wesley1
Member
- Location
- Port St. Joe, Florida
- Occupation
- Electrical contractor owner
I have recently been asked to caculate how many 50 amp/ 250 volt shore power receptacles can be added to an existing 600 amp/ 240 volt panel at a local marina.The panel currently has 28 30 amp/ 125 volt shore power receptacles fed from this panel. I found in article 555 that the total load can be derated 70% and if I add the new receptacles a 60% derating can be done.My question is the table 555.12 says ( the sum of the rating of the receptacle). When figuring feeder caculations in article 220 the loads are figured as kva or kw. Do I simply add the amp rating of all receptacles and derate by 70% or do I change the 30amp rec to 125voltsX30 amps=3,750w then multiply by the 28 rec = 105,000w, then derate by 70% =73,500w, on a 240 volt feeder this =306.25 amps.since starting my company I have had very little experience with marinas and definetely want to get it right so breakers are not tripping this 4TH of July when the docks are full.Any help would be appreciated!