230.43

[texie]

Per 230.43 (15) and you are using LFMC between, say, a meter socket and a service disconnect you need to install a SSBJ. But if you have a meter socket with a bonding jumper (most would have a permanent bond anyway) and you have the neutral bonded at the service disconnect this would comply with 250.92 and that is all you need for a fault return path. What purpose does the SSBJ serve?
After all, if you used, say PVC, no bonding SSBJ would be required. I realize that LFMC is metallic and can't carry the fault current but how would a SSBJ help if you already comply with 250.92 by bonding to the neutral at each end?

 

[wwhitney]

Per 230.43 (15) and you are using LFMC between, say, a meter socket and a service disconnect

If I'm reading 230.43(15) correctly, you can't use it as the sole wiring method between a meter socket and disconnect. 230.43(15) says: "between a raceway, or between a raceway and service equipment." So I'm seeing an allowance to use up to 6' of it in conjunction with another raceway, e.g. where you need some funky bends.

In that case, if you are allowed to use two segments of it (is the 6' limit in aggregate or per segment?) as in enclosure - metallic raceway - LFMC - metallic raceway - LFMC - enclosure, and the raceway is metallic, you'd need the SSBJ for at least one of the LFMC segments to bond the metallic raceway between the LFMC segments. I agree that it doesn't seem necessary if you have only one segment of LFMC, barring something odd like non-metallic raceway - metallic raceway - LFMC.

Cheers, Wayne

P.S. In the 2008 NEC it says "between raceways" rather than "between a raceway," which makes more sense. But I'm assuming that's what "between a raceway" means.

 

[texie]

I, too, noticed the convoluted language. But it seems to me that the physics of this in this application don't seem to hold water. Thanks for your thoughtful response. Let's see if others see the oddity of this or perhaps can help me understand the reasoning.

 

[infinity]

I realize that LFMC is metallic and can't carry the fault current but how would a SSBJ help if you already comply with 250.92 by bonding to the neutral at each end?

The SSBJ is for clearing a fault within the LFMC so that is not relying on the standard locknuts and connectors.

 

[wwhitney]

The SSBJ is for clearing a fault within the LFMC so that is not relying on the standard locknuts and connectors.

So you're saying the SSBJ should have one end connected to the LFMC (how?) and the other end connected to a good fault clearing path, e.g. the enclosure at either end? That would make sense, but I don't see how the language in 230.43(15) says that.

Cheers, Wayne

 

[infinity]

So you're saying the SSBJ should have one end connected to the LFMC (how?) and the other end connected to a good fault clearing path, e.g. the enclosure at either end? That would make sense, but I don't see how the language in 230.43(15) says that.

Cheers, Wayne

Use a bonding bushing on one end with a SSBJ.

 

[wwhitney]

Use a bonding bushing on one end with a SSBJ.

But one of the options in 230.43(15) is to use LFMC "between raceways" (after correcting the post-2008 typo that was introduced). How do you do that when the LFMC does not terminate at an enclosure?

And again, there's nothing in 230.43(15) about connecting the SSBJ to the LFMC.

Cheers, Wayne

 

[infinity]

Look at 250.92(B)(4).

 

[wwhitney]

Look at 250.92(B)(4).

Not following the relevance of that. Let's be a bit more concrete:

First, 230.43(15) does not allow FMC alone to be used from a meter enclosure to a service disconnect enclosure. It may only be used between a raceway and an enclosure, or between raceways.

So let's say you have Meter enclosure -- Threadless RMC connector -- RMC -- RMC/FMC threadless transition coupling -- FMC -- FMC connector -- Service Disconnect enclosure.

250.92(B)(3) says that "Threadless couplings and connectors if made up tight for metal raceways and metal-clad cables" are sufficient for service bonding. So that would cover the threadless RMC connector, the RMC/FMC threadless transition coupling, and the FMC connector. If we have no "impaired connections" at either enclosure, then 250.92 on service bonding is satisfied.

Now 230.43(15) says we need "a supply-side bonding jumper routed with the flexible metal conduit (FMC) or the liquidtight flexible metal conduit (LFMC)". So where are the two ends of the SSBJ supposed to connect?

Thanks,
Wayne

 

[infinity]

Now 230.43(15) says we need "a supply-side bonding jumper routed with the flexible metal conduit (FMC) or the liquidtight flexible metal conduit (LFMC)". So where are the two ends of the SSBJ supposed to connect?

You say with the better word is for. It SSBJ is for bonding the service raceway on either end as in the code section I posted.

 

[wwhitney]

You say with the better word is for.

I didn't choose "with", 230.43(15) says "with". If the CMP meant "for," wouldn't they say "for," rather than "with"? Or something explicit like "with a supply-side bonding jumper bonded to the FMC or LFMC"?

It SSBJ is for bonding the service raceway on either end as in the code section I posted.

But as I indicated, for the example configuration, 250.92 doesn't require any bonding jumpers. So we can't say that 230.43(15) is referencing the SSBJ required by 250.92, as 250.92 doesn't require one (at least in this example).

Cheers, Wayne

 

[infinity]

I didn't choose "with", 230.43(15) says "with". If the CMP meant "for," wouldn't they say "for," rather than "with"? Or something explicit like "with a supply-side bonding jumper bonded to the FMC or LFMC"?


But as I indicated, for the example configuration, 250.92 doesn't require any bonding jumpers. So we can't say that 230.43(15) is referencing the SSBJ required by 250.92, as 250.92 doesn't require one (at least in this example).

Cheers, Wayne

You're off on a tangent that I don't understand. The OP is asking about the required SSBJ for a metal raceway between the meter enclosure and the service disconnect. I have answered that question, it bonds the service raceway by utilizing something beyond a standard lcoknut as required by 250.94.

What purpose does the SSBJ serve?

 

[wwhitney]

You're off on a tangent that I don't understand. The OP is asking about the required SSBJ for a metal raceway between the meter enclosure and the service disconnect. I have answered that question, it bonds the service raceway by utilizing something beyond a standard lcoknut as required by 250.94.

Somehow we are talking past each other. You brought up 250.92, when the OP is about 230.43(15). While they are related, they are different sections.

First, my reading of 250.92 is that the phrase "Standard locknuts or bushings shall not be the only means for the bonding required by this section" means that you can't use, for example, a threaded piece of RMC as a service raceway, with two locknuts to connect the RMC to the enclosure. But 250.92(B)(3) says that "Threadless couplings and connectors if made up tight for metal raceways and metal-clad cables" are OK for bonding. That means if you use, say, EMT as your service raceway, a standard EMT connector is sufficient for service bonding, it complies with 250.92(B)(3). Agreed?

If so, then in general there isn't any need for an SSBJ with a metal service raceway. So pointing to 250.92 doesn't explain why 230.43(15) requires an SSBJ whenever you use FMC/LFMC as a service raceway. And saying that the SSBJ is to bond the FMC/LFMC doesn't explain why 230.43(15) says the SSBJ is to be "routed with" the FMC/LFMC, rather than "routed to one end" or "bonded to" or whatever.

In case you haven't looked up the text of 230.43(15), it is:

230.43 Wiring Methods for 1000 Volts, Nominal, or Less. Service-entrance conductors shall be installed in accordance with the applicable requirements of this Code covering the type of wiring method used and shall be limited to the following methods:

. . .
(15) Flexible metal conduit (FMC) not over 1.8 m (6 ft) long or liquidtight flexible metal conduit (LFMC) not over 1.8 m (6 ft) long between a raceway [sic, should be "between raceways"], or between a raceway and service equipment, with a supply-side bonding jumper routed with the flexible metal conduit (FMC) or the liquidtight flexible metal conduit (LFMC) according to the provisions of 250.102(A), (B), (C), and (E)

Cheers, Wayne

 

[infinity]

Wayne, thanks for posting the code section. I didn't have access to the NEC when I answered to original question and I missed the 230.43 part. Sorry for the confusion.

 

[texie]

The SSBJ is for clearing a fault within the LFMC so that is not relying on the standard locknuts and connectors.

Perhaps you are not understanding my point. If you have the enclosures bonded to neutral at each end as you are permitted to do for any metallic enclosure on the line side of a service disconnect you already have a compliant fault return path. The addition of a SSBJ for the LFMC installed per 250.102 (A) (B) (C) and (E) does nothing to protect the LFMC. In other words the LFMC is not even part of the fault return path. Just as if the wiring method was non metallic.
To be clear, I understand the requirements for a circuit on the load of a service that has that has LFMC as part of the raceway system and why you need an EGC around the LFMC.

 

[wwhitney]

The addition of a SSBJ for the LFMC installed per 250.102 (A) (B) (C) and (E) does nothing to protect the LFMC.

It might if the SSBJ were bonded to the LFMC, but 230.43(15) doesn't instruct us to do this.

My best guess is that the 230.43(15) is instructing us to use an SSBJ as a bonding jumper around any segment of FMC or LFMC, since it is not a very good fault clearing path, as indicated by the limitations put on its use as an EGC in 250.118.

That seems redundant whenever the FMC or LFMC connects directly to a service enclosure, or when it connects to other metallic raceways that connect directly to service enclosures. But there are scenarios where an SSBJ or some other method would be required, e.g. enclosure - RMC - FMC - RMC - LFMC - RMC - enclosure. 230.43(15) doesn't want to get into that level of detail, so it just requires one all the time.

If it were a general requirement that every metallic service raceway should be bonded at both ends, then the requirement in 230.43(15) would make more sense. But as far as I know, if you have enclosure - RMC - PVC - RMC - enclosure, there's no requirement to bond around the PVC.

Cheers, Wayne