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Thread: Fire Pump Service & Utility Company Responsibilities?

  1. #11
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    Found some additional info specifically on transformers while researching another issue (NFPA 70-2014 695.5(B)):

    (B) Overcurrent Protection. The primary overcurrent pro-
    tective device(s) shall be selected or set to carry indefitely
    the sum of the locked-rotor current
    of the fire pump motor(s)
    and the pressure maintenance pump motor(s) and the full-load
    current of the associated fire pump accessory equipment when
    connected to this power supply. Secondary overcurrent protec-
    tion shall not be permitted. The requirement to carry the
    locked-rotor currents indefinitely shall not apply to conductors
    or devices other than overcurrent devices in the fire pump
    motor circuit(s).

    So yeah, the transformer needs to be fused at not less than 35 amps on the primary side. Note that no protection is allowed on the secondary side.

  2. #12
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    Quote Originally Posted by gadfly56 View Post
    Found some additional info specifically on transformers while researching another issue (NFPA 70-2014 695.5(B)):

    (B) Overcurrent Protection. The primary overcurrent pro-
    tective device(s) shall be selected or set to carry indefitely
    the sum of the locked-rotor current
    of the fire pump motor(s)
    and the pressure maintenance pump motor(s) and the full-load
    current of the associated fire pump accessory equipment when
    connected to this power supply. Secondary overcurrent protec-
    tion shall not be permitted. The requirement to carry the
    locked-rotor currents indefinitely shall not apply to conductors
    or devices other than overcurrent devices in the fire pump
    motor circuit(s).

    So yeah, the transformer needs to be fused at not less than 35 amps on the primary side. Note that no protection is allowed on the secondary side.
    But 695.5 would not apply to a utility transformer. It's for a transformer owned by the customer. Notice where it says "where the supply voltage is different than the fire pump voltage' or something similar.

    I still think you have it right. I just don't think its covered in this paragraph.

  3. #13
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    Quote Originally Posted by steve66 View Post
    But 695.5 would not apply to a utility transformer. It's for a transformer owned by the customer. Notice where it says "where the supply voltage is different than the fire pump voltage' or something similar.

    I still think you have it right. I just don't think its covered in this paragraph.
    695 doesn't care who owns the transformer, it still has to meet the requirements. The POCO isn't bound by it but the customer is. Now, if you're trying to provide what your customer wants then you should pay attention to the to the NEC in this case.

  4. #14
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    Quote Originally Posted by ActionDave View Post
    Welcome to the forum.

    The NEC does not cover power company equipment. Basically the NEC starts where the power company ends and that is called the Service Point.
    On the one (100 hp) electric fire pump I work on, there is a note on the one line about the fuse size for the primary.
    so maybe our POCO has some engineering notes or standard to coordinate with the customer
    Moderator-Washington State
    Ancora Imparo

  5. #15
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    Quote Originally Posted by gadfly56 View Post
    695 doesn't care who owns the transformer, it still has to meet the requirements. The POCO isn't bound by it but the customer is. Now, if you're trying to provide what your customer wants then you should pay attention to the to the NEC in this case.

    Read the first sentence again: "Where the service or system voltage is different from the utilization voltage of the fire pump motor....."

    This only applies to transformers after the service connection point.

    All electric services are supplied by a utility transformer, so if this section applied to utility transformers, there could never be any overcurrent protection on a fire pump service. That would make 695.4B a total waste of ink.

  6. #16
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    Quote Originally Posted by steve66 View Post
    Read the first sentence again: "Where the service or system voltage is different from the utilization voltage of the fire pump motor....."

    This only applies to transformers after the service connection point.

    All electric services are supplied by a utility transformer, so if this section applied to utility transformers, there could never be any overcurrent protection on a fire pump service. That would make 695.4B a total waste of ink.
    I don't see how you can say that. If the distribution voltage from the POCO is 19K and they drop a transformer that supplies my facility with 460 which is also what my fire pump runs at that POCO transformer has to supply the locked rotor current for my fire pump(s).

  7. #17
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    Quote Originally Posted by gadfly56 View Post
    I don't see how you can say that. If the distribution voltage from the POCO is 19K and they drop a transformer that supplies my facility with 460 which is also what my fire pump runs at that POCO transformer has to supply the locked rotor current for my fire pump(s).
    I have to agree with you..In NEC section 695.5 it says that

    Transformers. Where the service or system voltage
    is different from the utilization voltage of the fire pump
    motor, transformer(s) protected by disconnecting means
    and overcurrent protective devices shall be permitted to be
    installed between the system supply and the fire pump controller
    in accordance with 695.5(A) and (B).

    So even if the utility supply voltage is different from the firepump controller voltage you have to size them based on 695.5(B) where it clearly states that the "The primary overcurrent protective
    device(s) shall be selected or set to carry indefinitely the sum of the locked rotor current of the fire pump motors and the pressure maintenance pmp motors and full current associated fire pump accessory equipment when connected to this power supply"

  8. #18
    Join Date
    May 2006
    Posts
    407
    Guys,

    I think you have drifted to far back in your book. Section 90.2(B)(5) places installations under the exclusive control of a utility outside the scope of the code, so you can stop reading right there. The customer may need to install an alternate source of power but the AHJ has no say in the protection of a utility transformer.

    RB

  9. #19
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    Quote Originally Posted by gadfly56 View Post
    I don't see how you can say that. If the distribution voltage from the POCO is 19K and they drop a transformer that supplies my facility with 460 which is also what my fire pump runs at that POCO transformer has to supply the locked rotor current for my fire pump(s).
    I'm paraphrasing here, but the first sentence basically says "Where the service voltage is different than the fire pump voltage a transformer shall be permitted between the system supply and the fire pump controller."

    So this only applies when the source voltage is different than the fire pump voltage. Note that "source" or "service" refers back to the sources listed in 695.3, so the source or service is the "Electric Utility Service Connection". As a result, 695.5 only applies for a customer owned transformer after the service, or a transformer connected to a generator or an on site power production facility.


    Again, I still agree with you that the utility primary fusing should carry the locked rotor current, or an alternate source must be provided, but that's just not the right paragraph to quote.

    I do not agree with this:

    Quote Originally Posted by gadfly56 View Post
    Note that no protection is allowed on the secondary side.
    And overcurrent protection is permitted on the secondary side of a utility transformer that supplies a fire pump, just not on the secondary of a privately owned transformer.

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