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50 amp service from 3 phase power

Yahoo Message Number: 91558
I want to install a 50 amp service for my coach at my shop where we have 3 phase power. Is there any issue with using 2 of the 3 hot legs for a 50 amp RV service plug?

Thanks in advance.

Greg Jones

'03 Intrigue 11571

Re: 50 amp service from 3 phase power

Reply #1 –
Yahoo Message Number: 91559
Depends on which type of 3 phase you have. Which 3 phase do you have? 3 wire or 4? 208, 240, 480?

Mikee

Re: 50 amp service from 3 phase power

Reply #2 –
Yahoo Message Number: 91560
Also, do you need just 120 or do you need 240 as well?

Mikee

Re: 50 amp service from 3 phase power

Reply #3 –
Yahoo Message Number: 91561
Greg as long as you have 120/208 3 phase and you use two legs and the neutral & a ground with a 50 amp 2 pole breaker & #6 wire you will be OK.

Jim 2006 Inspire # 51668

Re: 50 amp service from 3 phase power

Reply #5 –
Yahoo Message Number: 91563
As long as he only needs 120 on 2 legs and does not need 240, this will work. If he has 240 volt stuff in the coach then it is a little different.

Mikee

Re: 50 amp service from 3 phase power

Reply #6 –
Yahoo Message Number: 91564
It's 4 wire. Not 480 but, I'm not sure if it's 208 or 240. I think it's 240 but, I don't have my meter today.

Greg

Re: 50 amp service from 3 phase power

Reply #7 –
Yahoo Message Number: 91565
ThaT's whaT I did. Mine coMes in 480 volts and I run it through a transformer to get the desired Voltage.

Sent from my mobile Phone

greg@... wrote:

Re: 50 amp service from 3 phase power

Reply #8 –
Yahoo Message Number: 91566
If it is 208 and you do not need 240 in the coach then you are okay. If it is 120/240 then you are good to go either way.

Mikee

Mikee

Re: 50 amp service from 3 phase power

Reply #9 –
Yahoo Message Number: 91567
I only need 120. I could actually easily make do with a 120V30 amp service but, I already have a pitail with the correct 50 amp plug for the coach.

I appreciate the help!
Greg

Re: 50 amp service from 3 phase power

Reply #10 –
Yahoo Message Number: 91569
If the service is 240 3 phase then it is a delta connection and there is no relationship between the neutral and the phase voltages. You can not use it for this application as there is no 120 volts to the neutral. It can not be a 120/240 volt 3 phase 4 wire connection as that is physically impossible. The phase to neutral always has a vector repationship as in 120/208 volt. You can use the 120/208 volts for a 3 wire connection but any 240 volt appliances will not see 240 volts. Also with 50 amps flowing in each phase the neutral current will also be 50 amps and not zero as in a 120//240 volt single phase connection.

Re: 50 amp service from 3 phase power

Reply #11 –
Yahoo Message Number: 91570
120/240 delta 3 phase does have a neutral. It is in the middle of one of the legs.

Look it up.

Mikee

Re: 50 amp service from 3 phase power

Reply #12 –
Yahoo Message Number: 91571
Here is a link to a picture

http://www.google.com/imgres?imgurl=http://electrical-contractor.net/BCodes/ED's4Wdelta2_(2).JPG&imgrefurl=http://www.electriciantalk.com/f9/120-240-volt-3-phase-delta-high-leg-5166/&h=400&w=590&sz=35&tbnid=tDmX_K_26j1nDM:&tbnh=71&tbnw=105&zoom=1&usg=__1fSBDiYsZhTfNEZchR8WyfwcJa4=&docid=RHXSWAjHK1i0sM&sa=X&ei=Ca9EUuONNYbW9QTozYGoDg&ved=0CE0Q9QEwBA
Mikee

Re: 50 amp service from 3 phase power

Reply #13 –
Yahoo Message Number: 91572
One of the legs to neutral on a 240 delta circuit is called a "wild leg". It will have a voltage to neutral of around 197 volts. The other two legs will be around 120 to neutral and 240 between them.

Norm

Re: 50 amp service from 3 phase power

Reply #14 –
Yahoo Message Number: 91573
But not the legs that have the neutral. All 3 phase has a wild leg.

Mikee

Re: 50 amp service from 3 phase power

Reply #15 –
Yahoo Message Number: 91574
As I remember I never had the wild leg problem on Y connected 208 volt 3 phase, only on delta connected 240 volt 3 phase. .

Norm 2004 Intrigue #11773

Re: 50 amp service from 3 phase power

Reply #16 –
Yahoo Message Number: 91578
What in the coach needs 240 volts? the 120/208 will give him two 120 volt lines and that's all he needs

Jim 2006 Inspire #51668

Re: 50 amp service from 3 phase power

Reply #18 –
Yahoo Message Number: 91581
If it is 120/240 Delta make sure you don't use the stinger leg as that will have higher voltage to the neutral,

Jim 2006 Inspire #51668

Re: 50 amp service from 3 phase power

Reply #19 –
Yahoo Message Number: 91582
Mikee Not if is a Y system, with a Y system all 3 legs to neutral will have the same voltage.

Jim 2006 Inspire #51668

Re: 50 amp service from 3 phase power

Reply #20 –
Yahoo Message Number: 91583
Aquahot does upply a 240 volt electric heat element in one of it's larger models. i never owned an all electric coach so I don't know if any of those have any 240 volt applications.

A 240 volt 3 phase servicce is intended to supply 3 phase load only. Most are 3 wire and do not extend any neutral connection. Yes there are hybreds particularily where the delta is formed using 3 single 120/240 volt single phase transformers. Each transformer has a center tapped secondary coil and one of them can be connected to the neutral. However a delta is a closed loop connection and it does not handle imbalanced loads very well. Current can circulated around the loop and depending on the installed capacity vs the single phase load, some nasty voltage problem can develope. Make sure you know exctly what you are working with and can handle some 3 phase vector math.

Re: 50 amp service from 3 phase power

Reply #21 –
Yahoo Message Number: 92138
As usual, the knowledge in this group and willingness to help out is amazing.

Thanks to all who posted. I finally got around to checking the voltage in the compressor house where I intend to install my outlet. It is a four wire connection. From ground (obvious because it was tied to the metal box) the other 3 legs read 110, 110 and 190? My logic says to use the two 110 legs and ground but, my logic has gotten me in a lot of trouble in the past. A 30 amp connection would suit my purposes as well. All I really want is enough juice to run a small space heater so I don't have any freezing problems in the relatively mild Eugene Oregon winters.
Don, I so can't handle 3 phase vector math that I don't even know what it is! Am I looking for trouble here?
Thanks again,
Greg
'03 Intrigue 11571

Re: 50 amp service from 3 phase power

Reply #22 –
Yahoo Message Number: 92140
You have 3 phase with a high leg. Just use the two legs that are 120 to ground 240 between the phases. Make sure and fuse it with a fuse-able disconnect or breaker enclosure with a 30 amp breaker. You can use the 10' tap rule per the National Electrical Code. You need a neutral (2 hots neutral and a ground) that your pump service may not have.

Note the wire that is feeding the pump house is sized for the loads in the pump house, your additional 30 amp load may not be very well tolerated.

We electricians are very reasonable and less than a new transfer switch or inverter!!

Nathan

1998 Allure

Re: 50 amp service from 3 phase power

Reply #23 –
Yahoo Message Number: 92141
? As Nathan pointed out 2 hots a neutral and ground for 50 amp service, nice explanation Nathan. Do it wrong and you will let the smoke out of all your expensive electronics! :( In case you didn't know electronics run on smoke, no mirrors, and if you let it out they no work anymore.
So as Nathan also pointed out if you are not comfortable with the electric hire an knowledgeable electrician even they die messing with 3 phase.

Ray O'Connell

They say wine improves with age! As I enter my golden years, I say age improves with wine! The Born Loser

Re: 50 amp service from 3 phase power

Reply #24 –
Yahoo Message Number: 92145
?
Greg,

Not knowing all of the details here, I am forced to answer your question with a yes you may be asking for trouble. If you extend 2 of the 3 phase legs then the voltage between each will be 240 volts but also they will be out of phase with each other by 120 degrees. That is not the case in a single phase 240/120 volt service where there in no phase angle involved.
This is no time to be casual about actual voltages. You said 110 from each phase to the metal case that appears to be grounded. You did not however say what the phase to phase voltage was at the same time. I'm not being picky as there could be a difference in this case especially since I am not hearing what the voltage is to the neutral. You said it was a 3 phase 4 wire feed to the pump. Why did you not measure the phase to neutral voltage?
The normal 30 amp service in RV parks is a 120 volt service not a 240/120 volt service. I don't see why you would need both phases if all you need is 120 volts. In any case you can not use the ground in place of the neutral. If you extend this as a 30 amp service to the coach it has to be the phase, the neutral and the ground. In my opinion it would be a lot simpler than using the 2 phases. BTW what is the voltage specified on the pump label.
I also agree with someone's comment about the additional load on the wiring that may not be adequate. Most space heaters are 1500 watt and draw from 12 to 15 amps depending on the actual voltage. The thought about using a licensed electrician is certainly not a bad idea I am a Power Engineer not an electrician. Everything that an electrician does must conform to the electrical code.

Don Seager

As usual, the knowledge in this group and willingness to help out is amazing.

Thanks to all who posted. I finally got around to checking the voltage in the compressor house where I intend to install my outlet. It is a four wire connection. From ground (obvious because it was tied to the metal box) the other 3 legs read 110, 110 and 190? My logic says to use the two 110 legs and ground but, my logic has gotten me in a lot of trouble in the past. A 30 amp connection would suit my purposes as well. All I really want is enough juice to run a small space heater so I don't have any freezing problems in the relatively mild Eugene Oregon winters.

Don, I so can't handle 3 phase vector math that I don't even know what it is! Am I looking for trouble here?

Thanks again,
Greg

'03 Intrigue 11571

---In country-coach-owners@yahoogroups.com, wrote:

Aquahot does upply a 240 volt electric heat element in one of it's larger models. i never owned an all electric coach so I don't know if any of those have any 240 volt applications.

A 240 volt 3 phase servicce is intended to supply 3 phase load only. Most are 3 wire and do not extend any neutral connection. Yes there are hybreds particularily where the delta is formed using 3 single 120/240 volt single phase transformers. Each transformer has a center tapped secondary coil and one of them can be connected to the neutral. However a delta is a closed loop connection and it does not handle imbalanced loads very well. Current can circulated around the loop and depending on the installed capacity vs the single phase load, some nasty voltage problem can develope. Make sure you know exctly what you are working with and can handle some 3 phase vector math.