30 Amp or 50 Amp?

[turk123]

Add a 50 amp. You can use the 50 when you get your electric Tesla auto. That's what I did.

The 30 amp comes off one leg of the 50 amp 220 plug. Buy the correct adapter. That's why it is only 120 volt. Why it's not 25 amp is quite odd, but I'm not an electrician.

Still worried, buy a good surge protector for the trailer that will mount near the 50 amp adapter. EMS PT30C

[TG Twinkie]

It is 50 amp on each hot leg. That's why it isn't 25 amp. There are 2 legs, a neutral and ground on 50 amp service.
The 30 amp adaptor uses 1leg, the neutral and the ground therefor when you use the 50 amp source there is 50 amps of power (6000 watts) available on that leg, but your adaptor is only good for 30 amps (3600 watts).

[VaTravelers]

Originally Posted by turk123

Add a 50 amp. You can use the 50 when you get your electric Tesla auto. That's what I did.

The 30 amp comes off one leg of the 50 amp 220 plug. Buy the correct adapter. That's why it is only 120 volt. Why it's not 25 amp is quite odd, but I'm not an electrician.

Still worried, buy a good surge protector for the trailer that will mount near the 50 amp adapter. EMS PT30C

Is the EMS PT30C weather proof?

[cwf]

Install 50... Wire properly (not 220!!!) use an "adapter" or buy A 50 AMP cord with A properly configured Airstream already attached!!!!

I like mine for the Airstream 50 amps.. Can prep for launch in he AC! I can also use the outlet to run my 110vac welder!!!! There are other reasons... I think you can figure those out!

[AstroBruce]

Originally Posted by cwf

Install 50... Wire properly (not 220!!!) use an "adapter" or buy A 50 AMP cord with A properly configured Airstream already attached!!!!

If not 220, then what?

Bruce

[Silverflames]

Originally Posted by TG Twinkie

If you install the system correctly you will have a sub panel with a 20amp, a 30amp and a 50amp breaker along with the appropriate receptacles matching the breakers.
If you have a coach which requires a 30 amp service you plug into the 30 amp receptacle and turn on the associated breaker.
Unless you have a coach with 2 air conditioners I doubt it will require more than a 30 amp service.
Do it once and do it right!

This will cost a bit more, but I believe this is the best route to go. It will also give you other wiring options as needed in the future.

[m.hony]

I just have a 50 amp receptacle on the front of my house because I have a 50 amp trailer.
There are other 15 or 20 amp receptacles on the house.
I chose the location based on where a water hydrant and sewer clean out are located.


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[cwf]

Originally Posted by AstroBruce

If not 220, then what?

Bruce

Bruce, to achieve 220/240 you use opposite phases "power legs" as we call them down in the swamp..

Here is a more professional but easy reading explanation.. I ignore the math...as it is not necessary for your question.

http://www.allaboutcircuits.com/text...power-systems/

[AstroBruce]

Originally Posted by cwf

Bruce, to achieve 220/240 you use opposite phases "power legs" as we call them down in the swamp..

Here is a more professional but easy reading explanation.. I ignore the math...as it is not necessary for your question.

http://www.allaboutcircuits.com/text...power-systems/

A 50 amp RV socket is wired with a 220/240 branch. Each leg is 120 volts. You said not to wire it with 220 volts. Why not? That is my question.

Bruce

[AtomicNo13]

The way you get 220 is to omit the neutral and wire across l1 and l2. Otherwise its simply 2 110 volt legs sharing a heavier common neutral.

[markdoane]

Originally Posted by AtomicNo13

The way you get 220 is to omit the neutral and wire across l1 and l2. Otherwise its simply 2 110 volt legs sharing a heavier common neutral.

Why would it need a heavier neutral? You can use a neutral the same size as one of the hot legs.

The proper term for split phase power is 120/240 VAC, not 220/240.

[TG Twinkie]

Because the neutral carries the accumulative current of both legs when used for 120 volt devices.

[rmkrum]

Uh, not quite.

The neutral carries the difference in current between the hot legs of a 220 circuit. If there is exactly zero current in one hot leg it's the worst case, and the full current is in the neutral. That's why NEC says it only needs to be the same size as the hot legs.

The phasing between the two hot leads is 180 degrees out. That's why this works.

This is why I was the go-to engineer on power distribution issues in our labs. Done this before, more than once. 50 amp connection is actually 220 volt with a neutral and safety ground (safety earth). That's why it's 4 wires. That's also why you need to be darn sure the neutral is properly connected. If it's not, serious issues ensue.

Lew? Amiright?


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[J. Morgan]

You are right.


Gradiens super tenui glacie.

[J. Morgan]

But your answer wont be understood by all.

They will tend to misunderstand the 240v thing that really is not used as 240v.


Gradiens super tenui glacie.

[TG Twinkie]

It's a matter of somatic's I guess.
Since we are talking about the 120 volt legs and not the 240 volt.
When you connect a 120 volt device to one hot leg the current flows between that hot leg and the neutral. Not the other hot leg. When you use a 30 amp adaptor you are using one hot leg and the neutral. If there is 20 amps required that 20 amps is read on both the hot leg and the neutral with an ammeter.
When you use both hot legs for individual 120 volt service they both use the same neutral as the return path. If both hot legs draw 20 amps each the neutral current will be higher than a single leg but not double because of the phase shift. Thus my use of the word accumulative.

[J. Morgan]

Imagine that one leg is +120
The other leg is -120
The neutral is -0-

The trailer will make a single circuit out of the +120 and the 0

And another circuit out of the -120 and the zero.

And that is all.

There is a potential at the plug to make 240v by making a circuit out of the +120 and the -120 (=240), but the trailer does not use this.

This is pretty much how it all works, except the +120 and the -120 switch places sixty times a second.

(Technically the neutral is not Zero, but it will work as a zero for the illustration)

Gradiens super tenui glacie.

[rmkrum]

Exactly.


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[Wingeezer]

I would get a price for both in order to decide. I don't think 50 amp RV outlet would cost a great amount more and would give more flexibility in case one day you move to a motorhome or a large fifth wheel trailer, or have friends with a motorhome / fifth wheel visiting you.

If you are pretty sure neither of these things will never happen, then just stick with 30!

As for your trailer, it should be have a 30amp breaker built in it and you shouldn't be doing anything to modify it to try to draw more I don't think.

You can however plug into your 50 amp circuit (if that is what you go for) with a 50-30 adapter and you will still have the protection of the trailer's 30 amp breaker.

Brian.

[lewster]

Originally Posted by rmkrum

Uh, not quite.

The neutral carries the difference in current between the hot legs of a 220 circuit. If there is exactly zero current in one hot leg it's the worst case, and the full current is in the neutral. That's why NEC says it only needs to be the same size as the hot legs.

The phasing between the two hot leads is 180 degrees out. That's why this works.

This is why I was the go-to engineer on power distribution issues in our labs. Done this before, more than once. 50 amp connection is actually 220 volt with a neutral and safety ground (safety earth). That's why it's 4 wires. That's also why you need to be darn sure the neutral is properly connected. If it's not, serious issues ensue.

Lew? Amiright?


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RIGHT-O!!!!!

But grid voltage is presently rated for 120/240 VAC in the US, but is rapidly approaching 125/250.

If you measure any grid-supplied outlet with a quality RMS digital volt meter, you will see over 120 VAC every time.

I now see 122-123VAC on a regular basis.

Higher voltage allows for more amps to be pumped thru the same wires with no issues.

Tricky, those power folks are!!



Lew Farber