Evaluating new RV electrical setup

[Alaskansnowbirds]

IMHO if you haven't purchased this RV yet, I wouldn't walk, I would run away from it. I wouldn't buy anything that CW has touched. I assume this was done to install a second A/C. Instead of doing the job correctly, they jury-rigged the installation. I assume that to use both A/Cs you have to plug in two power cords. Just another example of CW's bad maintenance.

 

[msrdo]

So when you plug the 30 amp cord into shore power you get nothing but where exactly do you plug it in with the 50 amp adapter and get power, or how was the owner getting power that way? BTW a sniffer is not the best way to trace this out and you are likely to get false positives due to induced voltage

30A shore to "normal" 30A inlet... nothing. 30A cord connected to shore with a 30A/50A puck to 50A inlet provides power to the RV and the back (new) A/C unit. I'm assuming the previous owner could connect to a 50A shore pedestal. Wonder if the existing 30A RV wiring is OK for potential 50A draw? Could run a bit over 30A on the "RV" side of the inlet if lots was running... Microwave, hair dryer, A/C.. but would guess the RV 30 breaker would trip.

 

[msrdo]

IMHO if you haven't purchased this RV yet, I wouldn't walk, I would run away from it. I wouldn't buy anything that CW has touched. I assume this was done to install a second A/C. Instead of doing the job correctly, they jury-rigged the installation. I assume that to use both A/Cs you have to plug in two power cords. Just another example of CW's bad maintenance.

The wiring was done to accommodate the 2nd A/C. But only one cord, the 50A inlet. Not meaning to be snarky Don, but how should the install be done to be correct? Again, not trying to call you out..

 

[rvlifer]

The wiring was done to accommodate the 2nd A/C. But only one cord, the 50A inlet. Not meaning to be snarky Don, but how should the install be done to be correct? Again, not trying to call you out..

The entire service should be upgraded from 30a to 50a. Larger gauge wiring, higher amp circuit breakers etc.

would be a single 50a plug with 50a from shore power to the ac breaker box then 30a out to each ac unit

Might be othwr ways but that is how mine is wired

 

[rvlifer]

In that setup if you used an adapter to plug into 30a shore power both ac units would still start but would trip the 30a campground circuit breaker

 

[msrdo]

So when you plug the 30 amp cord into shore power you get nothing but where exactly do you plug it in with the 50 amp adapter and get power, or how was the owner getting power that way? BTW a sniffer is not the best way to trace this out and you are likely to get false positives due to induced voltage

See above. The 30A inlet is dead. The 50A inlet is in a storage bay that is behind the door accessing the city water hookup. I agree about the sniffer. But with power coming in from the 50A inlet, I get nothing backfed to the "normal" 30A inlet. Wondering if that wire is going to the 30a inlet. Sniffer would confirm current even if the inlet plug was disconnected. Hopefully can chase that wire tomorrow!

 

[msrdo]

In that setup if you used an adapter to plug into 30a shore power both ac units would still start but would trip the 30a campground circuit breaker

I suspect you are right.

 

[rvlifer]

Wonder if the existing 30A RV wiring is OK for potential 50A draw?

If the 30a wire was not upgraded to a larger gauge wire (10ga for 50a iirc), there would be more amps running over the wiring than it is rated for. The wire would overheat and could cause a fire. Bad news in an rv.

 

[rvlifer]

There are others here who know far more than i do about electrical stuff. Im sure they will reply soon and provide a more definitive answer. They are pros. I only know enough to be dangerous.

 

[Alaskansnowbirds]

The wiring was done to accommodate the 2nd A/C. But only one cord, the 50A inlet. Not meaning to be snarky Don, but how should the install be done to be correct? Again, not trying to call you out..

The RV should have been converted to a 50amp service.

Upgraded to a 50amp load center, proper sized wire (four conductor instead of three conductor) from load center to ATS. Rear A/C wired to load center. 15amp plug wired to load center. May also need a new ATS that can switch two hot legs. A 50amp cord from the ATS to the external pedestal. If you have access to a 50amp receptacle you shouldn't need to use any adapter pucks.

From your drawing, I would ASSUME (I have no idea what they did), that they disconnected the 30amp cord from the ATS and just didn't remove it. Again from your drawing, they wired one leg of the 50amp service to the rear A/C and the other leg of the 50amp service to the ATS -> load center.

So one leg of the 50amp service is only supplying power to the rear A/C and the other leg is supplying power to everything else in the RV. A very unbalanced setup.

 

[workinonit]

You said it has an EMS. I'm assuming it is on that 50A service that's not really a 50A service. What brand EMS is it? Is it happy when this thing is plugged in and what does it read with everything running. Hopefully it has auto shutoff. One question, what is a puck? A hockey puck in electrical terms is a transducer that converts some field value to a 4-20 mA signal in DCS controls. It resembles a hockey puck. Never heard of a puck in the terms you are using.

 

[Onyrlef]

You can determine the number of cows in a pasture by counting the legs and dividing by 4 or counting the heads. Leave the original 30 amp as is. Run a 20 amp pigtail for the new a/c. Buy a 50 amp dogbone w/ a 30 amp and 20 amp leg. Plug into 50 amp at the pedestal and it’s all good.

 

[workinonit]

The 30A is not connected according to his drawing.

 

[bigb56]

At first I was under the impression that one leg of the 50 served the original load center and the other leg went straight to the rear AC with some sort of 20 amp OCPD in the line and was possibly just a 12 gauge Romex, so I was concerned about a small gauge Romex connected to a 50 amp feed. I was also confused about all the mention of 30 amp and 50 amps cords, adapters and plug combinations. It didn't sound good.

Then, in post #16 we learned that there is a second panel containing the OCPD for the rear AC, and it was confirmed there is an inlet in post #22. This makes more sense and explains the 30 and 50 amp cords and adapter. The original 30 amp inlet and wiring is likely abandoned and capped off (if not, the 30 amp inlet would become energized by a backfeed when the new system was powered up) but is something I'd want to verify.

I do question how the new sub panel is fed, hopefully with at least #10 and not with #12.

If fed with #10, even though #10 is only rated for 30 amps, this would be the same as the original panel, where when using a 50 to 30 adapter, the 50 amp pedestal breaker protects the 30 amp cord and feeders from short circuit and the 30 amp main in the RV protects against overload. #12 wire will only have a #12 grounding conductor and the concern there is that it could possibly melt before the 50A breaker trips during a short circuit, while a #10 grounding conductor is rated to be used on circuits up to 60 amps.

I probably would have run the 50 amp directly into a panel in the bay (with a back fed main) and from there fed the rear AC and the existing system both from that panel with a 30 amp and a 20 amp breaker. That would have been a more conventional way to do things. But in actuality, if it is set up with correctly sized wires and enclosures it may be fine. I am not sure about all the legalities but there are plenty of legal sticks and bricks installations where conductors are protected in this manner, as well as user equipment where cords are smaller than the circuits they are plugged into.

Kudos to @Pedro Dog for looking through all the noise and confusion early on and seeing this for what it is, I'm a bit on the slow side sometimes.

 

[Kirk]

The wiring was done to accommodate the 2nd A/C. But only one cord, the 50A inlet

You have an obvious modification by a previous owner and doubtfully by an electrician. As a retired electromechanical service technician, there is no way that I would buy that RV without actually tracing all of that wire to see exactly what was done and how. Even then, I probably would not buy it.

 

[Gary RV_Wizard]

It's a factory 30A RV that's been converted to a 50A connector. The generator and ATS are 30A so that remains stock, including the load center (romex #1). The 2nd AC is a satellite independent unit that will not work on the generator (romex #2), only on the 50A "new" connector and cable to 50A pedestal. This looks to me like an OK way to do it. The two romex are just a way to split the neutral to 2 loads. If the workmanship is done right, I see no problem with it, it's actually pretty "elegant" as one of my engineering professors used to say.

I read it the same as Pedro Dog. It's a minimal and lower cost way to add a second AC and is workable. The full conversion to 50A as described by Don is the ideal solution, but that doesn't mean the minimal way is unacceptable or unsafe. The original 30A inlet is almost sure disconnected and irrelevant.

So when a 50A shore cord is used and plugged to a 50A pedestal outlet, there is 50A/120v available at the 30A ATS via one leg and another 50A/120v available to the rear a/c via the other leg. That's not an issue because the demand on those legs is limited by the breakers in the coach - 30A load center main and 20A for the 2nd a/c feeder.

But when the 50A shore cord is plugged to a 30A/120v pedestal outlet via a 50/30 adapter, the 30A source is split between the two 50A legs. You can get as much as 30A on either leg but the combined total can never exceed 30A. If you attempt to run the 2nd a/c, there will only be about 16-18 amps left for the rest of the coach and breaker trips on the pedestal 30A source are all but inevitable. However, if the rear a/c is simple left off (turn off the 20A breaker?), then the 30A load center can use the full 30A via one leg and will be fully functional.

 

[Gary RV_Wizard]

the other leg went straight to the rear AC with some sort of 20 amp OCPD in the line and was possibly just a 12 gauge Romex, so I was concerned about a small gauge Romex connected to a 50 amp feed

There is nothing wrong with a smaller wire connected to a large amp source as long as the smaller wire feeds only a low demand device. In fact, house wiring is normally just that way, e.g. a small appliance with a 16 or 18 gauge cord plugged to a 15A outlet fed by a 14 or 12 gauge wire. So that 50A (6 gauge) wire can't push 50A into the smaller wire because the load in the smaller wire is limited by the 20A breaker downstream.

 

[bigb56]

There is nothing wrong with a smaller wire connected to a large amp source as long as the smaller wire feeds only a low demand device. In fact, house wiring is normally just that way, e.g. a small appliance with a 16 or 18 gauge cord plugged to a 15A outlet fed by a 14 or 12 gauge wire. So that 50A (6 gauge) wire can't push 50A into the smaller wire because the load in the smaller wire is limited by the 20A breaker downstream.

I realize that and as I explained it in my earlier post the caveat is the short circuit protection. There are minimum wire sizes for tap conductors based on short circuit protection. Overcurrent can be controlled at the load end but not short circuit protection, that protection has to come from the supply side and the danger is an undersized conductor melting before the fault can clear, or damage to the smaller conductors. I am referring to the permanent conductors here, not secondary wiring like cords. If a cord gets shorted and blows in half you just replace it. A permanent conductor concealed in a wall is another matter and unknown damage can create a hazard.

There are specific rules for sizing tap conductors in the NEC. The only allowance I am familiar with that allows a #12 to tap a 50 amp circuit is Article 210.19 exception (C) which is reserved for cooking appliance circuits where two or more cooking appliances share a circuit up to 50 amps.

 

[No cats]

Is this what your concern is? The second AC has a 20 A CB so that section is protected. So the concern is that the wiring to that 20A CB shorts, the section to the 50A service could melt?

The original wiring 30A cable to the OEM can be argued has the same situation. But the OEM setup is fed with 50A when folks use adapters.

 

[rvlifer]

before i agreed to buy that rv i would hire an electrician to inspect it. If they told me it was up to code i might lean more toward buying it

That would be in addition to an nvria inspection