RV park pedestals

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wireman3736

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Vermont/Mass.
I'm going to be getting involved in an RV project in the spring that was partially done by another electrician, One section was already done and I see they fed them with 3 wire but some they pulled a separate bare copper ground wire with the three insulated aluminum conductors, also I don't see any ground rods at the pedestals. I have read the code but I'm still a little confused on the grounding,

1st do you have to use 4 wire, 2nd does the equipment ground have to be insulated, 3rd am I required to drive ground rods and 4th if I drive ground rods am I required to use a grounding conductor from the main panel or can I use 3 conductor then bond my ground and neutral at the pedestal per 250.32 (b) 2. My opinion is that I have to use 4 wire all insulated and I am required to install a GES at each pedestal. Seeing what others have done here though I want to have my facts straight when I talk to the park owner.

Looking for opinions.:-?
 
I believe that 551.7 specifies an equipment grounding conductor, and doesn't allow you to use the neutral to ground the pedestals. Idon't find a requirement for a ground rod at the pedestals.

Jim T
 
I believe you need 4 wire--art. 551.76(C) Neutral conductor not to be used as an equip. ground. I don't believe it needs to be an insulated ground

Art. 551.75 All elect. equip to be grounded as req. by art 250.
 
I've thought about this a little more and believe as long as the cord going to the RV is 4 wire then three wire with a GES at the pedestal meets the requirements.

Pedestal is a seperate structure IMO
 
I know in a mobile home park I've never had a problem with an inspector where the meter was more then 30' away so I add a disconnect within 30' with three wire and a GES at the stanchion, IMO same situation.
 
wireman3736 said:
I've thought about this a little more and believe as long as the cord going to the RV is 4 wire then three wire with a GES at the pedestal meets the requirements.
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You need to look at Part VII of 551 more carefully.

You can not use the neutral as a grounding means for the trailer or the pedestal.

You must run an EGC.


Do the job right or....
 
I read 551.76(D) and it says you cannot connect the grounding electrode to the neutral on the load side of the service disconnect, but then list a couple of exceptions with one being 250.32(B) (2) for separate structures.
 
iwire said:
You need to look at Part VII of 551 more carefully.
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I don't really see a part VII.

VI, maybe? That's for RV parks, which does seem to be what this question is about. If there's not more than 2 hookups, that section might not apply (I think).
 
Sorry I said part VII, my mistake.

What I see now that I have actually gotten my book out is this.

551.76(A) which requires exposed non current carrying metal parts to be connected back to the service or transformer via an EGC and as Dennis pointed out 551.76(C).
 
My mistake in Reading 551.76 (D) was that the wording does not include the word structure, it only says building. I agree that 4 wire is required for a 125/250 hook up. So now since it doesn't include the word structure I would assume that a GES is not required at the pedestal.
 
wireman3736 said:
. So now since it doesn't include the word structure I would assume that a GES is not required at the pedestal.
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Interesting....

There are 2 types of RV pedestals. Direct buried and pad mounted. I would call the pad mounted variety a structure.
 
Dennis Alwon said:
Structure-- Definition that which is built or constructed. Not sure the pedestal or pad mount would qualify.
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I agree, that it could be a grey area. On the other hand, I see no reason why you should not drive a ground rod there also and connect it to the ECG buss. It may or may not ever be of any benefit. Maybe while an RV is plugged in, with the TV antenna up, in a thunderstorm.
 
Driving rods for a couple of sites wouldn't add much to the job but 40-50 sites, driving two rods for each site could increase the cost by quit a bit, I guess the best way to find out if there required is to ask the AHJ, :)
 
wireman3736 said:
Driving rods for a couple of sites wouldn't add much to the job but 40-50 sites, driving two rods for each site could increase the cost by quit a bit, I guess the best way to find out if there required is to ask the AHJ, :)
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Right! You ask, "I don't need ground rods at each pedestal, do I?", while you're shaking your head 'no'. :grin:
 
What I see with three wire distribution rather than four wire is the loss of neutral at some point along the run, as some camper in bare feet holding onto the metallic handhold of his RV decends the stairs of said RV placing that bare foot on the ground...

I'd also suggest (despite the work involved) that ground rods are a great idea, to try and maintain an equipotential place where people in bare feet walk, in addition to the reasons already outlined by mdshunk above.
 
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