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#77491 06/15/01 09:46 AM
Joined: Dec 2000
Posts: 84
C
cinkerf Offline OP
Member
A medical trailor is going to be transported to our Firefighters Training Academy. It will be used for testing for 4 days and then taken away. It will come equipped with a 60 amp. 120/240V. 60A. 4W. power cable and attachment cap. A 4W. receptacle will be installed near a subpanel to provide power. Is a ground rod required?

Frank (cinkerf)

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#77492 06/15/01 11:43 AM
Joined: Feb 2001
Posts: 62
M
Member
Does the medical trailer have a panelboard?
If it does have a panelboard then I would consider it a structure. Which would lead to Article 250-32, etc., requiring a ground rod. If it doesn't, then I would consider the trailer as portable equipment. Which wouldn't require a ground rod.

[This message has been edited by Mike (edited 06-15-2001).]

#77493 06/15/01 12:37 PM
A
Anonymous
Unregistered
The metal shell of the trailer must throughly and solidly bonded to the EGC. You should test the resistance and find it to be low (<2 ohms). If it isn't bonded properly, then I see the need to get it correctly bonded. I don't see the need for a ground rod. A ground rod doesn't make a dangerous trailer safer.

I'm also assuming that the trailer will have a steel jack that would provide a path to earth if lightning strikes the trailer.
The trailer really should have metallic contact with the earth for lightning.

I'm assuming that the trailer has a panelboard - but I still consider it portable as evidenced by the fact that it will be rolled away after only 4 days.

#77494 06/15/01 04:24 PM
Joined: Oct 2000
Posts: 5,392
S
Member
hmmmm;
we need to become definitional here,

is this a structure ??

is this a mobile home???

is this a camper??

[Linked Image]

#77495 06/15/01 06:07 PM
Joined: Dec 2000
Posts: 84
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cinkerf Offline OP
Member
The Medical Trailor does have a panelboard.

Frank (cinkerf)

#77496 06/15/01 06:54 PM
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Anonymous
Unregistered
It's not a structure mainly because it is not erected on site. Yes, a camper could be a good comparison. But I suspect that no one cooks or sleeps in this trailer.

#77497 06/15/01 09:18 PM
Joined: Oct 2000
Posts: 5,392
S
Member
to G-rod or not to G-rod , that is the Q.
hmmm;

550-23(a), last sentence refers to 250-32, so does this mean only the disco gets the rod?

while we are on it, what about art 553 , floating buildings ???

#77498 06/18/01 07:41 AM
Joined: May 2001
Posts: 176
W
Member
I would consider the trailer as portable equipment since it has a cord and attachment plug. Even though the trailer was probably manufactured to the stringent standards of MHMA and other required standards (which by the way are now a lot stricter than they were twenty and thirty years ago when I bought my first mobile home).
The cord and plug have two phase conductors, a neutral and a ground. The receptacle supplying power to the unit is deemed as grounded and providing a ground return path. Having said all of that, I think I would insure the shell and frame are electrically connected to the ground in the cable. An ohmmeter check should suffice. If your meter is in the truck a couple of hundred feet away then a scrap piece of #10 connected to the frame and to the receptacle conduit should provide a suitable ground path for fault currents. A separate ground rod may set up a situation with circulating ground currents, and may cause additional problems.

#77499 06/18/01 09:19 AM
Joined: Feb 2001
Posts: 62
M
Member
Read the thread "Carnival Tent" in IAEI BB. It doesn't matter what NEC article we "think" the medical trailer falls under. It's the AHJ's interpretation that counts [Linked Image]


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