service bonding question

[iwire]

Stew here is a section of 4" RMC containing service conductors that had a fault.

Luckily this was on the outside of the building.

 

[stew]

not to beat this to death but the mast comes down into the meter from the roof and enters the house for only about 18 or 20 inches at most before it enters the meter base. The service panel is about 4 inches from the meter panel connected with a short nipple. the meter base is in one bay of studs and the panel in the adjacent bay which is a very common installation in our area when flush meter panels are used. New construction houses especially the hiher end units use this method a lot. Hides the pie and the only thing you see is the meter at the wall. this is also done with underground feeds as well wjere about 5 ft of pipe enters the wall but this is usually pvc.

 

[iwire]

Stew if your interested here is the handbooks commentary on this issue.

No maximum distance is specified from the point of entrance of service conductors to a readily accessible location for the installation of a service disconnecting means. The authority enforcing this Code has the responsibility for, and is charged with, making the decision as to how far inside the building the service-entrance conductors are allowed to travel to the main disconnecting means. The length of service-entrance conductors should be kept to a minimum inside buildings, because power utilities provide limited overcurrent protection and, in the event of a fault, the service conductors could ignite nearby combustible materials.
Some local jurisdictions have ordinances that allow service-entrance conductors to run within the building up to a specified length to terminate at the disconnecting means. The authority having jurisdiction may permit service conductors to bypass fuel storage tanks or gas meters and the like, permitting the service disconnecting means to be located in a readily accessible location. However, if the authority judges the distance as being excessive, the disconnecting means may be required to be located on the outside of the building or near the building at a readily accessible location that is not necessarily nearest the point of entrance of the conductors. See also 230.6 and Exhibit 230.15 for conductors considered to be outside a building.

 

[stew]

yes thanks bob ive read that . I always design my new installs or service upgrades so that ther will only be at most a short nipple to the service disconnect in the homes panel. in the case cited i was stuck with what I had of course.unles I wanted to compltley redesign and redo the meterbas and mast. Perfectly fine equippment that would have cost a lot to replace.( out of curiosity whats a senior member? do they know my age?)

 

[izak]

as stated before, that installation is Very common in California, on houses 20 or 30 years old, with recessed meter/panel combos with Bulldog-Push Matic breakers... the equipment was designed and listed that way, how could it be a violation...

what i see as a violation in the OP that no one that i saw pointed out is that he is using the Bond Bushing as a LOCKNUT inside the can and that is Definitely not correct... Set screws or not, you Cannot use a Bushing as a Locknut

 

[dlhoule]

It appears that your state has set a number to "nearest the point of entrance". However, I would include the service riser in the 15'. I have seen what happens to even rigid conduit with a fault on the line side of the service OCPD. It provides very little protection from fire. It is my opinion (a very minority opinion) that the words "nearest the point of entrance" mean exactly that. The service disconnect must be on the inside of the wall where the conductors enter the building. No allowance of any lenght. If it was up to me, the service OCPD would be required to be on the outside of the structure.
Don

I agree with Don on this issue. I find it ironic that I can run from meter with 150' of SEU before I enter house to service equipment, but I can't use 6' of rigid to go from meter to panel.

 

[iwire]

I agree with Don on this issue. I find it ironic that I can run from meter with 150' of SEU before I enter house to service equipment, but I can't use 6' of rigid to go from meter to panel.

I agree that it should be short inside the building. I don't see any issue outside the building.

What max length could we set outside, short of requiring the power company to provide OCP at the pole we are stuck with the service conductors running down or around the outside of the building.

 

[infinity]

what i see as a violation in the OP that no one that i saw pointed out is that he is using the Bond Bushing as a LOCKNUT inside the can and that is Definitely not correct... Set screws or not, you Cannot use a Bushing as a Locknut

Do you have an article reference which says this? I thought that rigid service raceways needed two locknut's but I can't find an NEC reference.

 

[77401]

how do you get a violation of that section don? the violation is section 250.90(B)the pargraph after(4) which has to do with standard locknuts not being the sole bonding means in this section for services.

250.92(b)????

 

[dlhoule]

I agree that it should be short inside the building. I don't see any issue outside the building.

What max length could we set outside, short of requiring the power company to provide OCP at the pole we are stuck with the service conductors running down or around the outside of the building.

Well, I agree that it should be as short as possible, especially going inside. I do think that when you get into longer lengths on the outside with SEU unprotected til the point of entry, especially with vinyl or alum siding, it is just as hazardous as going inside with 10' or so of RMC.

 

[infinity]

250.92(b)????

I don't see where that requires two locknut's on a rigid conduit.

 

[George Stolz]

what i see as a violation in the OP that no one that i saw pointed out is that he is using the Bond Bushing as a LOCKNUT inside the can and that is Definitely not correct... Set screws or not, you Cannot use a Bushing as a Locknut

From the UL Certifications Directory:

Grounding and Bonding Bushings — Bonding bushings for use with conduit fittings, tubing (EMT) fittings, threaded rigid metal and intermediate metal conduit, or unthreaded rigid metal and intermediate metal conduit are provided with means (usually one or more set screws) for reliably bonding the bushing (and the conduit on which it is attached) to the metal equipment enclosure or box. They provide the electrical continuity required by the NEC at service equipment and for circuits rated over 250 V. Means for connecting a grounding or bonding wire are not provided and if there is need for such a conductor a grounding bushing should be used.

Grounding bushings for use with conduit fittings, tubing (EMT) fittings, threaded rigid metal and intermediate metal conduit, or unthreaded rigid metal and intermediate metal conduit have provision for the connection of a bonding or grounding wire or have means for mounting a wire connector available from the manufacturer. Such a bushing may also have means (usually one or more set screws) for reliably bonding the bushing to the metal equipment enclosure or box in the same manner that this is accomplished by a bonding bushing. Grounding bushings provide the electrical continuity required by the NEC at service equipment and for circuits rated over 250 V. They may be used with or without a bonding or grounding conductor as determined by the bonding or grounding function that is intended to be accomplished.

Insulating throat liners in grounding or bonding bushings are suitable for temperatures of 150?C if they are black or brown in color. Unless otherwise marked, insulating throat liners of any other color are suitable for temperatures of 90?C.

Grounding and Bonding Locknuts — Grounding and bonding locknuts serve in a manner similar to grounding and bonding bushings except they do not provide abrasion protection for the conductor at the end of the conduit.

I'd say you're correct, the bonding bushing is not supposed to be used as a locknut. In this circumstance, with a locknut on the outside of the enclosure, do you think it will not hold securely?

I remember the last time I dealt with bonding a LFMC connector, the locknut was too thick to install the bonding bushing effectively. I forget if I ditched the locknut or what, it's been a while. I know the connector did not seat well against the can without the locknut, but I'm not sure what my solution was.

In that case, I did not have a locknut to wrench it down tight to.

Good catch, Izak.

 

[infinity]

I'd say you're correct, the bonding bushing is not supposed to be used as a locknut. In this circumstance, with a locknut on the outside of the enclosure, do you think it will not hold securely?

I disagree, where does it say that? And where does it say that you need two locknut's?

What is the difference between an EMT connector with one tightened locknut and a bonding bushing with one tightened locknut? Either way the raceway is secured to the box. There is a good photo of this on page 219 in the 2005 NEC Handbook.

 

[iwire]

Check out this small snippet from 300.4(F)

Conduit bushings constructed wholly of insulating material shall not be used to secure a fitting or raceway.

That seems to me to leave the door open for a bushing that is partially or fully metal to secure conduits or fittings.

 

[infinity]

Check out this small snippet from 300.4(F)



That seems to me to leave the door open for a bushing that is partially or fully metal to secure conduits or fittings.

Thanks Bob, my thoughts exactly. This has come up before but I've yet to see where it says that says a metal bushing needs two locknut's.

 

[George Stolz]

I disagree, where does it say that?

Well, right next to the - hey! Look over there!

I take that back. It's not prohibited anywhere I've looked.

And where does it say that you need two locknut's?

How would the rigid not slide into the enclosure without a locknut on the outside of the box? I'm not saying two outside the box, just one.

There is a good photo of this on page 219 in the 2005 NEC Handbook.

Can someone post the image?

 

[iwire]

How would the rigid not slide into the enclosure without a locknut on the outside of the box? I'm not saying two outside the box, just one.

The lock nut at the other end of the raceway?


I think what we are saying is one locknut on the outside and just a metal bonding bushing on the inside.

 

[infinity]

I think what we are saying is one locknut on the outside and just a metal bonding bushing on the inside.

Yes,exactly.

 

[don_resqcapt19]

300.4(F) ... Conduit bushings constructed wholly of insulating material shall not be used to secure a fitting or raceway.

This section implies that a locknut is not required on the inside of the enclosure if a metal bushing is used.
Don