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Old 01-18-2008, 03:51 PM   #1
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240 Volts - 4 wire to 3 wire


I play in a band and sometimes the place we're playing doesn't have enough dedicated circuits nearby for our equipment but often times they will have a 240V receptacle available.

I have a 6 circuit "sub-panel" that I built and use for this purpose with a 3-wire NEMA 10-50 matching range cord. In this box I have the neutral bar tied to the box/ground.



This works fine for most applications except for when the 240V receptacle available is a NEMA 14-50 configuration and does not match the plug for my panel. For these situations I need to make an adapter cord.

To adapt from a 14-50 (4 wire) to a 10-50 (3 wire) do I want to drop the neutral or the ground?

Just want to make sure I am doing this the correct way.

Thanks

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Old 01-18-2008, 05:12 PM   #2
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240 Volts - 4 wire to 3 wire


You may have some liability issues defeating the equipment ground with an adapter to go from 3 wire to 4 wire. This is done in the RV world but it is usually 4 wire 50 amp to 3 wire 30 amp.

On your present set up those receptacles must have gfci protection.

Maybe just make up a like system for 4 wire only?

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Old 01-18-2008, 09:03 PM   #3
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240 Volts - 4 wire to 3 wire


Quote:
do I want to drop the neutral or the ground?

You don't want to drop either, they must be tied together.

There is no really "proper" way to make your system code compliant with a 3 wire source. Nobodys is going to die but it won't be compliant. The only place where the neutrals and grounds can be together is at the service (where the power first comes to the building),


Be CAREFUL where you plug into. Bars are notorious for having shoddy electrical work. Check voltage and polarity ALWAYS. I was a drummer/sparky many years ago and have seen some stuff. A lost neutral can easily supply 240V to all your 120V outlets. Draw the circuit (with something plugged in/turned on) and you will see how.

One time in Phoenix I got the CRAP shocked out of me setting up my lighting system via reversed polarity in a 120v outlet. A bar in Albuquerque had huge ALLIGATOR CLIPS on the main panel lugs to provide stage power.
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Old 01-19-2008, 01:45 AM   #4
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240 Volts - 4 wire to 3 wire


Same reason a buddy of mine told me to check the mic with the back of my hand. Sometimes the polarity is wrong. If it wants to grab you it will. If you offer the back of your hand, well the odds are in your favor. Agree 150%. Bars/clubs have some of the most questionable electric around.
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Old 01-19-2008, 02:10 AM   #5
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240 Volts - 4 wire to 3 wire


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Maybe just make up a like system for 4 wire only?
That would be the ideal way to handle it but I have a 150 foot spool of 6/3 cable that I use for long runs when necessary, bought it many years ago when the power sources I was using were mostly all 3 wire. I'd rather not shell out for 150 feet of 6/4.

I'm not so much concerned about being compliant as I am about having good power. Never ran into any truly bad power at bars so far. Other than a hum once in a while I've had pretty good luck getting clean power.

Quote:
A lost neutral can easily supply 240V to all your 120V outlets.
I experienced this within the last year. The neutral on the socket end of my extension cable somehow worked its way loose after years of use. I lost a number of light bulbs but I use a voltage regulator/power conditioner that protected the delicate electronics. That could have been a disaster and it reminds me that I need to check the cable ends periodically.

Thanks for all of your input.
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Old 01-19-2008, 09:28 AM   #6
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240 Volts - 4 wire to 3 wire


Quote:
Originally Posted by Richo View Post

I'm not so much concerned about being compliant as I am about having good power. Never ran into any truly bad power at bars so far. Other than a hum once in a while I've had pretty good luck getting clean power.

Thanks for all of your input.
Hums or buzz's are not related to good/bad power, they are caused from ground loops...
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Old 01-19-2008, 11:29 AM   #7
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240 Volts - 4 wire to 3 wire


The hum usually happens when we're using the bar's wall receptacles instead of getting our own feed off the panel or other 240 V source.
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Old 01-19-2008, 12:16 PM   #8
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240 Volts - 4 wire to 3 wire


Other than replacing the recept's with GFCI's, I guess you don't have much choice do you? There is no garranty your going to get 4 wires or 3 at any givin bar recept.
Your panel looks real nice.
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Old 01-19-2008, 06:30 PM   #9
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240 Volts - 4 wire to 3 wire


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The hum usually happens when we're using the bar's wall receptacles instead of getting our own feed off the panel or other 240 V source.

The hums usually happened when we got too buzzed and forgot the lyrics.
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Old 01-19-2008, 08:57 PM   #10
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240 Volts - 4 wire to 3 wire


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The hums usually happened when we got too buzzed and forgot the lyrics.
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Old 01-20-2008, 11:48 PM   #11
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240 Volts - 4 wire to 3 wire


LOLOLOLOLOLOLOLOLOLOLOLOLOLOL. Thanks.
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Old 02-24-2008, 12:05 PM   #12
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240 Volts - 4 wire to 3 wire


what is a ground loop
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Old 02-24-2008, 12:48 PM   #13
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240 Volts - 4 wire to 3 wire


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what is a ground loop
http://ecmweb.com/grounding/electric...fixing_ground/
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Old 02-24-2008, 01:09 PM   #14
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240 Volts - 4 wire to 3 wire


Quote:
Originally Posted by Richo View Post
I play in a band and sometimes the place we're playing doesn't have enough dedicated circuits nearby for our equipment but often times they will have a 240V receptacle available.

I have a 6 circuit "sub-panel" that I built and use for this purpose with a 3-wire NEMA 10-50 matching range cord. In this box I have the neutral bar tied to the box/ground.



This works fine for most applications except for when the 240V receptacle available is a NEMA 14-50 configuration and does not match the plug for my panel. For these situations I need to make an adapter cord.

To adapt from a 14-50 (4 wire) to a 10-50 (3 wire) do I want to drop the neutral or the ground?

Just want to make sure I am doing this the correct way.

Thanks
Well.... there's really no correct way in your case... Only less wrong ways.

But, if you have to make an adapter, then you would want to drop the ground from the 4-wire setup. I know I will probably get flamed from others for that, but my reasoning is that if you drop the neutral, then your neutral current from your rig will return on the ground of the system, that isn't ideal.

Since you are going to make it anyway, and you are going to use the 3-wire setup, you're better off loosing the ground in the 4-wire. And as others have pointed out, GFCI receptacles would be ideal in this case, but...

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Old 02-24-2008, 02:03 PM   #15
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240 Volts - 4 wire to 3 wire


In my humble opinion only:

Assisting you do something wrong is really not what professional electricians should be doing. I see a sub panel in your picture. The grounding (ground) conductor cannot be bonded to the grounded (neutral) conductor in that panel. Your cord is a feeder and must be 4 wire. The fact that you don't wish to spend the money for a new cord does not change either the electric code nor the safety reasons for those code articles.

Any bar having a three wire, 240 volt circuit, supplying 120 volt loads needs to take a little of their profit and correct that violation.

I'm not trying to be the bad guy here, or rain on anyone's parade, but if someone gets hurt or killed, I'd would hate to hear "a licensed electrician told me this was ok." All of us look bad at that point.

I thought about just skipping this thread and letting it go, but I just wouldn't feel right having read it. So there is my 2 cents. For what it's worth.

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