50amp on 120/208 service

[Bill_Satellite]

I know most systems are setup on 120/240 systems but I need to have a plug installed in a commercial building that has 3 phase lines coming in and power options are 120 and 208. I don't see where that would be an issue as I would have 2 good 120V legs but between the 2 legs it would read 208. I don't use 240 (or 208) anywhere in the coach and don't see why this would be an issue but I would love someone to confirm that I am right or give me a warning that something with this setup could be an issue.
Thanks all.

[Bill_Satellite]

All is good! Hooked up and happy!

[wa8yxm]

vermilye wrote:
Then there is the 120V Delta. We had one in one of our older theaters. "Shocks" new electricians the first time they meter one. 120V between everything...

Was that a "Theater in the round" (full circle) 120+120+120 = 360
(And yes I am joking).

[vermilye]

Then there is the 120V Delta. We had one in one of our older theaters. "Shocks" new electricians the first time they meter one. 120V between everything...

[joshuajim]

Don’t forget Delta and Wye :B :B. :B

[Bill_Satellite]

23hotrodr wrote:

Bill.Satellite wrote:
We discussed the install and the installer was very familiar with an RV plug. I had just never seen the 208 setup and was looking for confirmation that using that was not a problem since I never use anything other than 120.

Since you have confirmed the electrician will properly wire the receptacle--

208 3 phase will yield the following in your situation--

208 volts across 2 hot leads
115 volts from each hot to neutral

This will work perfectly fine. You can and should confirm it with a volt meter. Good luck-- Mick

Thanks. I already had planned to do that!

[23hotrodr]

Bill.Satellite wrote:
We discussed the install and the installer was very familiar with an RV plug. I had just never seen the 208 setup and was looking for confirmation that using that was not a problem since I never use anything other than 120.

Since you have confirmed the electrician will properly wire the receptacle--

208 3 phase will yield the following in your situation--

208 volts across 2 hot leads
115 volts from each hot to neutral

This will work perfectly fine. You can and should confirm it with a volt meter. Good luck-- Mick

[Bill_Satellite]

We discussed the install and the installer was very familiar with an RV plug. I had just never seen the 208 setup and was looking for confirmation that using that was not a problem since I never use anything other than 120.

[CA_Traveler]

The 3 wire 240V dryer plug looks similar to the 3 wire 120V 30A RV plug. And other than for a RV the 30A RV plug is rarely used. So some electricians and non electricians wire the RV plug with 240V which lets the smoke out.

[wa8yxm]

Bill.Satellite wrote:
Not sure why anyone thought I was going to try to install this myself, but I have 2 professionals installing the plug but not all professionals understand exactly what is required of RV's. They know what an RV plug is and the wiring required. I just wanted a little reassurance that they understood what I hoped they understood and it appears that they do. Hopefully, they will get the work done this week or next and I will be plugged in 30 seconds from the office!

First: Why do we warn about having a PRO do the job? You are not the only one who will read our words and then take action.. So we have to cover the "other folks" who may not be a smart as you.. I mean "DO NOT EAT THE TIDE PODS" or the sign in the supermarket "Product may contain peanuts" (It's on the peanut shelf).. People that stupid may be reading this thread.

Second. NOT ALL PROFESSIONAL ELCTRICANS (in fact darn few) UNDERSTAND RV WIRING

Oh they are good on 50 amps.. Hook it up just like an electric range.

But on 30.. many have fried their expensive electronics when the PROFESSIONAL hooked it up wrong..

Personal story (no damage) I installed my own 30 amp.. Properly

But I was looking for an electrical switch.. Special switch. and while I was in the supply store an electrician was buying a TT-30.. I warned him it was a 125 volt outlet and pointed out where it said so right on the outlet itself.. HE Thanked me as he was about to hook it up WRONG and fry his client's electronics. Now that is ONE electrician who knows.. How many ELectricians are there in the Flint MI area and that ONE knows.

Back when I wore a younger man's cloths I went to school and as a result am a Certified Electroincs Technician. Did not work long in that field. but the Cert is lifetime.

I also have a 50 year membership pin in the American Radio Relay League INC. licensed 51 years ago.

[ScottG]

CA Traveler wrote:

DrewE wrote:
Although the two phases are 120 degrees from each other, the phase to phase waveform still works out to be a sine wave, so it's "normal" single phase power albeit at a lower voltage. There are plenty of single-phase motors that are rated to operate at either 208V or 240V (and likewise plenty that are not so rated).

Sine waves for sure. But a 240V motor sees that the combined voltage and amps are 120 degrees out of phase with each other. So definitely no longer 240V single phase.

As long as the motor and it's load is designed for both power sources then all is good. Appreciate the input.

The 240V is still single phase:
Split phase

[DrewE]

CA Traveler wrote:

DrewE wrote:
Although the two phases are 120 degrees from each other, the phase to phase waveform still works out to be a sine wave, so it's "normal" single phase power albeit at a lower voltage. There are plenty of single-phase motors that are rated to operate at either 208V or 240V (and likewise plenty that are not so rated).

Sine waves for sure. But a 240V motor sees that the combined voltage and amps are 120 degrees out of phase with each other. So definitely no longer 240V single phase.

As long as the motor and it's load is designed for both power sources then all is good. Appreciate the input.

From the motor's point of view, the voltage isn't out of phase at all since it has no neutral connection. It's just a (single-phase) 208V 60Hz AC power supply; the motor behaves precisely as if it were connected to a variac or similar device set to 208V. The current may not--indeed generally will not--be perfectly in phase because the motor is inductive and has a non-unity power factor; but it's not offset from the voltage in any atypical way. (The current waveform in a constant voltage system, such as the modern electrical grid, is of course determined by the characteristics of the load, and not directly dictated by the supply.)

[CA_Traveler]

ScottG wrote:

Cummins12V98 wrote:

HMMMMM, I have a 220V Washer AND Dryer. I also have 220V Cheap Heat.

I'm curious, what happens if you turn on your washer, drier or CH when plugged into 30A (120)?
Or do they just expect us to be smarter than that.. 😄

Interesting question.

Some aspects of the appliance might work. Imagine that the control panel and the motor work on 120V and a day later the clothes aren't dry. :h

[Cummins12V98]

ScottG wrote:

Cummins12V98 wrote:

HMMMMM, I have a 220V Washer AND Dryer. I also have 220V Cheap Heat.

I'm curious, what happens if you turn on your washer, drier or CH when plugged into 30A (120)?
Or do they just expect us to be smarter than that.. 😄

No idea. If I were plugged into just 120 I would not use them. If I need them I would fire off my 220v 6500 Cummins Commercial gen.

[CA_Traveler]

DrewE wrote:
Although the two phases are 120 degrees from each other, the phase to phase waveform still works out to be a sine wave, so it's "normal" single phase power albeit at a lower voltage. There are plenty of single-phase motors that are rated to operate at either 208V or 240V (and likewise plenty that are not so rated).

Sine waves for sure. But a 240V motor sees that the combined voltage and amps are 120 degrees out of phase with each other. So definitely no longer 240V single phase.

As long as the motor and it's load is designed for both power sources then all is good. Appreciate the input.