Hi Mike,
I have a 50-amp shore power plug on my fifth wheel camper and was told by the camping store that I needed to buy a 6300-watt Yamaha inverter generator. The generator has a 120/240 30-amp twist-lock plug as well as a 120-volt/30-amp twist-lock plug.
I have 2 AC units that I need to run in the summer when operating off the generator but I’m not sure how to do it and the camping store is now giving me the runaround. Attached is a picture of the outlets I have on my generator as well as an adapter plug I already own. I’m pretty good with 12-volt systems but not 120/240 volts.
Any help would be greatly appreciated. Thanks. —Jimmy
Jimmy,
Well, it’s a real shame that the camping store that sold you the generator can’t tell you how to hook it up to your RV. But let’s see what I can do to help.
If you look at the generator you’ll see both 20-amp and 30-amp outlets marked as 120-volts. So that part seems pretty straightforward. The 20-amp Edison outlet is just like you would find in your house. And the 30-amp/120-volt twist-lock outlet just needs a generator twist-lock to RV TT-30 outlet adapter to work with an RV’s 30-amp shore power plug. But the adapter plug you’ve already bought is NOT want you need to hook your 50-amp RV shore power plug into the generator. It’s really designed to hook your 50-amp plug into both a 20-amp and 30-amp outlet on a pedestal that doesn’t have a 50-amp outlet. However, that probably won’t work with any modern pedestal that has a GFCI on the 20-amp outlet because the current imbalance will probably cause the GFCI to trip.
What you really want to get is a 120/240-volt by 30-amp twist-lock to 120/240-volt by 50-amp outlet, which is commonly called a NEMA 14-50 or Stove Outlet. See photo right.
Now all you have to do is flip the switch on the generator to 120/240 volts, plug this adapter into the 120/240-volt twist-lock outlet, plug your 50-amp shore power plug into the adapter, and you’re in business. Remember, your 50-amp shore plug really doesn’t use any 240-volt power. It actually uses two separate hot lines with 50-amps each, for a total of 100 amps of current. However, your generator will only produce 30-amperes of current per leg, which adds up to 60 amps total. But that amount of current should be sufficient to run BOTH of your air conditioners at the same time as well as a bunch of other appliances.
Let’s play safe out there….
Mike Sokol is an electrical and professional sound expert with 40 years in the industry. Visit NoShockZone.org for more electrical safety tips. His excellent book RV Electrical Safety is available at Amazon.com. For more info on Mike’s qualifications as an electrical expert, click here.
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