Electrical Load and Feeder Sizing for Three Planned RV Parks, Dayton, Strawn and San Antonio (2018-2021)

An RV park is a row of large, intermittent loads at the end of long underground runs. We sized the service or the feeders for three planned parks between 2018 and 2021, near Dayton, near Strawn and in San Antonio.

Dayton: will 200 A be enough?

The Dayton owner planned five sites with 50, 30 and 20 A combination receptacles, one site with 30 and 20 A receptacles, and a 30 A, 240 V septic system. The utility could offer at most a 200 A, 240 V single-phase service and asked for a study to confirm it was enough. Using NEC^® Articles 551 and 220, each 50 A site counts as 12,000 VA and the 30 A site as 3,600 VA, both at a demand factor of 0.6. With no nameplate data for the septic system, we counted its full breaker rating, 7,200 VA. The total came to 45.36 kVA, or 189 A, so the 200 A service will do. The 2018 letter also notes that any later addition must be checked again.

Strawn: answering the installer questions

For a park near Strawn in 2019, the owner asked general questions, and we answered them as tables. One feeder serving three RVs needs cable rated for 150 A; four RVs, 187.5 A; five, 203 A; six, 225 A, after demand factors from NEC Table 551.73(A) and a 1.25 factor. The matching cables run from 1/0 copper or 3/0 aluminum on a 150 A breaker up to 4/0 copper or 300 kcmil aluminum on 225 A, all 90 °C direct burial cable on terminations rated 75 °C or better, with separate circuits kept 24 inches apart and a 113 °F design ambient. For a 3% voltage drop, those feeders can run from about 310 to 480 feet. Longer runs need a boost transformer, or the utility can raise its transformer tap. Taps off a utility transformer are allowed under the tap rules, with up to six fused disconnects grouped on one rack within 10 feet of the transformer.

San Antonio: 70 sites and an office

The San Antonio plan in 2021 had 70 sites, each with a 50, 30 and 20 A pedestal, and a 24 by 24 foot office with a laundry room of two washers and two dryers. At 12 kVA per site and a demand factor of 0.41, the sites come to 344.4 kVA. We raised the office load to 40 kVA to cover commercial laundry, for a total of 384.4 kVA, and entered the values on the form the city uses.

Related services

Service and feeder sizing of this kind is described on our page for load analysis.