RV Park grounding

[jerjwillelec]

I am feeding seven (7) 125/250 volt 50 amp RV sites with two (2) 150 amp feeders from a single phase 400 amp service. I read 551.76(A) to say I must connect them all to the same grounding system as the Service rather than installing a rod at each site. Am I correct? Thanks, JW

 

[augie47]

Yes. Grounding of the equipmet at each RV site must be accomplished by an equipment grounding conductor run to the service equipment.
My opinon would be that if you wanted to add a ground rod at each site as a supplemental ground, you could do so, but that ground would not take the place of the required EGC to the service. See 250.4(A) 5 also

(ps: if I did my math correctly, your 150 amp feeders are slightly undersized)

 

[jerjwillelec]

I plan on feeding 3 sites with one 150 amp feeder and 4 sites with the other 150 amp feeder.

3 sites at 9600VA x 80% demand factor = 7680VA each / 240 volt = 96 amps
4 sites at 9600VA x 75% demand factor = 7200VA each / 240 volt = 120 amps

Is this not the correct calculation?

 

[augie47]

sorry JW, one day I will learn to read. I though it was 7 per breaker, which I believe puts you a tad over. You are correct on calculations.

 

[mistermudd]

Be a little careful although you do not need ground rods at each site, you do need to install a neutral that is not smaller then the ungrounded conductors. 2005 NEC 551.72 This is because of an unbalance that can be created by having several RVs plugged into the same leg of the 120/240v.

 

[jerjwillelec]

Yep, got it! Thanks