Bonding of FMC

[DPW]

As a practice, we always install an EGC in every raceway and bond it to any metal including metal junction boxes.

Sometimes when a flexible metal conduit (FMC) is terminated into a diecast FMC fitting (90 degree) that is connecting a motor (on moveable base of a fan), our electricians will wrap the end of the FMC with black tape to get a better grip. Although the other end of the FMC has a metallic bond (through a diecast fitting) and that an EGC is installed, is this a code violation under
Article 250?

 

[LarryFine]

I'd say that only one end need be bonded.

I'd also say that, if you pay attention to which end of the spiral is on the outside, and place the other end in whichever connector has the better grip (angle connector, usually) or less physical stress on it (or secured by a clamp, say), you shouldn't need tape.

As an example, when I hang a fixture whip from a ceiling box, I always make sure the outside end of the flex is in the box, because the connector has a better grip on the outside end.

 

[Smart $]

In addition to Larry's advice, I'll go one step further and say don't use tape. I would consider it a violation of not being installed per its listing, regardless of whether it is actually serving the purpose of a grounding conductor or not.

 

[Pierre C Belarge]

In addition to Larry's advice, I'll go one step further and say don't use tape. I would consider it a violation of not being installed per its listing, regardless of whether it is actually serving the purpose of a grounding conductor or not.

Are you stating that using tape is a violation?
If so, please cite us a reference in the NEC that you are perusing.

 

[infinity]

Are you stating that using tape is a violation?
If so, please cite us a reference in the NEC that you are perusing.

I agree with Smart, putting tape around a piece of metal flex before installing the connector would be a violation. The flex and connector should be listed to work with each other.

 

[Smart $]

Are you stating that using tape is a violation?
If so, please cite us a reference in the NEC that you are perusing.

348.6 Listing Requirements. FMC and associated fittings
shall be listed.

As far as I know, "tape" is not and will never be an associated fitting, let alone listed as such. :smile:

Additionally, are the manufacturers' instructions part of the listing? Can you show us a manufacturer's instruction to tape around FMC where it is to mate with a connector?

 

[Pierre C Belarge]

I am not sure if the OP meant taping the FMC and the entering into the fitting. That is clearly not an approved method.
I thought he meant tapping the fitting to help keep it together.

and listing of fittings for FMC is a requirement as well, I understand that.


I have seen installers using ty-wire wrapped around the fitting and then the FMC itself to help hold it in the fittng.

 

[RICK NAPIER]

I have seen this installation a number of times where they tape the FMC before it goes under the connector. In fact just yesterday on a 60HP motor. It always fails.

 

[SEO]

Sure makes you wonder what's going on in the installers mind?

 

[LJSMITH1]

I agree with Smart, putting tape around a piece of metal flex before installing the connector would be a violation. The flex and connector should be listed to work with each other.

Any fitting designed and listed for use with FMC should be connected and secured using nothing more than a screwdriver (and hammer for locknut end). If the FMC fitting is not sized for the FMC, then there is a clear mis-application of the fitting. Most fitting specifications will state what size FMC it is designed for. If the FMC goes by trade size, then thats what you use. If they have a decimal size, you cannot convert to the closest fraction and equate it to a trade size (i.e. .615" OD FMC does not necessarily equal a 1/2" trade size, etc.). Tape used to build up the OD of FMC tells me that the fitting is sized improperly for the particular OD of the FMC. FMC Trade sizes are clearly defined in UL 1, Table 9.1. Anything outside this approved range is unique (like USL-120 Superflex), and must be specifically tested by the manufacturer.

The manufacturer of the fitting should clearly indicate (on the label or spec sheet), the approved/listed sizes of FMC used with the particular fitting.

I agree with others that this is an unapproved use of a fitting and will most certainly result in a lack of bonding continuity and mechanical pull strength between the fitting and the FMC. It certainly violates NEC 250.96, 250.118(5), 348.60, and 348.6.