Using 50 amp for 30 amp system

RLS7201 wrote:
Maybe I should have been more specific. The 10 gauge, 30 amp cord is not protected properly. If the cord shorts out, then 50 amps can pass through the cord. That is an issue. That is before the RV 30 amp main breaker. Boom, bang, flash, fire!

Richard

The device is limited to 30 amps. And go ahead and short #10 wire into a 50 amp breaker... breaker will trip.
Although you are correct if a high resistance path develops there could be enough amps and heat to cause a fire. However this is also possible on the 30 amp supply so risk is similar.

Same condition exists for a common lamp at home with a 15a outlet and #18 cord.

DownTheAvenue wrote:
There may be an advantage. The 30 amp receptacle is most used and often is worn, so the plug fits loosely. This can cause a poor connection, arcing, and overheating of the plug. Using the less used 50 amp receptacle which is often in better shape, you may avoid the overheating situation.

I carry an adaptor for just-in-case. Had to use it a few months back at a site in Chippokes State Park, Virginia. The 30 amp receptacle was installed upside-down from the usual orientation. It caused my EMS to hang in the air where it's weight would pull the plug out of the box. Used the adaptor to connect to the normally-oriented 50 amp receptacle. It saved our trip because the park was sold out that weekend and we could not have changed sites.

RLS7201 wrote:

pianotuna wrote:
Hi Richard,

Plug in devices are not covered under NEC.

I have a "break out box" which I use. It contains one 30 amp female plug with a 30 amp breaker, and two 20 amp outlets, each with their own 20 amp breakers.

The #10 cord can't draw more than the 30 amps that the RV main breaker allows. That makes the question a "non issue".

RLS7201 wrote:
I find it interesting that your 10 gauge cord, from pedestal to coach main breaker, will be protected by a 50 amp breaker. Always wondered how that fits in the NEC.

Richard

Maybe I should have been more specific. The 10 gauge, 30 amp cord is not protected properly. If the cord shorts out, then 50 amps can pass through the cord. That is an issue. That is before the RV 30 amp main breaker. Boom, bang, flash, fire!

Richard

As mentioned earlier, how is that any different than all the light 18-20ga zip cord connecting lamps, clocks, etc. to 15/20 amp outlets in your home? Or that 16ga extension cord you use outside to connect the hedge trimmer, etc. to a 15/20 amp outlet? An RV is basically just a large "portable appliance", although it does receive special attention in the NEC for the dual voltage systems, etc.

wa8yxm wrote:

and in all cases.. There is a very slight "power loss" in the cord, this slight difference means that you are more likely to trip the park's 30 amp breaker than the one in your RV. Plus the park's likely has been abused more and may only be a 25 amp now days (or less).

There is a slight power loss in the cord, but it's a voltage drop and not a loss of current. Since circuit breakers are designed to react to current, not to power, the power loss in the cord does not make the pedestal breaker more likely to trip than the RV breaker.

If you have some electrical device that connects across the leads and consumes power between the inlet and the main breaker, such as an EMS unit, the power that it consumes would lead to additional current at the pedestal breaker vs. the RV main breaker. A wire alone doesn't do that.

In actual operation for moderate overloads or near-overloads, most common circuit breakers actually work as thermal devices (they detect current by the heating of an internal bimetallic strip or something similar) and so the breaker that's in the warmer environment and/or more thoroughly enclosed so as to dissipate less heat would be more likely to trip first, all other things being equal.

427435 wrote:
I'm thinking that there might be less voltage drop in an under wired park..........................

But it might work out the other way too.

I suggest:
Try the 30 first. If the plug is tight and your voltage monitor shows good (you do have one, right?) then keep the adapter for when the 30 connection really has a problem.

Hi Richard,

Your unlikely scenario is why I have a 50 to 30 and dual 20 amp break out box with circuit breakers.

A greater issue is that the adapters for 50 place the entire load on one leg. Not so great if 8 30 amp rv's plug in--and one 50 amp rv plugs in. They may find one leg at low voltage and the neutral may not be balanced.

pianotuna wrote:
Hi Richard,

Plug in devices are not covered under NEC.

I have a "break out box" which I use. It contains one 30 amp female plug with a 30 amp breaker, and two 20 amp outlets, each with their own 20 amp breakers.

The #10 cord can't draw more than the 30 amps that the RV main breaker allows. That makes the question a "non issue".

RLS7201 wrote:
I find it interesting that your 10 gauge cord, from pedestal to coach main breaker, will be protected by a 50 amp breaker. Always wondered how that fits in the NEC.

Richard

Maybe I should have been more specific. The 10 gauge, 30 amp cord is not protected properly. If the cord shorts out, then 50 amps can pass through the cord. That is an issue. That is before the RV 30 amp main breaker. Boom, bang, flash, fire!

Richard

427435 wrote:
We only only have a 30 amp system in our MH, but I've bought an adapter when only a 50 amp connection is available in a park. Would there be any advantage to using the adapter and a 50 amp connection even if the 30 amp connection were available?? I'm thinking that there might be less voltage drop in an under wired park..........................

In theory: NO
IN practice: Often yes.

IN some parks the 50 amp service is newer than the 30, and the 50 amp outlets are generally in better shape.

and in all cases.. There is a very slight "power loss" in the cord, this slight difference means that you are more likely to trip the park's 30 amp breaker than the one in your RV. Plus the park's likely has been abused more and may only be a 25 amp now days (or less).

Plugging into the 50 means if you try to draw say 40 amps. it's the breaker in your RV that will trip. so you do not have to get dressed and go outside to reset it in the middle of a downpour rain. (Seems it always trips during a downpour).

RLS7201 wrote:
I find it interesting that your 10 gauge cord, from pedestal to coach main breaker, will be protected by a 50 amp breaker. Always wondered how that fits in the NEC.

Richard

It's fine. Check around your home. How many of the cords on your lamps, TV, clocks, etc. are 18 or 16 AWG but they're plugged into 15 or 20 amp circuits. I don't think I have any cords on any of my tools or appliances that are actually #14 or #12 wire except possibly my air compressor.

Hi Richard,

Plug in devices are not covered under NEC.

I have a "break out box" which I use. It contains one 30 amp female plug with a 30 amp breaker, and two 20 amp outlets, each with their own 20 amp breakers.

The #10 cord can't draw more than the 30 amps that the RV main breaker allows. That makes the question a "non issue".

RLS7201 wrote:
I find it interesting that your 10 gauge cord, from pedestal to coach main breaker, will be protected by a 50 amp breaker. Always wondered how that fits in the NEC.

Richard