501.34- Bonding jumper required in Class I area?

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greenspark1

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New England
Hi. I'm a bit confused about what NEC 501.34 requires. I am running a 3" conduit with equipment ground to a motor in a class I location. At the motor I am connecting with liquidtight conduit the last 3'. Ground fault current would be carried back to the panel by the EGC. 501.34 seems to say that due to the liquidtight conduit I need to install a bonding jumper to ensure the conduit stays grounded. Am I reading that right? I'm going to need a lot of jumpers since most of my hazardous conduit runs have flex in them somewhere.

Also, 501.34(A) seems to say that since I am coming from a class I area, where my RMC enters my panelboard I need additional bonding above a standard locknut. True?

Any comments/explanation is appreciated!
 
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Gregg Harris

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greenspark1 said:
Hi. I'm a bit confused about what NEC 501.34 requires. I am running a 3" conduit with equipment ground to a motor in a class I location. At the motor I am connecting with liquidtight conduit the last 3'. Ground fault current would be carried back to the panel by the EGC. 501.34 seems to say that due to the liquidtight conduit I need to install a bonding jumper to ensure the conduit stays grounded. Am I reading that right? I'm going to need a lot of jumpers since most of my hazardous conduit runs have flex in them somewhere.

Also, 501.34(A) seems to say that since I am coming from a class I area, where my RMC enters my panelboard I need additional bonding above a standard locknut. True?

Any comments/explanation is appreciated!
Click to expand...

Take a look at exception if your liquidtite is 6 feet or less and fittings listed for grounding.
 
don_resqcapt19

don_resqcapt19

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The flex needs a bonding jumper and you need "service type" bonding on the raceways back to the location of the system or main bonding jumper.
 
rbalex

rbalex

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greenspark1 said:
Thanks Don. Can you help me understand why the flex needs a bonding jumper if there is an equipment ground run within?
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First notice that the grounding/bonding requirements are the same for every Class and Division or Zone including nonincendive and intrinsically safe wiring methods.

Code Making Panel 14 is paranoid about possible circulating ground currents and is of the opinion that an arc could occur in the turns of interlocked armor or at the interfaces of double-locknut or locknut-bushing type bonds.
 
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greenspark1

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Location
New England
rbalex said:
First notice that the grounding/bonding requirements are the same for every Class and Division or Zone including nonincendive and intrinsically safe wiring methods.

Code Making Panel 14 is paranoid about possible circulating ground currents and is of the opinion that an arc could occur in the turns of interlocked armor or at the interfaces of double-locknut or locknut-bushing type bonds.
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Wow, wild/weird, thanks :)
So can you point out which section is requiring this? I believe I meet 501.32(B) since I DO have a separate ground fault current path (the EGC).
 
rbalex

rbalex

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Would you mind telling us what NEC Edition you are citing? Every Edition since 2008 has Grounding/Bonding under 501.30 and the basic rules have been the same long before that. Double-locknut and locknut-bushing bonds have been prohibited as long as I've been in the business. They may have been word-smithed a bit since the mid-nineties, but the restrictions for LMFT have been pretty much the same since then too.

Remember the NEC isn't necessarily committed to explaining "why" something is a requirement. [Section 90.1(C)]
 
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greenspark1

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Location
New England
rbalex said:
Would you mind telling us what NEC Edition you are citing? Every Edition since 2008 has Grounding/Bonding under 501.30 and the basic rules have been the same long before that. Double-locknut and locknut-bushing bonds have been prohibited as long as I've been in the business. They may have been word-smithed a bit since the mid-nineties, but the restrictions for LMFT have been pretty much the same since then too.

Remember the NEC isn't necessarily committed to explaining "why" something is a requirement. [Section 90.1(C)]
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Sorry that was my typo. Yes I'm looking at 501.30 in the 2008 edition.

So, 501.30 (A) says that locknut and double locknut type shall not be depended on for bonding purposes. What about wrench-tight connections? I read this section to mean that all metal conduit, whether liquidtight flex or not, needs bonding bushings or jumpers at all couplings and devices in hazardous areas?
 
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Gregg Harris

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greenspark1 said:
Sorry that was my typo. Yes I'm looking at 501.30 in the 2008 edition.

So, 501.30 (A) says that locknut and double locknut type shall not be depended on for bonding purposes. What about wrench-tight connections? I read this section to mean that all metal conduit, whether liquidtight flex or not, needs bonding bushings or jumpers at all couplings and devices in hazardous areas?
Click to expand...

Drop back to 250.100 and it will send you to 250.92(B)(2) through (B)(4)
 
rbalex

rbalex

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greenspark1 said:
Yes, I read 250.100 which refers to 250.92, which only talks about services. The situation I am asking about is a feeder out to a motor.
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As Don stated in Post #4, you are required to use "service type" bonding in classified locations.

greenspark1 said:
So, 501.30 (A) says that locknut and double locknut type shall not be depended on for bonding purposes. What about wrench-tight connections? I read this section to mean that all metal conduit, whether liquidtight flex or not, needs bonding bushings or jumpers at all couplings and devices in hazardous areas?
Click to expand...
Couplings and threaded devices already use a recognized "service type" bond. That's why locknut-bushing and double-locknuts had to be specifically prohibited since they are threaded too; however, wrench tight or not, they don't guarantee five full threads of engagement. [Section 500.8(E), 2008 NEC] Note, while 500.9(E) references explosionproof equipment all Article 501-506 Grounding/Bonding Sections, makes no significant distinction between Class and Division or Zones with regard to grounding/bonding requirements. CMP14 wants threaded connections or recognized bonding jumpers in classified locations.

Articles 500-516 have always been strong applications of Section 90.1(C). The last few years of "wordsmithing", especially Section 501.30(B) and its counterparts in Articles 502-506, hasn't helped. I'm something of a contrarian. I believe some of the more draconian requirements should be limited To Class I, Division 1 and Class II, Group E and their counterparts in Articles 505 and 506. But efforts to achieve that have been routinely rejected. I gave up years ago.
 
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