ElectricVehicle said:
TEG said:
Yes, RVer terminology is a bit weird. If they can plug a 20amp air-conditioner into one (120V) leg, and a 30amp air-conditioner into the other 120V leg then they call it "50 amp service" (20+30). I think a typical RV may only have 120V appliances, and even though they use a NEMA14-50 240V plug/socket it is really just a way to get two feeds of 120V.
That's not correct as I understand it. NEMA 14-50 is a 120/240V circuit that is rated at up to 50A for 120V or 240V applications.
I think the RVers use the 14-50 plug/socket in ways that aren't typical.
For instance, check out the "Dogbone" adapters:
http://www.google.com/products/catalog?hl=en&q=dogbone+adapter&bav=on.2,or.r_gc.r_pw.&um=1&ie=UTF-8&cid=1181167407191672565&sa=X&ei=vWm2TZnaPIfGsAOKpr2pAQ&ved=0CDEQ8wIwAg#
The way they state it you get "50 amp service from a 30 amp plug".
The RV terminology just seems to be "50 amp" means NEMA14-50, but they may only have one 120V leg active on the 14-50, and it may be fed by a 30 amp breaker on the other end.
Basically what I am saying is that when you see a cord with a NEMA14-50 on the end at a campground, don't assume it has 50amps of 240V available.
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http://www.rvtravel.com/publish/120-Volt_AC_Systems.shtml
...Campground hook-ups often have three receptacles: 20, 30 and 50 amps.
...This is because the 50-amp receptacle actually conducts two 120-volt circuits in order to supply the 50 amps that big rigs need.
In effect, it is a 240-volt receptacle, like those used for electric clothes dryers in a house.
RVs with two air conditioners need the 50-amp circuit in order to run both air conditioners at the same time, because each air conditioner runs on a separate 120-volt circuit.
...Adapters are available that will allow you to hook up your RV to any campground receptacle regardless of what type of plug is on the RV power cord. Of course, you are limited to the available amperage at the receptacle. A 20-amp receptacle will limit the number of appliances that can be run at the same time and may not be sufficient to run an air conditioner. An RV that has a 50-amp plug may find that only one air conditioner will operate if plugged into a 30-amp receptacle.
If your RV is connected to a receptacle that is higher than what is required (for example, when a 30-amp power cord with an adapter is plugged into a 50-amp receptacle), you must limit your electrical usage to 30 amps at any one time. Even though 50 amps are available, the main circuit breaker will trip if the RV is pulling more than 30 amps...