Marina calculated load vs demand factors

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Jon M

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I am reviewing a marina project and notice that the engineer is counting the total number of recetacles for demand factors. A pedestal has 1 30 amp and 1 50 amp receptacle per side. Table 555.12, Note 1, allows for the counting of the larger of the two receptacles for when calculating load. It just seems a bit off to use 4 receptacles toward the demand factor but only 2 for the calculated load. Is it right to allow the best of both worlds? Any thoughts would be appreciated. Haven't seen this concept addressed anywhere.
 
Interesting question. Let me see if I understand it correctly. Let?s say you have 10 slips, each with a 30 amp (125V) receptacle and a 50 amp (250V) receptacle. I ignore the 30 amp receptacles, and count the load as 10 times 50 times 240 volts, and get 120 KVA. I would then apply a demand factor (from Table 555.12) of 80% (for 10 receptacles), and get 96 KVA. Are you saying that the engineer is applying a demand factor of 70% (for 20 receptacles), and getting a result of 84 KVA?

If that is the concept that you are asking about, I would say that the engineer is wrong. Regrettably, the text of the article that tells you to use that table is not as clear as one could wish. Neither is the table itself. But I believe that as an inspection authority, you can make the call that the number of receptacles used to calculate the load and the number of receptacles used to determine the demand factor have to be the same.

Welcome to the forum.
 
charlie b said:
... But I believe that as an inspection authority, you can make the call that the number of receptacles used to calculate the load and the number of receptacles used to determine the demand factor have to be the same.

Welcome to the forum.
Click to expand...
Ditto.... twice over :thumbsup:
 
Yes, that is what the engineer is attempting to do. He is counting every receptacle on all the pedestals fed by a common feeder to take advantage of the lower demand factor, but only using the principle in Note 1 of Table 555.12 to use the larger receptacle for calculated load purposes. I don't believe this meets the intent of the section, but I heartily agree that the wording leaves room for interpretation. The scenario just doesn't seem right to me, so I was hoping that a consensus of opionion would be apparent :)
 
Agreed. I've encountered some engineers that don't know about article 555 when it comes to marina load calcs.
 
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