :)

      The application is not for DOL motors or pool pumps, which are obviously high inductive load.

      Mainly for aircon outdoor units, and the most recent application will be for the heat pump unit of a Reclaim Energy HP HWS.

    • DoctorCalculon on 04/04/2024 - 23:00

      In part, this test involves 50 operations, make and break of the nominated locked rotor current at 0.5 power factor
      lagging. The switch will not fail to interrupt the current or fail in any way electrically or mechanically

      But what is the scale for this unit? Is it logarithmic or linear?

      When I google AS/NZS3133, most of the articles are dealing with air-break switches.

      dont worry about it

      I just want to fully understand this attribute from an academic point of view.

  • Tricon on 05/04/2024 - 16:23
    +1

    Perhaps you can call or email NHP with your query. Pre-sales support from such organisations is typically very good.

    • DoctorCalculon on 05/04/2024 - 20:28

      Funny that you mention this.
      I had contacted Clipsal as it is the most popular and trusted brand.
      No, they couldn't answer the question. Once I receive a call back from their technical team with the answer, I will post it here.

      • Tricon on 05/04/2024 - 21:01
        +1

        I would suggest contacting NHP or IPD rather than Clipsal as they are better related to engineering companies rather than the Clipsal box sellers.

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