Bonding

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Big Guns

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Hello fellow electricians

I just had a generator room fail an inspection for the following reason, I have PVC conduit coming from the slab, I transitioned over to rigid the to seal tite into the generator, the seal tite was less than 6 feet long, the inspector said I have to have an external bond. Why and what artical states this. I also have a ground wire ran with the feeders in the seal tite
 
Check 250.118(6).
In all probability your OCP exceeds limit of the LFMC grounding capability.
 
Big Guns said:
Hello fellow electricians

I just had a generator room fail an inspection for the following reason, I have PVC conduit coming from the slab, I transitioned over to rigid the to seal tite into the generator, the seal tite was less than 6 feet long, the inspector said I have to have an external bond. Why and what artical states this. I also have a ground wire ran with the feeders in the seal tite
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I always install a grounding bushing on any genset or transformer its a fine line with inspectors some dont look some do but if your generator is a big one it kinda pays for the time to do it twice .

They think the short flex will become unprotected by vibration over time by the connection to the metal case of the generator so if ya ground it your done .

I always ground it code or no code .
 
ohmhead said:
I always install a grounding bushing on any genset or transformer its a fine line with inspectors some dont look some do but if your generator is a big one it kinda pays for the time to do it twice .

They think the short flex will become unprotected by vibration over time by the connection to the metal case of the generator so if ya ground it your done .

I always ground it code or no code .
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In this case a bonding bushing would not solve the problem. The short section of rigid conduit would still rely on the LFMC to provide a bonding path which, unless it's a very small size, it wouldn't comply with the NEC. They do make LFMC connectors with bonding hubs on them. Here's the relevant code section:

250.118Types of Equipment Grounding Conductors.
(6) Listed liquidtight flexible metal conduit meeting all the following conditions:
a. The conduit is terminated in listed fittings.
b. For metric designators 12 through 16 (trade sizes through ?), the circuit conductors contained in the conduit are protected by overcurrent devices rated at 20 amperes or less.
c. For metric designators 21 through 35 (trade sizes ? through 1?), the circuit conductors contained in the conduit are protected by overcurrent devices rated not more than 60 amperes and there is no flexible metal conduit, flexible metallic tubing, or liquidtight flexible metal conduit in trade sizes metric designators 12 through 16 (trade sizes through ?) in the grounding path.
d. The combined length of flexible metal conduit and flexible metallic tubing and liquidtight flexible metal conduit in the same ground return path does not exceed 1.8 m (6 ft).
e. Where used to connect equipment where flexibility is necessary after installation, an equipment grounding conductor shall be installed.
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glene77is said:
Big,

What size is the "ground wire ran with the feeders" ?
I assume this ground is run inside the LFMC,
like 3 hots, neutral,and EGC green.
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Since he's looking to bond a short section of metallic raceway why would that matter?
 
infinity said:
Since he's looking to bond a short section of metallic raceway why would that matter?
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Infinity,

" PVC conduit coming from the slab "
I was thinking that this incoming conduit was a long (undefined) length.
I got the idea that his incoming EGC was not large enough,
so I was fishing for some more info.
 
glene77is said:
Infinity,

" PVC conduit coming from the slab "
I was thinking that this incoming conduit was a long (undefined) length.
I got the idea that his incoming EGC was not large enough,
so I was fishing for some more info.
Click to expand...

Got it. He did say that he has " a ground wire ran with the feeders in the seal tite " so maybe I was reading something into it.
 
Is it required to have a second ground conductor ( externally on the conduit ) that matches the EGC run in the conduit? The LMFC needs to be bonded but it is not the EGC.
This may sound silly but, if the LMFC is only rated to carry a 60 amp ground, and you run a 1/0 external to the RGS, don't you still need to up the grounding capacity of the LMFC to that of the RGS ? wouldn't the EGC was run inside the conduit cover the grounding requirements and the rest just be a bond to the LMFC?
 
acrwc10 said:
Is it required to have a second ground conductor ( externally on the conduit ) that matches the EGC run in the conduit? The LMFC needs to be bonded but it is not the EGC.
This may sound silly but, if the LMFC is only rated to carry a 60 amp ground, and you run a 1/0 external to the RGS, don't you still need to up the grounding capacity of the LMFC to that of the RGS ? wouldn't the EGC was run inside the conduit cover the grounding requirements and the rest just be a bond to the LMFC?
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There is no bonding path for the RGS that would meet the requirement of code if the circuit conductors are over 60 amps, the EGC inside of the conduit does not bone the RGS, the LMFC does not bond the RGS over 60 amp circuit conductors, so the only thing code compliant would be an external EGC under 6' to a clamp on the RGS.
 
hurk27 said:
There is no bonding path for the RGS that would meet the requirement of code if the circuit conductors are over 60 amps, the EGC inside of the conduit does not bone the RGS, the LMFC does not bond the RGS over 60 amp circuit conductors, so the only thing code compliant would be an external EGC under 6' to a clamp on the RGS.
Click to expand...
I agree, what I meant is the LMFC will not be adequately bonded no matter what you do?
 
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