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Tuesday, June 21, 2016
Question:
Thanks for your insight into the NEC! We are designing the power distribution system to a number of chord and plug connected railroad cars that only have HVAC, lights, and a small amount of refrigeration as loads within the cars. There is no section in the Code that covers RR yards. There are sections 551 and 555 regarding RV parks and marinas. Why are the demand factors in Table 551.73(A) and Table 555.12 different for boats and RVs? A boat is just an RV that floats. If I had some insight as to why these are different, then I might be able to come up with acceptable demand factors for railroad cars parked in a RR yard.
Thanks! Robert Frye
A
Answer:
Hey Robert thanks for your question and the kind words. Railways installations are excluded from the NEC as stated in 90.2(B)(3) but they seem to be used for different purposes that what you are describing. Some boat owners might be offended that you referred to their yacht as an RV that floats but it is an interesting thought. Demand factors for RV parks and marinas are different based on their expected use supported by a history of load demands. You didn't say how the railroad cars will be used or how many there are so I would use Article 220 for calculating the load. If it will be a situation similar to an RV park you might convince the AHJ the demand factors in Table 551.73(A) are reasonable. If you can get those railroad cars to float please send a picture.