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Thread: Wiring for a NEMA 14-50 outlet
03-01-2005, 01:45 PM #1jfsmith Guest
I am looking for a guide for what the correct wiring for NEMA 14-50 and NEMA L14-30 outlets are? Don't want to do this wrong and fry a machine, so I would rather ask if somebody know what the standards are?
03-01-2005, 02:36 PM #2
The 14-series are intended for use with 125/250VAC. The 14-50 will carry 50A, and the L14-30 indicates a locking (twistlock) device with a 30A rating.
You will have 4 screw terminals on the devices, 2 brass colored, one silver, and one green. The 2 brass screws are the 2 hot wires (usually red and black), the silver screw is the neutral (white wire), and the green screw is ground (green or bare copper wire).
03-01-2005, 02:52 PM #3
Assuming that you are wiring for 3 phase since you are using this series of twist locks, The ground will go to the green and one of each of the three phase leads will go to the other terminals. The "wild" three phase lead will go to the silver. If what ever motor you are running runs in reverse reverse the wires to the two brass colored screws.
03-01-2005, 03:42 PM #4
Using a 14-series receptacle for 3 phase power is a violation of the listing and labeling requirements (article 110.3B) of the NEC, and can be a VERY hazardous practice. For 3-phase 120/208 applications, look into the 18- or 21- series devices.
If someone plugs a device requiring the proper wiring into such a "bootleg" receptacle, they get fireworks and smoke if they are lucky, and a serious shock if they aren't. If OSHA or your insurance company finds about such an installation, the cost of buying the proper plug and receptacle will look like nothing.
03-01-2005, 03:46 PM #5
The L14-20/30 series of plugs/receptacles are not intended for three phase wiring. Yes you can wire them as suggested, but someone who is not careful could make the fatal assumption that the silver terminal is neutral. This series of connectors are designated as 125/250 volt, which means they can be used for either 125 volt, or 250 volt, single phase depending on need.
Yes, you can wire up a connector to single phase or three phase if you have enough terminals, but I recc against doing it for a lot of reasons.
Didn't type fast enough I see. [img]smile.gif[/img]
03-01-2005, 05:19 PM #6jfsmith Guest
This is single phase power from my new generator and with everything in the world, not all of my machinery (and plasma cutter) have the same plug or pig tail. So I need to know what is hot and what is neutral and what is ground, which I think N2 came close to the answer. I copied a page out of the manual and labeled the poles of the outlets, so can anyone figure out what is what?
And for a lengthy reason, I am not hard wiring all of this together, well not yet.
03-01-2005, 06:22 PM #7
Sorry about that.Got my NEMA numbers mixed up.
Suffering from CRS I guess.
03-01-2005, 08:38 PM #8
I have looked at an L14-20 and an L14-30 receptacle, which is the same as on your generator. They use the same wiring sequence.
#1 should be ground
#2 should be a hot leg
#3 should be neutral
#4 should be the other hot leg
*****Please verify yours are the same, by looking at the sides of the receptacle on your generator*****
Gold screws are hot and silver is neutral - green is ground.
Some of your equipment may not be wired for four wire power. You may only have two hot wires and a ground. In that case ignore the neutral when you wire the plug on the equipment. The two hot leads may be both black or one black and one red. It does not make any difference which one goes to which hot connection.
If you are using 125 volt equipment you can chose either of the hot legs to power the item. One hot, one neutral and one ground (black, white, green).
*********If you have any doubt about which connection is which color (gold-silver-green) take it out of the panel on the generator and verify it*********
Another easy way, if you have a simple voltage probe is to test each port on the receptacle. A simple one costs about $2.00 at the hardware store to test one leg at a time. Only the hot ones will cause the bulb to light. (with the generator running of course)
I do not have a 50amp receptacle to check and see which is which. They are likely the same sequence as the smaller ones, except the U shaped port is probably the ground. Again, you should be able to see what color wires goes to this receptacle and see what color the screws are.
03-01-2005, 09:41 PM #9
Assuming your drawing shows the "front view" of the female (receptacle) connectors, the pin assignments are as follows (numbering is yours):
A (NEMA L5-30R)
B (NEMA L14-30R)
C (NEMA 14-50R)
03-02-2005, 08:05 AM #10
This post made me rather anxious - I have a shop full of L14-30 being used for three phase. Fortunately, I am the only one in the shop and the plugs are carefully labeled as being three phase. I am also running off of a phase converter which is off when not in use. Still, I see the danger of a mistake and would like to do the correct thing.
One thing I am confused about is what all of the terminology means. I went to Leviton and came across this catalog page:
Leviton Catalog Page
Can someone explain what the difference between,
3-phase 250V 3-pole 4-wire grounding
3-phase Y 120/208V 4-pole 4-wire non-grounding
I assuming that Y means a Y connection with three phases and a common (in the middle of the Y).
I would assume that my three phase converter is putting out 3-phase 250V 3-pole 4-wire? It is a rotary converter adding a leg to single phase. So it would appear that I should be using L15?
I am significantly confused.
Also, I have a 3-phase transformer putting out 480 - it is on a different model plug (I forget which). What should I be using for that?
I am a little confused about the shock scenario. I would assume that a neutral that is "hot" with a third leg would look like a short. I would expect this to blow a breaker should it not? This has been my assumption about grounded wiring - that you design things so that inadvertent shorts are grounded.
03-02-2005, 09:21 AM #11
3-pole, 4-wire grounding devices would be used for equipment that does not require a neutral connection. They can be fed from either a wye or delta 3-phase system. The 3 phases and a ground wire are present on the 4 blades.
4-pole, 4-wire non-grounding devices are intended for use on a wye system, carrying the 3 phases and the neutral, but no equipment grounding wire. Definitely not a good idea for new installations, but sometimes seen on older equipment, particularly where the equipment is effectively grounded by other means (building steel, water piping, etc.)
Connecting a hot phase where a neutral should be will apply phase to phase voltage to any components that are connected between a phase and neutral. This will smoke electronics pretty quickly, and overheat contactor coils, etc. It also presents a shock hazard at the outer shell of lamp sockets or other places where a neutral is accessible. If the neutral is somehow grounded to the frame of the equipment (it shouldn't be, but occasionally is), you either get a short circuit with sparks and tripped breaker, or an energized equipment frame if there is no solid ground connection back to the source.
If your phase converter puts out 3 phase 240V, then the L15- would be the proper connector (3 phases and a frame ground). If you are carrying the neutral through to the machines, use an L21-series device (3 phases, neutral, and ground). The L21- is intended for 208Y/120V service, but 240V 3 phase with a neutral (from a phase converter)is non-standard and there is no connector specifically for this setup. I would go with the 5 prong L21s and label them at the receptacle as 240V.
The proper connectors for 480V 3-phase are the L16-(3-pole, 4-wire grounding),L19-(4-pole, 4-wire non-grounding),or the L22-(4-pole, 5-wire grounding)series. For 480 single phase, use the L8-series.
03-02-2005, 10:58 AM #12jfsmith Guest
I think your right about the configuration and the clearest on your answer.
Many thanks to all,
03-03-2005, 10:54 AM #13
Thanks for the info - I now think I get it.
FWIW, I found a nice bunch of information on the Leviton web site. It has wiring diagrams for different voltage, grounding, and phase scenarios and the diagram lists the proper plug/recepticle numbers.
Leviton Wiring Diagrams