grounding electrode at a office trailer

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romeo

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Hi everyone I haven't posted here for a while but am always watching all on the forum. I hope all of you are well,and getting along with NEC 2008.

I am hoping for an opinion from some or all of you.

Yesterday I did an inspection of a office trailer for a business, that will be permanent ( not that it makes any deference ). I failed the inspection because there is no grounding electrode at the trailer panel.

The trailer panel has a feeder from a service located about 10 ft. from it with a Main Breaker at that location. The electrician feels that there is no requirement for a grounding electrode at the trailer panel because there is one at the service.

My opinion is that Art. 100 definition is that it is a structure,

Sec. 250.32 (A) requires that it will have a grounding electrode system, in accordance with part III of articale 250.

Sec.250.56 in part III applies to the 25 ohm or less rule, should ground rods serve as the electrodes. So I am telling him that he may need to provide 2 ground rods. I always felt that was the case even before NEC 2008.

Thanks to all Romeo
 
Romeo,
I haven't found this in the NEC either. It does exist in my states building code. An inspector gave one of the 'what-if's. What would happen if the EGC from the meter pedestal or other service point was damaged. The entire metal mass could become energized. My jurisdiction requires a ground rod at the point of service and at the trailer.
 
IMO It's a structure without a doubt, I always drive rods at trailers.

Not sure they will do anything but I install them anyway.
 
Romeo,

Good to hear from you agian!! This building falls under 550.4 , do you agree?

If you do, then how do you feel about 550.16 'Grounding'.

To me it says the grounding of both electrical and non-electrical metal will

be thru the green wire in the feeder wiring to the service ground located

adjacent to the location.

IMO, this thing comes prebuilt and is preinspected , it has a label inside for

any requirements needed, and a ground rod(s) is not one of them.

Personally, I wouldn't instruct anyone to mess with what is already there.

edit: I wanted to add that the service equipment falls under 550 not 230 per 550.4(C)
 
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romeo said:
The trailer panel has a feeder from a service located about 10 ft. from it with a Main Breaker at that location. The electrician feels that there is no requirement for a grounding electrode at the trailer panel because there is one at the service.

My opinion is that Art. 100 definition is that it is a structure,

Sec. 250.32 (A) requires that it will have a grounding electrode system...
Click to expand...

romeo,

The electrician may be right because it sounds like the existing electrode is only 10'+/- away. I'd think that is close enough for the electrode system to expand?

His new GEC does need to be at least a #6, 250-66(A)
 
In the light of electrodes purpose 250-4(A)(1) the length of the GEC should matter. As example see 800-100(A)(4) is 20', 820-100(A)(4) is 20', & 830-100(A)(4) is 20'.

You may require another electrode at the trailer panel to eliminate the GEC length, I think I would:)
 
tryinghard said:
Except 550 is for Mobile Homes, Manufactured Homes, and Mobile Homes Parks

This is an office trailer :)
Click to expand...
Check out 550.4 General Requirements, (A) Mobile Home Not Intended as a Dwelling Unit.

Assuming by the OP's use of the word trailer, this unit has the typical mobile/manufactured home chassis under it.
 
Smart $ said:
Check out 550.4 General Requirements, (A) Mobile Home Not Intended as a Dwelling Unit...
Click to expand...

Wow, keep reading, "...not intended as a dwelling unit - for example, those equipped for sleeping purposes only, contactor's on-site offices"

I don't now how this fits with 545-3 & 12, maybe manufactured buildings are not considered trailers/mobile?

benaround said:
Romeo, This building falls under 550.4 , do you agree? If you do, then how do you feel about 550.16 'Grounding'. To me it says the grounding of both electrical and non-electrical metal will be thru the green wire in the feeder wiring to the service ground located adjacent to the location.
Click to expand...

I agree with benaround and Smart $ it seems 550-16 applies but that means the service equipment must meet the distance and installation specs in Article 550 as well.

I think I'd provide a new electrode, again in light of its purpose (and it seems distance/length does matter). What's most critical is NOT bonding the neutral.
 
Smart $ said:
Check out 550.4 General Requirements, (A) Mobile Home Not Intended as a Dwelling Unit.
Click to expand...

This is talking about a mobile home that was built and listed as a Mobile home and now has found new life as some other use.

550 does not apply to a unit that was manufactured to be an office trailer from the start.

Any office trailer I have seen is listed as a 'Manufactured Building'
 
Sounds like this office trailer may not fit in with Article 550 (it's interpretive), it certainly is a structure and this causes the need for the electrode 250-50. Install it!
 
I did a Google search for ' Modular 101 ' an article written by Mike Roman, a

member of the Modular Building Institute was quite informitive.

It starts off by saying, if you want to find a 'portable classroom' in the Yellow

Pages you should start at ' Trailer Renting & Leasing ' as the bulk of the

Modular Building industry particapants are listed there.

Posters in this thread might see things more clearly if they read it.
 
tryinghard said:
Sounds like this office trailer may not fit in with Article 550 (it's interpretive), it certainly is a structure and this causes the need for the electrode 250-50. Install it!
Click to expand...

Somewhere on this 'thing' will be a tag, if the tag says 'Manufactured Building" then 545 applies. If the tag says 'Mobile Home' then 550 applies. :smile: I usually find the tag near the electrical panel on manufactured buildings, I don't work on Mobile homes. :smile:
 
romeo said:
The trailer panel has a feeder from a service located about 10 ft. from it with a Main Breaker at that location. The electrician feels that there is no requirement for a grounding electrode at the trailer panel because there is one at the service.
Click to expand...

How long will the GEC be if the electrician uses the existing electrode along with Article 550?

If using 550 will the GEC be continuous 250-64(C)?

I would use the lengths in Articles 800, 820, & 830 as example for maximum length on this project, their all used for the same purpose.

In my opinion whatever this unit maybe labeled is not relevant; its being used as an on site mobile construction office. I gotta say I've never hooked up a construction office as per 550-10, 550-32 which doesn't make it right but it makes all my inspectors [& myself] wrong.

I'm hung up on the purpose of grounding but I think its a safe place to hang!
 
iwire said:
Somewhere on this 'thing' will be a tag, if the tag says 'Manufactured Building" then 545 applies. If the tag says 'Mobile Home' then 550 applies. :smile: I usually find the tag near the electrical panel on manufactured buildings, I don't work on Mobile homes. :smile:
Click to expand...
Even if this falls under 545, a GE is not required "at" the structure if the service disconnect is remote to the structure. 545.12 simply says that provisions are to be made for routing a GEC from the "supply" to the point of attachment to the grounding electrodes. It does not specify the electrode(s) location(s). So the location of GE(s) goes back to 250, and 250.32(A) Exception eases the requirement for GE(s) at structure(s).
 
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