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Thread: Series Rated panel

  1. #1
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    Series Rated panel

    I have a project where I need to install a transformer and a panel. The panel which feeds the transformer is a series rated panel. My question is the new panel which is fed from the new transformer does it have to be series rated? Can this panel be fully rated?

  2. #2
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    I don't see any reason it couldn't be either.

    What's on the primary side of the transformer doesn't have any effect on the ratings on the secondary side of the transformer.

    And in general, having a series rated panel doesn't have any effect on what is installed downstream (as long as everything downstream is rated for the available fault current at its downstream location).

  3. #3
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    Curious, what size transformer ?
    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.

  4. #4
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    Quote Originally Posted by Rai136926 View Post
    I have a project where I need to install a transformer and a panel. The panel which feeds the transformer is a series rated panel. My question is the new panel which is fed from the new transformer does it have to be series rated? Can this panel be fully rated?
    You never have to series rate panels. it is a option to reduce equipment costs.
    You can always fully rate.

  5. #5
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    Quote Originally Posted by Sierrasparky View Post
    You never have to series rate panels. it is a option to reduce equipment costs.
    You can always fully rate.
    That's what I meant, but you said it much better.

  6. #6
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    Ther transform size is 75KVA 480-208/120V.

  7. #7
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    Quote Originally Posted by Rai136926 View Post
    Ther transform size is 75KVA 480-208/120V.
    It is extremely unlikely that you will need to worry about the AIC rating for any OCPD's on the load side of that transformer, even without any series rating. You should be well under 10k.
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

  8. #8
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    Quote Originally Posted by Rai136926 View Post
    I have a project where I need to install a transformer and a panel. The panel which feeds the transformer is a series rated panel. My question is the new panel which is fed from the new transformer does it have to be series rated? Can this panel be fully rated?
    Series rating means the downstream/branch breakers can take credit for the KAIC rating of the upstream/main breakers/other OCPD, even though the downstream/branch devices have a lower KAIC rating. This way your branch breakers and subpanels can have lower ratings (thus cheaper equipment), while your devices closest to the source carry the full rating and interrupt the fault before it gets to the downstream devices. Series ratings apply to a combination of two OCPDs that are tested together to make sure the higher rated device coordinates to trip before the downstream device catastrophically fails.

    Typically, a product family of breakers, will be series rated with a certain fuse class. An example is Square D's QOB breakers with 10 KAIC series rated with Class J fuses at 200 KA. The panelboard with QOB breakers can therefore be anywhere downstream of the disconnect fused with Class J fuses, and the system is capable of up to 200 kA of fault current. Another example you might see, is one breaker product family series rated with another breaker family, within the same manufacturer. Few (if any) series rated combinations will mix breaker manufacturers.

  9. #9
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    You would need the specifics on your particular transformer. According to the charts on this site
    http://www1.cooperbussmann.com/libra...pr_booklet.pdf you may be looking at 23k +/- . (see Chart Pg 9)
    That's high enough to warrant your investigating the transformer (impedance) and calculating your particular situation. If you are 22k or less, a series rated panel in commonly available.
    Last edited by augie47; 11-16-17 at 08:04 AM.
    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.

  10. #10
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    Quote Originally Posted by augie47 View Post
    You would need the specifics on your particular transformer. According to the charts on this site
    http://www1.cooperbussmann.com/libra...pr_booklet.pdf you may be looking at 23k +/- . (see Chart Pg 9)
    That's high enough to warrant your investigating the transformer (impedance) and calculating your particular situation. If you are 22k or less, a series rated panel in commonly available.

    A typical 75 kva 480 to 120/208 has an impedance between 3.5 and 5.5 - at least every one that I have seen. I am not saying there are zero exceptions, but very likely AIC not an issue. Agree though, always check transformer.
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

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