Recreational vehicle park

[tacomafc]

A recreational vehicle park has 20 sites. The sites are equipped with 20-ampere and 30-ampere supply facilities. The service will also consist of a building that will have a computed load of 90 amperes. The minimum feeder ampacity for the service conductors are:

3600va x 20 = 72,000 va x 45% (demand) =32,400 va / 240 volt = 135 amps + 90=225amp
The answer should be 279 amperes. what am i doing wrong? I also tried 125% of 90 amps but still no luck.

PLEASE HELP
thank you,
tacomafc

 

[augie47]

I tried to approach it that 5% of all RV sites had to have a 50 amp supply, (555.71) so I tried adding one 50 amp with (20) 30 amp, also tried adding two 50's with (20) 30's, also tried reducing the 30s by the # of 50's.
Still could not get 279.
Perhaos someone will teach both of us something

 

[tacomafc]

its has somthing to do with adding the 90 amps.

 

[jgunnels]

(try this )Recreational vehicle park

(try this )Recreational vehicle park

Just Learned how to do this several weeks ago.... I came up with 279amps.

first of all you have to take 20% (551.71 ) of the 20 sites at 9600va ( 4 )

then 70 % (551.71 ) of the 20 sites at 3600va ( 14 )

and the remainder (551.71 ) at 2400va ( 6 )

so what you end up doing is
4 x 9600 = 38,400
10 x 3600 = 36,000
6 x 2400 = 14,400
-------
88,800va / 240 volt then take 45% of this = 166.5amps ( 551.73 )
112.5
-------------
then add 125% of 90=112.5 amp 279.0 amps

hope this helps

 

[jgunnels]

forgot to mention you count the first four of the 3600va in the 9600va
this is how you get the 10 x 3600va not 14 x 3600va
basicly it is implied that the first ( 4 ) 3600va are in the 9600va
hope i didn't confuse it more then it already is.