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Author Topic: 50A single phase power connection  (Read 1487 times)

JStan

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50A single phase power connection
« on: February 03, 2018, 08:04:34 PM »
I am attempting to hook up a RV power connection plug from a three phase source. there is no neutral
wire running to the box. I have 208 between phases and 120 from each phase to ground.
The I am using # 6 wire for the L1 and L2, but the ground wire is only a # 12.
Is this ground wire big enough, and do I jumper the ground to the neutral on the plug?
Do I have the correct receptacle?

SeilerBird

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Re: 50A single phase power connection
« Reply #1 on: February 03, 2018, 08:17:36 PM »
There is no neutral so there is no way to get 110 volts. You cannot used the ground as the neutral, this is illegal and very dangerous.
I would like to apologize to anyone I have not yet offended. Please be patient and I will get to you shortly.
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NY_Dutch

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Re: 50A single phase power connection
« Reply #2 on: February 03, 2018, 08:18:18 PM »
You need to run a neutral from the source to be code compliant. For 50 amp RV service, you should have two hot lines, a neutral, and a safety ground wired to a NEMA 14-50R outlet.
Dutch
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SeilerBird

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Re: 50A single phase power connection
« Reply #3 on: February 03, 2018, 08:27:07 PM »
Dutch is correct however there are two different types of three phase sources of power, delta and wye. The wye has a neutral but the delta does not have a neutral.
I would like to apologize to anyone I have not yet offended. Please be patient and I will get to you shortly.
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Gary RV_Wizard

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Re: 50A single phase power connection
« Reply #4 on: February 04, 2018, 10:06:57 AM »
Agree with Seilerbird. If you have a delta-configuration 3-phase (no neutral), you cannot supply a 50A RV outlet unless you run a neutral wire from the power source to the RV outlet.  You cannot use the ground, even if the wire is large enough (and #12 is NOT large enough anyway).

The RV expects 240v between L1 & L2 and 120v between L1-Neutral and L2-Neutral, plus a Ground as well.  Depending on the amp load in the two hot legs, the neutral may have to carry as much as 50A, so #12 wouldn't cut it anyway.
« Last Edit: February 04, 2018, 10:08:37 AM by Gary RV_Wizard »
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Isaac-1

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Re: 50A single phase power connection
« Reply #5 on: February 04, 2018, 03:04:31 PM »
Tell us more about what you are trying to do and why, also what sort of RV is it.  There may be creative work around here.  I am thinking maybe a 208V to 120V lighting transformer feeding 50 amp 120V into a 120/240V 50 amp RV outlet, this would only supply 120V RV items at half the total watts of a normal 50 amp 120/240V RV hookup, but still more than a 120V 30 amp rv hookup, and should work if you have no 240V appliances onboard.

perhaps something similar to this https://www.ebay.com/itm/SQAURE-D-15T85HIS-U-15KVA-208Pri-208-120Sec-USED/282145940399
« Last Edit: February 04, 2018, 03:10:14 PM by Isaac-1 »
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xrated

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Re: 50A single phase power connection
« Reply #6 on: February 04, 2018, 04:36:05 PM »
If you have 208 volts between the phases....A to B, A to C, and B to C, they you have a WYE connected output from the transformer that is feeding the box.  If this is the configuration, there SHOULD be a neutral wire associated with that output from the transformer feeding the box.  The actual neutral wire may not be in the box, but that may be because the box was originally used to feed a 3 phase WYE connected motor.  But, if the secondary (the leads that should be marked a, b, and c) of that transformer are in fact 208 volts from phase to phase, it is a WYE connection.  And if you are unfamiliar with electrical transformers or electrical in general, hire a qualified Electrician that knows the transformer configurations and how to hook things up. 
« Last Edit: February 04, 2018, 04:44:04 PM by xrated »
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Rene T

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Re: 50A single phase power connection
« Reply #7 on: February 09, 2018, 02:28:45 PM »
Why is it so hard for members to reply. It would be so helpful to know if the OP was helped.
To all members, please get back into your post and let us know if we were able to help you.
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RedandSilver

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Re: 50A single phase power connection
« Reply #8 on: February 09, 2018, 03:05:15 PM »
Why is it so hard for members to reply. It would be so helpful to know if the OP was helped.
To all members, please get back into your post and let us know if we were able to help you.
:)) :)) :))


Those one post wonders seem to never come back especially if they don't get the answer they were looking for.
They fail to understand that we are looking out for their best interests and trying to keep them safe.

Failing to update us not only keeps us wondering what happened but is also doesn't help anyone else that has the same problem
or question and was hoping for an solution to their problem.

Is it time to attach a note when someone registers like:  IF you post a question and replies are received you are kindly asked
to reply whether or not it helped you.  Because this is an active forum a reply within 24-48 is requested if at all possible.
Your consideration is much appreciated - we hope you understand the benefit to others it can provide.
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TonyDtorch

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Re: 50A single phase power connection
« Reply #9 on: February 09, 2018, 04:10:53 PM »
Ground (earth) and Neutral are the same electrical points.

Neutral and earth are connected together at the point of power generation... and at the output of each transformer in a transmission system.
Neutral and earth are also connected together at the breaker panel in a typical home installation.

https://electronics.stackexchange.com/questions/185028/what-is-the-difference-between-neutral-and-ground

« Last Edit: February 09, 2018, 04:26:56 PM by TonyDtorch »

mikeylikesit

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Re: 50A single phase power connection
« Reply #10 on: March 06, 2018, 12:40:36 PM »
Ground (earth) and Neutral are the same electrical points.

Neutral and earth are connected together at the point of power generation... and at the output of each transformer in a transmission system.
Neutral and earth are also connected together at the breaker panel in a typical home installation.

https://electronics.stackexchange.com/questions/185028/what-is-the-difference-between-neutral-and-ground

While your point is well taken, and technically correct, it would not apply to the OP's situation.  BONDING of the neutral and ground conductors is allowed only in the MAIN electrical panel in a residential service.

there are VERY GOOD REASONS that the NEC does not allow the ground conductor be used as a neutral.   
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_Rusty_

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Re: 50A single phase power connection
« Reply #11 on: March 06, 2018, 01:24:30 PM »
If you have 208 volts between the phases....A to B, A to C, and B to C, they you have a WYE connected output from the transformer that is feeding the box.  If this is the configuration, there SHOULD be a neutral wire associated with that output from the transformer feeding the box.  The actual neutral wire may not be in the box, but that may be because the box was originally used to feed a 3 phase WYE connected motor.  But, if the secondary (the leads that should be marked a, b, and c) of that transformer are in fact 208 volts from phase to phase, it is a WYE connection.  And if you are unfamiliar with electrical transformers or electrical in general, hire a qualified Electrician that knows the transformer configurations and how to hook things up.

Could you clarify the underlined remark?  It sounds like you repeated something incorrectly (from the first sentence).   It all sounds correct though, except...that line highlighted.
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xrated

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Re: 50A single phase power connection
« Reply #12 on: March 06, 2018, 02:04:39 PM »
The primary side of the transformer that is fed from whatever power company/utility, would likely be marked as phase A, phase B, and phase C (Capital letters).  The secondary side of the transformer, the side that the OP says that there is 208VAC phase to phase, would likely be marked...phase a, phase b, and phase c......all small letters.  I've seen different markings on transformers also.  The letter "H", as in H1, H2, and H3 for the primary side of the transformer.  Then the letter "X" for the secondary side...X1, X2, and X3.  On a WYE connected system the neutral is of course going to be marked "N".

Normally, the phase markings are going to be the A,B,C nomenclature, and where they land the wire, (in this case...a three phase transformer), will be labelled "H" for the primary side and "X" for the secondary side.

Hope that clears it up for you.
« Last Edit: March 06, 2018, 02:09:59 PM by xrated »
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Bob T

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Re: 50A single phase power connection
« Reply #13 on: March 06, 2018, 03:51:36 PM »
Itís been my experience that the feed to the transformer would be phased ďA,B &CĒ
Assume for a minute the primary into transformer is 600V (could be 575 whatever), the transformer is wound 600/120/208V, delta primary!wye secondary.
The primary conductors would land on H1, H2 and H3. No neutral on primary side.  The secondary conductors would also be refered to as phases A,B and C but they would land on X1, X2 and X3.
A neutral should be carried from the X0 point to lower voltage panel/load. It is in the transformer where the grounding is done. Ground is connected to X0 and case in transformer and other end of ground conductor is terminated at building ground or there are other acceptable places this can be connected.
Thats the way itís done up here in the north.
Hope this helps a bit to clarify.
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SargeW

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Re: 50A single phase power connection
« Reply #14 on: March 06, 2018, 04:57:47 PM »
Even if the OP didn't come back, I still  find the thought process interesting.  And I am always impressed by the depth of knowledge of our members. 

It's true, some new posters are only interested if they get a favorable response that confirms what they want to do. If not they are off to some other forum to answer shop.  Either way, I still think it's a learning experience for us readers. Feel to continue to post.......
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SeilerBird

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Re: 50A single phase power connection
« Reply #15 on: March 06, 2018, 04:59:47 PM »
Just because he did not post a second time does not mean he did not read the responses.
I would like to apologize to anyone I have not yet offended. Please be patient and I will get to you shortly.
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kdbgoat

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Re: 50A single phase power connection
« Reply #16 on: March 06, 2018, 05:43:57 PM »
Just because he did not post a second time does not mean he did not read the responses.

Check his profile. He hasn't been back, at least not logged in under his username.
I know you believe you understand what you think I said,
But I am not sure you realize what you heard is not what I meant


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SeilerBird

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Re: 50A single phase power connection
« Reply #17 on: March 06, 2018, 05:52:53 PM »
Check his profile. He hasn't been back, at least not logged in under his username.
You don't have to log in to view this site.
I would like to apologize to anyone I have not yet offended. Please be patient and I will get to you shortly.
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kdbgoat

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Re: 50A single phase power connection
« Reply #18 on: March 06, 2018, 05:58:04 PM »
True, that's why I said he hadn't been back using his username.
I know you believe you understand what you think I said,
But I am not sure you realize what you heard is not what I meant


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xrated

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Re: 50A single phase power connection
« Reply #19 on: March 06, 2018, 06:34:24 PM »
It’s been my experience that the feed to the transformer would be phased “A,B &C”
Assume for a minute the primary into transformer is 600V (could be 575 whatever), the transformer is wound 600/120/208V, delta primary!wye secondary.
The primary conductors would land on H1, H2 and H3. No neutral on primary side.  The secondary conductors would also be refered to as phases A,B and C but they would land on X1, X2 and X3.
A neutral should be carried from the X0 point to lower voltage panel/load. It is in the transformer where the grounding is done. Ground is connected to X0 and case in transformer and other end of ground conductor is terminated at building ground or there are other acceptable places this can be connected.
Thats the way it’s done up here in the north.
Hope this helps a bit to clarify.

In your scenario, you are assuming a Delta/Wye configuration.  There are Delta/Delta, Delta/WYE, WYE/WYE, WYE/Delta, and other less used configurations......which are almost endless (not really, but there are a bunch).  The point that I was trying to make is that the O.P. stated that he had 208VAC from phase to phase.....which is indicative of a WYE configuration, not DELTA.  The other point that I was trying to make is that he appears to have NOT found the neutral wire in his box, which would allow him to get 120VAC from any one of the phases...A, B, or C..and the neutral.  I also pointed out, since I don't know what the 208VAC 3 phase power was originally used for, that it might have been to supply 3 phase power (208VAC to a smallish 3 phase motor that was hooked up for low voltage, as opposed to a more common 3 phase 480VAC.  Almost all modern day 3 phase motors, especially of the smaller H.P. variety are capable of being connected for "Low or High" voltage.....with low being 208 and high being 480.

And, on a side note, the primary side of the transformer is almost certainly not 600V or 575.  The utilities that bring power into commercial businesses are generally 6900-7200VAC.  In our plant (which is very old), the utilities bring in 161,000 VAC and several large transformers around the plant step that down to a very common 13.8Kv.  13.8Kv is the distribution lines that are all over the plant and feed various transformers via LBS's, fuse cutouts, etc.  That 13.8Kv is than stepped down again, depending on the need, to 2300VAC, 4160VAC and a few....very few, 600VAC transformers.  The 2300 and 4160 transformers then step down again to other needed voltages......480VAC is the most common, but there are plenty of  208/120VAC WYE connected transformers too.

So, there you have it......electricity in a nutshell! 
« Last Edit: March 06, 2018, 06:52:14 PM by xrated »
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Bob T

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Re: 50A single phase power connection
« Reply #20 on: March 06, 2018, 07:50:05 PM »
I understand what youíre saying.
I used 600V to keep it simple. I was in no way refering to large power. (personally, I have experience up to 500KV but no one wants to hear about that)
I also mentioned panel/load. Youíre right, the neutral doesnít need to be carried out if its only 3 phase load. In that case the N in transformer would be booted (but the XO would still be grounded to facilitate clearing faults).
As I said, just trying to simplify things a bit for average folks that have no interest or desire to learn our trade.
I donít know about you but I deal with this stuff every day for tooo many years and generally donít care to even talk about it on my off time.
Take care and have a great evening.
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xrated

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Re: 50A single phase power connection
« Reply #21 on: March 06, 2018, 08:01:50 PM »
I understand what youíre saying.
I used 600V to keep it simple. I was in no way refering to large power. (personally, I have experience up to 500KV but no one wants to hear about that)
I also mentioned panel/load. Youíre right, the neutral doesnít need to be carried out if its only 3 phase load. In that case the N in transformer would be booted (but the XO would still be grounded to facilitate clearing faults).
As I said, just trying to simplify things a bit for average folks that have no interest or desire to learn our trade.
I donít know about you but I deal with this stuff every day for tooo many years and generally donít care to even talk about it on my off time.
Take care and have a great evening.

I'm getting to that point...somewhat.  I've been in the Electrical trade since 1977 and topped out in 1980.  I've got about 18 more months and I'm hanging it up for a much more relaxed time.....camping, riding my motorcycle, biking, hiking, and ????  Have a good evening yourself and thank you for your input.   :D
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SeilerBird

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Re: 50A single phase power connection
« Reply #22 on: March 06, 2018, 08:11:14 PM »
I retired in 1989 after over 20 years in the trade and I hate to even change lightbulbs. :o
I would like to apologize to anyone I have not yet offended. Please be patient and I will get to you shortly.
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Isaac-1

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Re: 50A single phase power connection
« Reply #23 on: March 06, 2018, 08:18:05 PM »
Keep in mind there is a lot of guessing going on here, we have no idea what sort of location the OP was dealing with, so sure 600VAC, 480VAC, etc is common in most industrial facilities, keep in mind it might have been far simpler than this, such as a light industrial warehouse being fed relatively common 120/208 3 phase wye from a pole top transformer and he was trying to tap into at a conveniently located sub panel or disconnect switch that was installed at some point in time to power a now removed 208V wash down pump, electric forklift charger, or some such, both of which would generally not have a neutral connection.

In my limited experience such legacy, mystery panels and switches are common in older light industrial warehouses.  One comes to mind where there is a 60 amp disconnect on an exterior wall of a warehouse building, and no one has a clue why it is there, or even a guess why it would have ever been put there as it was not near any potential load, the best guess was it dated back to the construction of the warehouse, and may have been used to provide power to a contractor office trailer.
« Last Edit: March 06, 2018, 08:22:13 PM by Isaac-1 »
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mikeylikesit

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Re: 50A single phase power connection
« Reply #24 on: March 06, 2018, 09:17:22 PM »
I'm just hoping that the reason the OP isn't chiming in is NOT because he was unsuccessful in his attempt at wiring his rig.
 :o
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TonyDtorch

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Re: 50A single phase power connection
« Reply #25 on: March 06, 2018, 11:36:28 PM »
there are VERY GOOD REASONS that the NEC does not allow the ground conductor be used as a neutral.


After years of dealing with electrical inspectors all over America and other countries,  I have determined the NEC is just like the Bible...

Depending on who is reading it....it can be made to say everything is wrong.     ;)

« Last Edit: March 06, 2018, 11:59:51 PM by TonyDtorch »

Bob T

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Re: 50A single phase power connection
« Reply #26 on: March 07, 2018, 04:35:08 AM »
Congrats on the 18 months xrated   :)).  The end is in sight.
Myself, I am done in September.

Iím like a kid in a candy store now. Excited again!

Oh well, off to work now. Have a great day everyone.
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xrated

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Re: 50A single phase power connection
« Reply #27 on: March 07, 2018, 05:15:25 AM »
Congrats on the 18 months xrated   :)).  The end is in sight.
Myself, I am done in September.

Iím like a kid in a candy store now. Excited again!

Oh well, off to work now. Have a great day everyone.

Congratulations......Sept. is just around the corner, that's awesome.  Enjoy your retirement and live everyday to the fullest.

There is one problem with retirement though, as I understand it......You never have a SCHEDULED day off!   8)
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NY_Dutch

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Re: 50A single phase power connection
« Reply #28 on: March 07, 2018, 07:31:21 AM »
"W
Congratulations......Sept. is just around the corner, that's awesome.  Enjoy your retirement and live everyday to the fullest.

There is one problem with retirement though, as I understand it......You never have a SCHEDULED day off! 

Her: "What are you going to do today?" Him: "Nothing..." Her: "That's what you did yesterday." Him: " I'm not done yet."  ;D
Dutch
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xrated

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Re: 50A single phase power connection
« Reply #29 on: March 07, 2018, 07:40:29 AM »
"W
Her: "What are you going to do today?" Him: "Nothing..." Her: "That's what you did yesterday." Him: " I'm not done yet."  ;D

I've actual used that line except that I added a little to it......"I'm not done yet, and you know that I'm NOT a quitter"   ;D
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