348.60 EGC required for FMC

[Minuteman]

The chapter that we are in is over Article 250 for my 2nd year class. I think the author missed something.

Here is the question: You are to connect an AHU. You decide to use 3' of 1/2 FMC and you realize that since it has a motor it is likely to vibrate. Neither the FMC nor the connectors are listed for grounding. Is an EGC required? a. No b. Yes

The answer key says the correct answer is, "a. No". It most likely is just a typo, because the key references 348.60 Grounding and Bonding.

I am I right and the answer key is wrong?

 

[infinity]

Take a look at 250.118(5)(a)-(d).

 

[hurk27]

I would also say NO, as since any chapter 3 wiring method could have been used to wire the AHU that was appropriate for the location, and this would have included EMT, RMC, Etc... which are ridged, the use of the FMC was not for flexibility, just convenience, The AHU is not likely to be moved around right?, vibration is not a reason for a requirement to use FMC for flexibility so 348.60 does not apply.

trick question

 

[Minuteman]

Take a look at 250.118(5)(a)-(d).

I saw that Rob, especially (d).

However, hurk has me rethinking. Since vibration may not be an issue, except the question has the installer assuming that vibration might be an issue. So the question has a curve ball, and I'm a sucker for a good curve ball. :roll:

 

[hurk27]

I saw that Rob, especially (d).

However, hurk has me rethinking. Since vibration may not be an issue, except the question has the installer assuming that vibration might be an issue. So the question has a curve ball, and I'm a sucker for a good curve ball. :roll:

Yes but the question still doesn't meet all of the requirements.

Listed flexible metal conduit that is not listed for grounding, meeting all the following conditions:
a. The conduit is terminated in fittings listed for grounding.
b. The circuit conductors contained in the conduit are protected by overcurrent devices rated at 20 amperes or less.
c. 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).
d. The conduit is not installed for flexibility.

even if the FMC is not listed for grounding, it still has to terminate in a fitting listed for grounding.

So I reverse my opinion

 

[Minuteman]

Bingo... 250.118 (a)!!! So, the book was right.






and Rob too!

 

[Volta]

Yes but the question still doesn't meet all of the requirements.


even if the FMC is not listed for grounding, it still has to terminate in a fitting listed for grounding.

So I reverse my opinion

True, but for last cycle. In 2008 Sub-section 250.118(5)a. says "The conduit is terminated in listed fittings".

 

[hurk27]

Bingo... 250.118 (a)!!! So, the book was right.






and Rob too!

Ok you really confused me?

To me the book was wrong and you were right? right? I think? or is that the answer key was wrong and the book was right? ok I'm cornfused

from your question: Neither the FMC nor the connectors are listed for grounding

requirement for FMC to be used as a EGC (not requiring a wire EGC in it)

a. The conduit is terminated in fittings listed for grounding.

 

[Minuteman]

Ok you really confused me?

To me the book was wrong and you were right? right? I think? or is that the answer key was wrong and the book was right? ok I'm cornfused


requirement for FMC to be used as a EGC (not requiring a wire EGC in it)

Confused myself... I meant to say, that I am right and the book/answer key is wrong. :grin:

The answer key has "a. No" for the answer. (Is an EGC required?)

 

[hurk27]

True, but for last cycle. In 2008 Sub-section 250.118(5)a. says "The conduit is terminated in listed fittings".

I don't think that this changed much other then removing the "listed for grounding, as a listed fitting is required to meet the grounding and bonding properties that was and has always been recognized by UL, I would believe this change was to remove the confusion that a specific fitting had to be specially listed for just grounding, which I believe was never the intent.

I might be wrong about this but I just spent about an 30 miniutes trying to find this change in the 2007 ROC.s or even in the ROP's but could not come up with where this change was made?

There was many proposals in the 2005 cycle that danced all around this section but non hit right on this wording change?

Guess it was snuck in:roll: