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Thread: NEC 427.22, GFP 300mA

  1. #1
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    NEC 427.22, GFP 300mA

    I have an application that falls under NEC427.22, electric heat tracing of pipelines and vessels. 10 branch circuits fed out of an enclosure each have thermal magnetic breaker and GFP 30mA. The problem is that some of the circuits are tripping. Installation has been checked. The GFP breakers are available in 300mA sensitivity and I am considering replacing the 30mA protectors with 300mA. Per NEC427.22, the protector 'is sensitive to leakage currents in the magnitude of 6mA to 50mA'. Does the 300mA GFP comply with 427.22, if not what is the 300mA sensitivity unit used for? Thank you.

  2. #2
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    Welcome to the forum.

    To comply with 427.22 you would need to use GFPE which as you stated has a trip range of 30 to 50 milliamps.

    I don't believe that the 300 milliamp device would be listed as GFPE protection but as just GFP protection.

    Chris

  3. #3
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    Does the NEC address the use of 300mA ground fault protectors? If not, who does? Thank You.

  4. #4
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    I don't believe that the code specifies the trip point for the ground fault protection that is required by 427.22. The defintion leaves the trip point issue open.
    Don, Illinois
    "It is the first responsibility of every citizen to question authority." B Franklin

  5. #5
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    I do expect that there is some issue with the installation and or the heat trace itself. The manufacturers are aware of the code rule and also know that in most cases this protection is provided by a device with a 30 to 50 mA trip point. The installation should not be tripping the ground fault protection device.
    What steps were taken when the system was "checked out" to prove that the leakage current is within the normal range?
    Don, Illinois
    "It is the first responsibility of every citizen to question authority." B Franklin

  6. #6
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    Quote Originally Posted by don_resqcapt19 View Post
    I don't believe that the code specifies the trip point for the ground fault protection that is required by 427.22. The defintion leaves the trip point issue open.
    Don, 427.22 requires ground fault protection of equipment.

    According to the UL White Book, the trip threshold for Equipment Ground-fault Protective Devices (FTTE) is limited to the range above 6 mA to 50 mA.

    It also states that EGFPDs are intended for use in applications where ground-fault protection of equipment is required by the National Electrical Code, specifically Sections 426-28 and 427-22, or where such protection is deemed appropriate.

    Chris

  7. #7
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    Quote Originally Posted by raider1 View Post
    Don, 427.22 requires ground fault protection of equipment.

    According to the UL White Book, the trip threshold for Equipment Ground-fault Protective Devices (FTTE) is limited to the range above 6 mA to 50 mA.

    It also states that EGFPDs are intended for use in applications where ground-fault protection of equipment is required by the National Electrical Code, specifically Sections 426-28 and 427-22, or where such protection is deemed appropriate.

    Chris
    That is a good point, but the NEC definition of what ground fault protection of equipment is does not spell that out. Just because UL say that those listed devices are suitable for compliance with 427.22 does not mean other devices are not suitable. If the NEC intends to require a specific trip point, it should be spelled out in the definitions like it is for GFCIs. While the handbook commentary spells out a trip range nothing in code itself does.
    Don, Illinois
    "It is the first responsibility of every citizen to question authority." B Franklin

  8. #8
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    Quote Originally Posted by BSEET1986 View Post
    I have an application that falls under NEC427.22, electric heat tracing of pipelines and vessels. 10 branch circuits fed out of an enclosure each have thermal magnetic breaker and GFP 30mA. The problem is that some of the circuits are tripping. Installation has been checked. The GFP breakers are available in 300mA sensitivity and I am considering replacing the 30mA protectors with 300mA. Per NEC427.22, the protector 'is sensitive to leakage currents in the magnitude of 6mA to 50mA'. Does the 300mA GFP comply with 427.22, if not what is the 300mA sensitivity unit used for? Thank you.
    are the circuits multi-wired? (sharing the neutral) multi-wired circuits with GFPE that do not have double pole breakers with the GFPE then you will have problems like this. also a grounded neutral will cause them to trip after the load is applied.
    Wayne A. From: N.W.Indiana
    Be Fair, Be Safe
    Just don't be fairly safe

  9. #9
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    Thanks for the replies. I am checking the installation. For future, I thought I would use 300mA GFEP for all applcations but code requires 6 to 50mA. So, manufacturers offer 300mA GFEP but not GFEP code compliant. If anyone has used a 300mA GFEP, where was it used? Any info or code references would be helpful.

  10. #10
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    Quote Originally Posted by don_resqcapt19 View Post
    That is a good point, but the NEC definition of what ground fault protection of equipment is does not spell that out. Just because UL say that those listed devices are suitable for compliance with 427.22 does not mean other devices are not suitable. If the NEC intends to require a specific trip point, it should be spelled out in the definitions like it is for GFCIs. While the handbook commentary spells out a trip range nothing in code itself does.
    I see your point. The NEC definition does not specifically give us the 6-50 milliamp threshold requirement for GFPE.

    Chris

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