capsfloyd wrote:
We are looking at a 50 amp TT.
It may help to know that it can be really hard to find 50 amp pedestals due to the min. NEC electrical requirements. RV manufacturers will entice folks to buy a 50 amp RV so you can run multiple AC units and also have more power for other loads, but they never tell you how hard it can be to find 50 amps.
In the 2005 edition of the NEC, 20 percent of an "RV park" (as the NEC calls them) were required to be 50 amps, and in prior to that edition, only 5 percent was required. Some private and some gov't CGs *may* have gone above the min. code requirement and provided more 50 amp pedestals and some may have done an upgrade to their wiring system. You might be able to be more selective in choosing a CG by researching in advance, but if you're on a road trip you may not have much of a choice.
We've stayed in several casino RV parks and all pedestals had 30 & 50 amp receptacles. Have been in some older CGs with no 50 amp pedestals at all. I've seen countless numbers of 50 amp RVs plugged into 30 amps with an adapter in many of the CGs we've been to. A 50 amp RV may sound great, but it would be good to be prepared to only find 30 amps in many CGs.
In addition, due to the way the NEC provides for min. "demand factors" and the required min. wiring size to a run of pedestals on the same feeder cable, voltage drop in a CG can be mild to severe due to demand factor allowances. If you have a 50 amp RV, there's not much you can do except for perhaps trying to be closer to the source of power (either a transformer or distribution panel).
Low voltage is simply very common out there and it's not normally a CG's fault. Having an autoformer is a really good idea. AC units especially are susceptible to low voltage (below 105 volts).
Interestingly, I just came across this statement from those responsible for NEC rule changes for 2005:
Text revised to increase the number of 50A, 125/250V receptacle recreational vehicle sites from 5 percent to 20 percent. This change was based on a survey of 500 campgrounds involving 45,000 recreational vehicle sites, which showed that an average of 18 percent of the sites provide 50A 125/250V receptacles. Seems to me that they should have assessed the numbers of 50 amp RVs being purchased at that time and projections for the future.
