Bonding around LFMC

[jrannis]

I have a situation where I added a fourth set of conductors to increase the ampacity of a feeder from an optional standby generator.
The existing installation consisted of three 2-1/2" rigid with four 350 mcm. The conduit terminated into the generator enclosure and then changed over to Sealtite for the last 18".
The conduit I added terminated with the same materials but I added a 3/0 ground in my conduit with the 350s.
The inspector suggested that I should remove the ground wire.

Am I missing something?

 

[benaround]

Is the LFMC installed for flexiblity to the generator ? If yes, then they all should have EGC.

 

[don_resqcapt19]

The installation of an EGC in only one of the conduits creates a 310.4 violation, but Frank is correct that the LFMC can't be used as the equipment grounding conductor for this application. The easiest solution would be to remove the EGC that you installed and install external bonding jumpers around each of the LFMCs.

 

[Smart $]

... Am I missing something?

Not enough info to make that determination.

1) First, which code cycle?
2) Where is the disconnecting means located?
3) Is this an SDS or non-SDS system?
4) If SDS, where is the system bonding jumper located?
5) Do the pre-existing runs not have a grounding conductor?

Earlier cycles permitted using the grounded conductor to be used for grounding. Typically you have a grounding conductor in all conduits or none. The latter of which I believe the inspector is thinking. However, LFMC is not permitted for grounding if installed for flexibility.

 

[don_resqcapt19]

I don't think that the "flexibility" issue applies here. LFMC has never been permitted as the EGC for circuits that have 350kcmil conductors.

 

[yired29]

No code book in front of me but I thought 60 amps was the threshold before a EGC is required. 250.118 I believe.

 

[yired29]

Got my code book 250.118 (6) c. If paralled then all ECG in all paralled raceways would have to be sized based on 250.122 per 250.104 (D)

 

[Smart $]

I don't think that the "flexibility" issue applies here. LFMC has never been permitted as the EGC for circuits that have 350kcmil conductors.

I wouldn't say 350.60 doesn't apply here. While size and conductor overcurrent rating eliminate the LFMC from being used as an EGC, 350.60 is where an EGC is required to be run where installed for flexibility. It is only when not installed for flexibility does 250.118(6) have any effect. Analogous to the "chicken or the egg" causality dilemma.

 

[DARUSA]

Equipment bonding jumper

Equipment bonding jumper

350.60 ?
250.118 6 Listed liquidtight flexible metal conduit meeting all the following conditions: See related UL
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.

 

[DARUSA]

I would consider the flexibility required in this case due to the vibration of the Generator.250.118 6 e. apply

 

[DARUSA]

Got my code book 250.118 (6) c. If paralled then all ECG in all paralled raceways would have to be sized based on 250.122 per 250.104 (D)

I agree ., Or you place the ground wire in all conduit based on 250.122 table or you install your EBJ outside of the raceway

 

[Smart $]

I would consider the flexibility required in this case due to the vibration of the Generator.250.118 6 e. apply

We may be talking an EBJ rather than an EGC...

350.60 Grounding and Bonding. Where used to connect
equipment where flexibility is required after installation, an
equipment grounding conductor shall be installed.
Where flexibility is not required after installation,
LFMC shall be permitted to be used as an equipment
grounding conductor when installed in accordance with
250.118(6).
Where required or installed, equipment grounding conductors
shall be installed in accordance with 250.134(B).
Where required or installed, equipment bonding jumpers
shall be installed in accordance with 250.102.

 

[jrannis]

Is the LFMC installed for flexiblity to the generator ? If yes, then they all should have EGC.

I believe that the flexibility is necessary for vibration isolation.

 

[jrannis]

The installation of an EGC in only one of the conduits creates a 310.4 violation, but Frank is correct that the LFMC can't be used as the equipment grounding conductor for this application. The easiest solution would be to remove the EGC that you installed and install external bonding jumpers around each of the LFMCs.

This is what the inspector suggested.
Could I simply disconnect the internal ground and bond the conduit around the sealtite to the enclosure using a ground clamp and a lug?
Do I really need to pull the ground out?
Its about a 50' run with four 90s (of course)

 

[don_resqcapt19]

This is what the inspector suggested.
Could I simply disconnect the internal ground and bond the conduit around the sealtite to the enclosure using a ground clamp and a lug?
Do I really need to pull the ground out?
Its about a 50' run with four 90s (of course)

Leaving the conductor in the raceway, even if it is not connected at either end, is a violation of 310.4, however I can't see how it would cause any problems and you may get the inspector to let you leave it in place.