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Corky

In 2000 I bought a new 5th wheel with 50 amp service. there was a 50 amp breaker box in the front compartment. A 30 amp breaker fed the other breaker box on a 12 gage 20 amp wire which supplied the rest of the coach. A 15 amp breaker supplied the water heater and hair dryer. every time you showered and then tried to dry your hair the breaker tripped.
The other side of the 50 amp service on had the plug for the washing machine and 2nd air conditioner on it which I did not have.
I did a lot of rewiring to correct these problems.

Jim

Hi Chuck, hope you enjoy your visit in Hollister, I’ve found it a great place to live, stay awhile and check out the surrounding areas., Cheers!

LARRY MCGAUGH

Even though the receptacle found in your RV is rated at 120 VAC, the 50-amp shore power is actually a 120/240 VAC four wire service. The acronym VAC stands for “Volts of Alternating Current” which means the voltage is constantly changing from 0 volts up to 120 volts Positive back down to O volts, then it goes to negative 120 volts and then back up to 0 volts. This happens sixty times a second. This is commonly referred to as 120/240 VAC 60 HZ (Hertz).
The actual electricity that feeds your 120 VAC receptacle in your RV comes from your 120/240 VAC breaker panel. This panel is supplied with 240 VAC which is made of two 120 VAC legs that are 180 degrees out of phase. This means that when Leg-1 of the 120 VAC is going from 0 to 120 volts positive. Leg two of the 120 VAC is going from 0 to 120 volts negative.
To get 240 VAC for the larger appliances like a CheapHeat™ system, rather that going from one hot leg to neutral (120 VAC). Power is now taken from the two opposing hot legs and since they are 180 degrees out of phase, the end result is 240 VAC. Now that the neutral (white wire) isn’t used in the 240 VAC configuration.
Now let’s review the four wire 50-amp shore power cord, the cord we are talking about has four 6 gauge wires rated at 50-amps each. Which means the cord has two 50-amps legs at 120 VAC (Hot to Neutral) for a total of 100-amps at 120 VAC or one circuit of 240 VAC @ 50 amps (L-1 Hot to L-2 Hot), or a combination of the two.
Wait! If we have 120 VAC @ 50 amps on the Red to White and 120 VAC @ 50 amps on the Black to White, wouldn’t that be 120 VAC @100 amps on the White wire since there is only one white wire? No it won’t, because the two hot legs are 180 degrees out of phase. When Leg-1 electrons are moving towards Positive 120 volts the Leg-2 electrons are moving towards Negative 120 Volts. This means that when correctly wired (phased) the Neutral leg will see no electron flow, that’s why it’s called the Neutral Leg, thus no overload.
If the RV park pedestal isn’t wired correctly, and the two legs are not out of phase, you will have 100-amps applied to the white wire that is only rated for 50 amps. In that scenario you have both Leg 1 and 2 electrons moving towards 120 volts positive and then negative at the same time. Which means you have double the electron flow (Current) going through the white wire when it’s only rated for half that load. End result is an overloaded wire that will overheat and very possibly cause a fire.

******* DANGER ******* DANGER ******* DANGER *******

How do you know when you have an incorrectly wired Shore Power Pedestal? There are two simple ways, one is to install a surge protector that identifies incorrect phasing and locks out the power to the RV. The second way is to use a simple voltmeter that is rated to test AC voltage up to 300 volts. If the pedestal is wired correctly when you test from Leg-1 to Leg-2 (not Neutral) and the two legs are 180 degrees out of phase as they should be, the meter will read 240 VAC. When the Shore Power Pedestal is wired incorrectly, the two legs are at the same phase. Then the test from Leg-1 to Leg-2 (not Neutral) will read 0 volts on the meter. As stated previously, this is an unsafe condition because you can have a 100 Amp load on a wire that is only rated for 50-amps. All of that being said this means that using a 30-amp to 50-amp pigtail adapter will NOT allow you to see 240 VAC in your breaker panel. Because in that scenario your just splitting the same single black hot leg on the 30 amp plug to feed both the red and black on the 50 amp plug.
Its also important to note, that the CheapHeat™ Electric Hybrid Furnace kit is the only RV product that uses 240 VAC in an RV. It is designed to operate on a 50-amp service and it is not subject to these types of overload problems. Along with its inherent phase protection, it also has multiple high temperature safeties to protect from any overheat conditions. It is also hard wired directly into the main power system of the RV removing the potential fire hazard that can happen when plug in portable electric heaters are used.

Harry Salit

I read Mikes article about the difference between 20, 30 & 50 amps. He makes it sound like if you have 50 amps you can run everything!

I have 50 am service but if I run more than 20 amps on the one circuit that serves the kitchen, living room & bathroom the 20 amp breaker on the inverter trips. The micro, water heater and A/C are on their own circuits.
Strange way of wiring, so the 50 amps does me no good if I want to run the coffee maker, toaster oven, hair dryer, crock pot, etc at the same time….

Judy

Hi Chuck. I”ve enjoyed your newsletter for years. This week I learned two things from the Solo article. It suggested leaving id in the rv when hiking alone and also letting a neighbor know. I would love to read a weekly column for solo rv’ers! There are more of us out there than you might guess. Those tips were both invaluable. Thanks for your consideration. Judy