RV Calculation

[npazdernik]

At an RV site I want to set a 200 amp service how many sites can I hit off of that service. Can I load it up to 200 amps on the main or am I limited to 160 amps?



Here is what I was thinking of doing let me know if its OK

One line diagram

200 amp 30 circuit panel (weather proof)

3, 125-amp DP breakers each feeding 3- 50/30/20 rv peds with #1/0,#1/0,#1/0,#2 AL Conductors

Service Calculations
9600va x .55 demand factor = 5280va

5280 X 9 sites = 47520va
47520va / 240v = 198 amps

Branch Circuit Calc.
9600va x .8 demand factor = 7680va
7680va x 3 sites = 23,040va
23040va / 240v = 96 amps
96 A x 1.25 = 120 A fused at 125

OR

If I can only go to 160-amps on main service then I only get 7 sites spread out on 3 circuits??

 

[wbdvt]

Is there a reason that you are only doing 30A services to the RV sites? RV's come with either 30A or 50A requirements depending on size and mainly number of Air Conditioning units and some have residential refrigerators and washer/dryers.

 

[Smart $]

RV parks not my thing, so just to make certain, each pedestal is MLO with 50A, 30A, and 20A breakers for the respective receptacles?

The 125A circuits are feeders, not branch circuits and connection to each pedestal must be compliant with 240.21(B) if conductor size is reduced anywhere in the connection scheme. Also, the 125% factoring for continuous load in your "branch circuit" calculation is not mandated anywhere. If it were, you'd be required to escalate it up to your service determination, which answers both of your questions, the last by default.

 

[kwired]

Instead of messing with the panelboard and multiple feeders, why not just use 200 amp RV pedestals and run one 200 amp feeder to all of them?

Did not double check your math or demand factors for accuracy but if they are right just one 200 amp feed and up to 9 pedestals.

Been a while since I did one of those but seems about the same ballpark of what I recall putting on a 200 amp feed.

 

[cpinetree]

2011 NEC 551.73 for calculated load
Table 551.73(A) lists a demand factor of 55% for 9 sites

I think 551.73(C) allows the use of the demand for all 9 sites regardless of how you feed them for calculating the service entrance.

I am not sure, but I believe (Hopefully someone more knowledgeable will chime in) that is considered a continuous load so a 200amp service will not be sufficient.

198 x 120% = 237amps 250amp service minimum

You would then use the 80% demand for each 3 site feeder for wire size and breaker size of each of the groups of 3. (I think you have it as branch circuit calc in your original post)

 

[kwired]

2011 NEC 551.73 for calculated load
Table 551.73(A) lists a demand factor of 55% for 9 sites

I think 551.73(C) allows the use of the demand for all 9 sites regardless of how you feed them for calculating the service entrance.

I am not sure, but I believe (Hopefully someone more knowledgeable will chime in) that is considered a continuous load so a 200amp service will not be sufficient.

198 x 120% = 237amps 250amp service minimum

You would then use the 80% demand for each 3 site feeder for wire size and breaker size of each of the groups of 3. (I think you have it as branch circuit calc in your original post)

Demand factors exist when studies show that the load is not ordinarily continuous in specific situations. If the load is continuous there should be no need to apply a demand factor, I think. That still might mean you have continuous loads at the branch circuit level though.

 

[Smart $]

Demand factors exist when studies show that the load is not ordinarily continuous in specific situations. If the load is continuous there should be no need to apply a demand factor, I think. That still might mean you have continuous loads at the branch circuit level though.

There's a good chance there will be some continuous loads, but Code does not require calculating unknown loads as continuous, suspected or not. Specifying a minimum calculated load per receptacle is adjunctive to specifying demand factors... IMO.

 

[kwired]

There's a good chance there will be some continuous loads, but Code does not require calculating unknown loads as continuous, suspected or not. Specifying a minimum calculated load per receptacle is adjunctive to specifying demand factors... IMO.

I wasn't quite sure how to explain what I was thinking before, but this mostly compliments my line of thinking on why it isn't a continuous load. Thanks.