Trailer

[Oakey]

Hello...I have just taken on a new acct for a company that cleans up oil spills. Part of this task is to take a small trailer with a few pumps and maybe a heater and lights in it to these and other various job site locations (aka portable). I have already installed the sub panel inside it with an outside weatherproof twist lock setup to an 8/3 So cord etc. My question is.. I was wondering if I need to install a ground rod(s) at the sites?

 

[mdshunk]

Re: Trailer

I'll take a stab...
I was taught that if you block up the trailer with cinder blocks (much like you would a job trailer on a commercial job), it is now a "structure" and needs ground rods. If you just park it and chock the wheels, it's still mobile and you don't need ground rods.

 

[ramsy]

Re: Trailer

I've used pnumatic tools off portable-generator power, but portable electrical power is more interesting.

Taking a look, it seems if your portable power is over 600vac then an isolated-earth electrode is still required 2001 NEC 250.188(E).

In addition to weather proofing NEC 406.8(B)2b, the lower voltage exception 250.34 requires bonds to structural frames of portable power, rather than earth electrodes; but only where branch-powered hand tools & lighting are GFCI protected 511.12

And, you'll likely need extention cords 501.11 FPN:, lighting assemblies 501.9(B), and heating equipment 501.10(B) "clearly marked" and for Class 1 Div II around the oil & fuel spills. Portable power for personnel within this environment may need special bonds required in 501.16(B)

It also seems 250.190's warning about personnel touching a ground with portable power applies to all voltages.

I probably missed important details, but reading these sections, and searching for "portable" or "mobile" in Mike Holt's Classified Locations forum may reveal other issues that apply to hazmat cleanup.

This operation you're building from scratch sounds like it could use some help from this forum.

To me, protecting accounts and renewals might included some low-ball bidding, but like residential construction in my region, if generals won't pay a fair balance for minimum equipment and liability prevention its because they want foreign-language labor.

 

[Oakey]

Re: Trailer

Ths for the replies..So from these posts I assume I need to bond the frame to the sub panel intead of rods?

 

[5Spot]

Re: Trailer

Originally posted by Oakey:
Ths for the replies..So from these posts I assume I need to bond the frame to the sub panel intead of rods?

In the 2005 code, 550.4 comes about as close as you can get to describing your trailor and is thus subject to 550.16 which will answer your question.

 

[petersonra]

Re: Trailer

Article 550 is for trailers that are inhabited, not equipment trailers.

A PE I know and I did some serious research on this a while back and came to the conclusion that the NEC just does not cover this situation very well, if at all.

My suggestion is to make the installation safe, and not worry about the minimum requirements.

Bond the ground bar to the trailer structure. The last thing you want is for the trailer structure to become energized and not trip the OCPD.

 

[5Spot]

Re: Trailer

Originally posted by petersonra:
Article 550 is for trailers that are inhabited, not equipment trailers.

Well, I respectuflly disagree with your conclusion due to the following language of 550.4(A)

MOBILE HOME NOT INTENDED AS A DWELLING UNIT.

A mobile home not intended as a dwelling unit - for example, those equipped for sleeping purposes only, contractor's on-site offices, construction job dormitories, mobile studio dressing rooms, banks, clinics, mobile stores, or intended for the display or demonstration of merchandise or machinery - shall not be required to meet the provisions of the article pertaining to the number or capacity or circuits required. It shall, however, meet all other applicable requirements of this article if provided with an electrical installation intended to be energized from a 120-volt or 120/240-volt ac power supply system. Where different voltage is required by either design or available power supply system, adjustment shall be made in accordance with other articles and sections for the voltage used.

 

[petersonra]

Re: Trailer

I respectfully point out the language of 550.1.

I don't see any way you could twist the plain language of what this article covers to include a trailer that is never intended to have people in it other than to service equipment. Unless you consider the equipment to have a "home" and that home is the trailer.

 

[jbwhite]

Re: Trailer

if it were my crew, it would have sleeping arrangements in it after the first hour.

 

[5Spot]

Re: Trailer

Originally posted by petersonra:
I respectfully point out the language of 550.1.

I don't see any way you could twist ...

No twisting going on here; simply the interpretation of my local AHJ as of a month ago when I customized 8 mobile trailers for a defense department contractor. He specifically pointed me to 550.4(A) as the justification as to why the mobile trailers fall under the requirements of article 550.

Instead of attacking me personally by accusing me of "twisting" the meaning of the code, why don't you agree to disagree without being disagreeable about it. It's not too unusual to find individuals who have different interpretations about the language of the NEC. It doesn't make one person wrong or one person right; it just means there is a difference in interpretation and that should breed healthy and instructive debate, not personal attacks.

 

[iwire]

Re: Trailer

Boy I have been going back and forth on this between Bob P's view and 5Spot's view.

For whatever it is worth here is what I think and I am interested in what others think.

First we have the scope of 550 as Bob P noted.

As far as I understand the NEC an article can not extend beyond it's own scope.

550.1 Scope.
The provisions of this article cover the electrical conductors and equipment installed within or on mobile and manufactured homes, the conductors that connect mobile and manufactured homes to a supply of electricity, and the installation of electrical wiring, luminaires (fixtures), equipment, and appurtenances related to electrical installations within a mobile home park up to the mobile home service-entrance conductors or, if none, the mobile home service equipment.

Then we are confronted with 550.4 as 5Spot brought up.

550.4 General Requirements.
(A) Mobile Home Not Intended as a Dwelling Unit. A mobile home not intended as a dwelling unit ? for example, those equipped for sleeping purposes only, contractor?s on-site offices, construction job dormitories, mobile studio dressing rooms, banks, clinics, mobile stores, or intended for the display or demonstration of merchandise or machinery ? shall not be required to meet the provisions of this article pertaining to the number or capacity of circuits required. It shall, however, meet all other applicable requirements of this article if provided with an electrical installation intended to be energized from a 120-volt or 120/240-volt ac power supply system. Where different voltage is required by either design or available power supply system, adjustment shall be made in accordance with other articles and sections for the voltage used.

In my opinion we now must look at the NEC definition of mobile home.

Mobile Home. A factory-assembled structure or structures transportable in one or more sections that is built on a permanent chassis and designed to be used as a dwelling without a permanent foundation where connected to the required utilities and that includes the plumbing, heating, air-conditioning, and electric systems contained therein.
For the purpose of this Code and unless otherwise indicated, the term mobile home includes manufactured homes.

Now what I get from this is the following.

If I purchase a mobile home per the NEC definition and choose to use it for any another purpose than I must still follow Article 550.

However if I purchase a empty cargo trailer and turn it into an office, equipment trailer, bookmobile etc. than Article 550 does not apply as that cargo trailer was never designed to be used as a dwelling.

As a cargo trailer was never designed to be used as a dwelling it is not a mobile home per the the 550.2 definition. If it is not a NEC mobile home than 550.4 certainly can not apply to it as 550.4 is referring specifically to a mobile home used for something else.

Does that make sense?

So...what do you all think?

[ January 03, 2006, 05:51 AM: Message edited by: iwire ]

 

[George Stolz]

Re: Trailer

Iwire, I agree with your read on this, well put.

Originally posted by 5Spot:
Instead of attacking me personally by accusing me of "twisting" the meaning of the code...

5Spot, welcome to the forum.

I twist, poke, prod, knead, massage, thump, and skewer the code as a natural process of seeing if it could be interpreted another way. I don't mean to speak for Bob P, but that was a pretty mild statement to get amped up over. Stick around here and you'll see real heated arguments over code, amongest fellas who enjoy their opponent's company.

So simmer down, and stick around.

 

[iwire]

Re: Trailer

Originally posted by georgestolz:
that was a pretty mild statement to get amped up over. Stick around here and you'll see real heated arguments over code, amongest fellas who enjoy their opponent's company.

Yeah...what George said.

 

[5Spot]

Re: Trailer

[/QUOTE]Then we are confronted with 550.4 as 5Spot brought up.

550.4 General Requirements.
(A) Mobile Home Not Intended as a Dwelling Unit.

So...what do you all think? [/QB]

That's a great analysis of 550.4 iwire but in the case of my AHJ, his reasoning for applying 550.4 was that he felt the application of the wiring addition and modification applied to the language of 550.4 especially since the trailers are capable of being supplied by a 120/240-volt ac source.

It's really interesting and rewarding to see the variuos views on the interpretation of the code; one of the quotes I've always remebered from those who have taught me through this rewarding trade is; always look for reasons to apply the code in what you do, not reasons to avoid using it.

And then there's a spicy electrical contractor I worked for eons ago who said, "How much liability do you want to assume young man? You better make sure you follow the code when you're on my clock."

Hey, didn't mean to get my undies in a wad either.

 

[iwire]

Re: Trailer

Originally posted by 5Spot:
That's a great analysis of 550.4 iwire but in the case of my AHJ, his reasoning for applying 550.4 was that he felt the application of the wiring addition and modification applied to the language of 550.4 especially since the trailers are capable of being supplied by a 120/240-volt ac source.

Well I think your AHJ made a mistake, no offense meant they are only human as well.

Was the trailer in question originally designed as a mobile home or not I think that is the key.

I do not think that 550.4 is written that clearly.

Just my opinion, Bob

 

[Oakey]

Re: Trailer

The main reason for me posting this originally was I couldn't get a clear interpretation of 550.4 from any person I asked locally, even my former boss who I consider to be a reliable source. I appreciate all the points of view as I have applied the bonding suggestion and other points made here as well. Maybe could be a good topic for the 2008 code?