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Thread: 50 amp.... Why so big?
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04-18-2021, 07:38 AM #51
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My work here is now done!
When I worked in a Steel Mill as an Electrician, I actually wore my hard hat with an Orange/Black safety sticker on it. The left side had the AC = Always confused....and the right side had the DC = D@mned Confused. It was good for a few laughs for sure.Last edited by xrated; 04-18-2021 at 07:42 AM.
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04-18-2021, 02:37 PM #52
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04-18-2021, 03:42 PM #53
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@xrated.
Thank you for your contribution to this forum regarding electrons. You always answer questions regarding electrical clearly and accurately.
JerryJerry & Linda
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04-18-2021, 04:56 PM #54
All the fun aside, the question of why there is nothing between a 30 amp service and a split phase 50 amp service is a good one. You either have a 30 amp or two 50s, total of 100 amp. The cable for a split phase 50 is pretty big, kinda like wrestling with a boa constrictor or anaconda.
I have seen a park where they posted 50 amp service is not split phase, a 240V dryer will not work. The neutral in the pedestal may be OK as it is likely separate circuits, the neutral in the cable may be undersized a tad.Judy & Larry
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04-18-2021, 08:10 PM #55
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04-18-2021, 09:07 PM #56
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04-18-2021, 09:38 PM #57
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OK, PLEASE READ XRATED’S POST #10 IN THIS THREAD FOR A VERY CLEAR EXPLANATION ABOUT 50A RV SUPPLY VOLTAGE.
An RV 50 amp plug is connected to a NEMA 14-50R receptacle. The same receptacle that I plug my 50 amp 240v electric car into. In fact it’s the exact same receptacle that my house 240v electric stove is plugged into. That plug supplies 240 volts to my Electric car charger and to my house electric stove heating elements between L1 and L2.
An RV separates L1 and L2 in the RV power distribution box into 2 separate 120 v legs, each capable of 50 amps each. If you measure between L1 and L2 at the receptacle you WILL measure 240 volts. If you measure between L1 and neutral or between L2 and neutral you will measure 120 v each.
Now a 30 amp RV TT-30R receptacle IS ONLY 120v with a single hot leg, a neutral and a ground. Occasionally an uninformed installer will unwittingly wire that as a 240v with 2 hot legs instead of 120v with a single hot leg.
Here’s a diagram of a 14-50R. Notice that there is 240v between the X and Y terminal.
Last edited by Jerryr; 04-19-2021 at 12:27 PM. Reason: Corrected NEMA typo
Jerry & Linda
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04-19-2021, 04:01 AM #58
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04-19-2021, 04:44 AM #59
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That is exactly the point of my original post. First, there is often confusion with terminology. The terms 30A and 50A are used a little too casually I think. The way those terms are used in the RV world implies that other than ampacity the two supplies are the same. We know from this discussion that 30A and 50A supplies are very different.
Your point about 80% of ampacity is well taken. I won't speak to electrical codes, but I think my understanding of how this works is pretty sound. It is true that the requirement to supply the 50A split phase outlet is 6 gauge wire. However, that wire can be downsized on the appliance side of that outlet. If you consider the RV to be the appliance and limit the current within the RV, the wire from the pedestal to the RV can be downsized.
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04-19-2021, 05:15 AM #60
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To the original question, why 50amps? You have to "size" for all the bling rv manufacturers have added to trailers.
I'm with you, 30a is lots. I'm usually on 15a. If I was full timing or at least months at a time, I would likely appreciate the 50.
@xrated , good explanation. I missed the teeter totter analogy but I know what you were trying to explain. Kind of wish I'd seen it.
Understanding Electricity without a good grounding in fundamentals is difficult.
Like we say at work..."electricity is a strange animal"
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