Portable electric heater in coach

[Kenneth Brewer]

Jim,

Your description of the rating of circuit breakers is true. But, nevertheless you may NOT put a 60A rated breaker on a 50A rated circuit, if that is what the circuit is rated (wire sizes enter in to the situation, among other things). Fault current/short circuit study evaluations are also a factor when sizing breakers, as well as whether or not ground or neutral might be involved, or whether we are talking a line breaker or load breaker. An electrical inspector that spots something like this
will fail the inspection, industrially or commercially. Equipment in question would have to be shut down immediately.

Inspectors can and do make mistakes that help or hurt owner/operators, and I can testify on this from over 40 years experience/exposure, but the code seems pretty clear here. By the way, the code with regard to cirbuit breaker rating is hotly contested (nothing new) whenever the NEC makes a revision. Whether or not something is a code violation is often argued, even by IEEE and/or NEC contributors, but I think this is an 'easy' one.

We need to be very careful when recommending electrical protection advice. The easiest way to stay out of trouble is to stay at or below current or voltage ratings.

Now I'm done on this one.

[Jon Wehrenberg]

Jim,

The 80% is no secret. It has been discussed here on this site numerous times.

Power management is a must on these coaches, and when we are on 50 amp service, we can do pretty much anything we need to do with little concern as long as we are aware that sustained power usage in excess of 40 amps per leg (or 24 amps total, or 16 amps total, depending on power source) may trip the breakers. The answer however is not to step up the breaker size because everything, including our power cords is sized for 50 amp service.

I want the breakers at the campground power outlet to trip long before I have a fire due to overloaded wires.

[truk4u]

Great answers from the electrical dudes in our group, I'm sticking to 12/24! As a practice, I always watch the amp loads and when they push into the high 30's on any leg, I start reducing loads.

Here's another teaser.... When running on gen, if the loads get real high on one leg and voltage starts down into the teens, the other leg voltage climbs to about 130 volt. The Liberty does this and also my CC did. I talked to Powertech about this and they said that is normal. Just curious why this happens.

[jello_jeep]

Because of the lack of un-obtainium used in the current breakers, outlawed by Al Gore in the 90's, as the manufacture of it caused the current global warming in the South.

Just curious why this happens.

[JIM CHALOUPKA]

OK, Jon and Ken. I am not disputing what you have said.
You have taken my statements out of context. I was answering specific implied questions by Truck.

I said, "Tom, I think, if you want 50A at the plug then you need a 60A breaker, min.. ( that means to me that if he wants 50A at the plug with common breakers he needs a line [properly sized] and with a 60A breaker min nothing more implied )
The distance your plug is from the service panel and the size of the wire to the plug also come into play." (that means to me check it out and we can discuss it if you want [had he come back with the wire size I would have suggested that it would determine the breaker size])

Other things that were not specifically discussed were voltage drop at the plug (due to the length of the run, and total watts required at the end of the run [the plug]. These values are unknown to me and I wanted Truck to know that they have an influence on his electric circuit.


From what I read in Truck's post I got that he asked for something (from his electrician) and did not know whether he got it or not. Truck was talking about a 100A panel with a 50A breaker and 25A on each leg and 29A load, well what does he have there. I meant that he could look at his wire size and if in fact he wanted 50A at the plug he should have a 60A breaker in the service panel min. and to check the wire size to the plug. (#6 THHN insulated copper wire will handle 70A ). If he only had (#10 THHN copper wire, which is good for 40A he should not even use a 50A breaker)

#6 wire and standard 50A breaker are used for a circuit that is commonly called a 50A circuit. You do not however have a circuit that will be rated 50A for a continuous draw of 50A.

I do not know what he had, has or wants. I was only trying to offer knowledge so he could decide for himself with what I mentioned, and a little discussion, which did not happen.

I did not say he should or must do anything.

I believe nothing I have said is incorrect.

JIM

[truk4u]

# 6 wire and I got my answer from my Electrician as previously posted.

Thanks for helping Jimmy C, I think you need a sunny Liberty vacation!

[JIM CHALOUPKA]

Your right about that Thomas, but it's not happening now.

JIM

[Jon Wehrenberg]

Jim, just think of 20, 30 or 50 amp as a nominal value, just like 12 volt batteries are not really 12 volts.

When sizing wires and components it is still based on breaker rating. You may not be able to get 50 amps continuous through a 50 amp breaker, but you still need #6 wire.