ECN Forum Forums Code Related Discussion NEC & other Code issues Medical Trailor

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)

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).]

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.

hmmmm;
we need to become definitional here,

is this a structure ??

is this a mobile home???

is this a camper??

The Medical Trailor does have a panelboard.

Frank (cinkerf)

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.

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 ???

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.

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