50 amp cheater

I am always confused about these adapters and I even have an electrical engineering degree, although I hated the power electrical class.

But, it seems to me that you have to make sure that the hot legs of the 30 amp and 20 amp circuits are out of phase with each other. Otherwise you would have the possibility of 50 amps on the neutral which would be fine for the motorhome and adapter, but I am not sure about the wiring in the electrical box.

Even worse would be using 2 30 amp plugs if both were in phase, which would then allow 60 amps on the neutral wire and overload all the wiring.

So, if someone can correct if I am wrong, I would appreciate it.

David

doxiemom11 wrote:
We have one and have used it at any campground that has a 30 amp plug. Ours is automatic and only boosts when it's needed. We are hooked up with one now and have used it all winter. We are running the water heater, frig and a 1500 watt heater (when it was cold) as our electric is included in our site rent. We do try not to overload though and do shut the frig off when using the convection oven or brew coffee. The cord on it is long enough that the actual device can sit inside a bay and is not visible. We purchased it when we were workamping for a summer and stuck on a 30 amp site that had low voltage and was causing problems. We couldn't run anything on electric, not even just 1 air conditioner. It worked there to solve the problem. Our unit was around $500

Your referring to a autoformer which is another useful device.

You're not wrong, but your first scenario of 50 amps on the neutral is within the design specs of the standard 50 amp 120/240 volt circuit used in motorhomes. The neutral is sized for the maximum 50 amps that would be seen if the entire 50 amp draw existed on one hot line, with zero draw on the other. An unlikely scenario at best, and one that also covers your second scenario, where 60 amps theoretically could be applied to the neutral, but in normal use is quite unlikely to occur. Even if it did occur, the safety margin of the wire rating would still handle the load.

dsteinman wrote:
I am always confused about these adapters and I even have an electrical engineering degree, although I hated the power electrical class.

But, it seems to me that you have to make sure that the hot legs of the 30 amp and 20 amp circuits are out of phase with each other. Otherwise you would have the possibility of 50 amps on the neutral which would be fine for the motorhome and adapter, but I am not sure about the wiring in the electrical box.

Even worse would be using 2 30 amp plugs if both were in phase, which would then allow 60 amps on the neutral wire and overload all the wiring.

So, if someone can correct if I am wrong, I would appreciate it.

David

Isn't a standard 50 amp plug using a total of 100 amps on the neutral with 50 amps on each leg?

dsteinman wrote:
I am always confused about these adapters and I even have an electrical engineering degree, although I hated the power electrical class.

But, it seems to me that you have to make sure that the hot legs of the 30 amp and 20 amp circuits are out of phase with each other. Otherwise you would have the possibility of 50 amps on the neutral which would be fine for the motorhome and adapter, but I am not sure about the wiring in the electrical box.

Even worse would be using 2 30 amp plugs if both were in phase, which would then allow 60 amps on the neutral wire and overload all the wiring.

So, if someone can correct if I am wrong, I would appreciate it.

David

60A would be more than the rated 50A but it's not likely to be a problem and most certainly not if it's not a sustained 60A draw.

The significant issue for a CG (even if they don't understand the details) is that this adapter connects the 2 neutrals together which in turn causes the current in each neutral to be based on the impedance of each wire. This means that the maximum amp draw on a given neutral is no longer limited by the CB on the corresponding hot line. It's possible for example with a 30-20 setup the 20A neutral could be carrying 30A. This applies to the cheater neutral and the pedestal neutral. Also this is much more likely to be a problem when both hots are on the same leg vs connected to split phase legs.

This is a neat pictorial showing the typical camp ground pedestal and where the 50A and 30A/15A/20A sources come from.



These two pictorial show the proper way to test each of the three 120VAC sources...

50AMP Service (TWO HOT leads from each side of the 240V feed)

You can see 240VAC here if you measure from HOT1 to HOT2. Some upscale RV trailers indeed use 240VAC for some of the Dryer setup. In the regular wired RV 50A trailer two Power Panel ZONEs are used to tap off only 120VAC from each HOT1 and HOT2 legs of the 240VAC.


30A/15-20A service (ONE HOT lead from the same side of the 120V feed)

The highest AC voltage you will see here is 120VAC. The only difference between the 30A Connection and the 15/20A connection would be the rating of the circuit breaker (30A-20A-15A)


My attempt of showing how it works
Roy Ken

rgatijnet1 wrote:
Isn't a standard 50 amp plug using a total of 100 amps on the neutral with 50 amps on each leg?

The neutral carries the difference of the current on the 2 hot legs not the sum.

It's a 240/120V single phase circuit just like a house except the house might have a 200A rating.

diveman52 wrote:
Your method scares the hell out of me!!!!

Why, Everything is protected by proper breakers, Everything is heavy enough all connections are good and solid there is no risk beyond that which originally existed. The design is soild.

The factory wiring in the motor home.. Not so good.. I have had to upgrade and/or replace parts of it, but this modification is over built for safety.

wa8yxm wrote:

diveman52 wrote:
Your method scares the hell out of me!!!!

Why, Everything is protected by proper breakers, Everything is heavy enough all connections are good and solid there is no risk beyond that which originally existed. The design is soild.

The factory wiring in the motor home.. Not so good.. I have had to upgrade and/or replace parts of it, but this modification is over built for safety.

At first glance it seems scary, but when you dig into what it is, it is actually quite safe. They are just emulating the way the RV is fed from the generator with two 120 volt feeds with one dedicated to the Air Conditioner. They are just breaking the AC lead and plugging it into 20 amp receptacle. In the OPs case he added a receptacle to plug in a heater.

We have a few State Parks in southern Georgia we visit which has 2, 30 amp plugs in the pedestal. My adapter has 2, 30 amp male ends which allows us to run the entire coach on electric without a low voltage issue.

I have tried to use it at some Florida SP that only have a 30 and 20 amp plug. It will trip the GFCI on the 20.

When we had our fiver with 30 amp line but 2 A/C units. I used an extension cord hooked to the 20 amp and a dedicated circuit to our bedroom A/C. It worked like a charm everywhere we went. I have a friend that unhooked one of his A/C units from his wired 50 amp service and dedicated its power through an extension cord to the available 20 amp to get around our southern heat with both A/C units working.