Connection to a generator - 3 prong plug ok

Is connecting a 10kw generator via a 6-50r. 3 prong plug to your house with in the national electric code?

No.

Generator has a grounding point on its frame

Can Jude that to be in code

Thanks

Can I use the grounding point on the gen frame to be within code

Thanks

The question is 220 or 120 volts? For 120volts you need 3 wires, 1 hot, 1 neutral, and 1 ground. For 220volts you need 4 wires, 2 hots, 1 neutral, and 1 ground.

A 6-50R plug is a 50 amp 250 volt plug commonly used for welders that gives me the full output of the generator

The question is can I use the bonded generator frame grounding lug to make the 4 the wire - ground connection - and and still comply with the NEC

SHORT ANSWER for 120/240 you need 4 wires NOT JUST 3,,,,,,,2 Hots, Neutral, Ground

LONG WINDED ANSWER

We have been through this ad nauseum on here many many times over including Billy Bobs NEC questionable answers and/or other answers that could get you (or a utility lineman) killed plus be major NEC violations.

NOTE check with LOCAL AUTHORITY like the Utility provider and any local inspection authority and do what they tell you over anyone here, including myself, they NOT US rule. If in doubt consult local trained competent professional electricians and engineers, dont risk a fire or your life based solely on any answers provided here, be they lay or professional, including yours truly !!!!!!!!!!!!

That being said, here is my professional albeit rusty on the latest Codes, advice BUT NO WARRANTY, CHECK WITH LOCAL AUTHORITY NOT ME OR ANYONE HERE

The answer in my opinion depends on 3 things:

1) Is the Genset configured as a "Seperately derived Source"

2) Is the Genset 120 volt ONLY or 120/240???

3) Are you going to use a 2 or 3 pole Transfer Switch (or system or plugs n cords etc) I.E. are you going to switch the Neutral GrounDED Conductor or not???????????????

If the genest is 120/240 volt single phase three wire,,,,,,,,,,AND you plan to use only a 2 pole Transfer Switch (IE you DO NOT switch the Neutral GrounDED Conductor),,,,,,,,,,,,AND at the Genset the Neutral GrounDED Conductor and the Equipment GroundING Conductor ARE NOT BONDED TOGETHER (or the connection is seperated if it were bonded at the factory as some are),,,,,,,,,,

YOU NEED 4 WIRES: Two Hot UnGrounDED Conductors
One Neutral GrounDED Conductor
One Equipment GroundING Conductor

IF ITS ONLY 120 VOLT SINGLE PHASE

YOU ONLY NEED 3 WIRES" 1 Hot UnGrounDED Conductor
1 Neutral GrounDED Cond.
1 Equipment GroundING Cond

a) Dont forget to UN BOND any Neutral to Case/Frame connection (like many from factory have) if you plan to only use a 2 pole Transfer Switch or other such switching (Utility versus genset) methods.

b) Dont forget to carry an equipment GroundING Conductor out to the Genset and bond it to the Case/Frame.

c) ABSOLUTELY USE A TRANSFER SWITCH OR SOME OTHER SORT OF LOCK OUT DEVICE OR SYSTEM OR METHOD SO THERES NO WAY POSSIBLE THE GENSET CAN BACKFEED THE UTIITY AND KILL SOMEOMNE

d) DO NOT JURY RIG ANY SORT OF PLUG THAT CAN HAVE HOT EXPOSED TERMINALS THAT CAN GET A BODY KILLED DEAD


SUMMARY

For 120/240 Volt and 2 Pole Xfer with Gensets Neutral and Case/Frame NOT BONDED 4 wires

For 120 volt,,,,,,,,,,,,,,,,,,3 Wires

Im sure I missed something, if so perhaps the other fine knowledgeable sparkies here can add to this......

John T Tooooo long retired AC Power Distribution Electrical Design Engineer and rusty on the latest Codes SO NO WARRANTY CHECK WITH LOCAL UTILITY AND AUTHORITY

As has been previously stated you must have the gen frame grounded AND have a proper transfer switch.

Great answer

The generator is a portable (on wheels) 10Kw generator with a 3 prong 6-50R plug that has a 250v 42 amp breaker. I would like to keep it considered as a "Seperately derived Source" but my 4 wire suggestion may change the classification.

The generator has a second 4 pole twist lock plug with a 250v 30 amp breaker

Want to get the full 42 amp - 10kw generator output.

I can skip the ground as the generator and main panel connect the G + N --- or --- connect the G + N in the cord connection from the generator to the house creating a total 3 G + N connections.

I would assume this is not compliant with the NEC

The 4 wire work around

Can I use the 2 hot + N from the plug and then connect the 4th (ground) wire to the frame of the generator (intended to be used for a ground rod) and be compliant with the NEC. This would keep the G and N seperate as the NEC wants. BUT is their something else in the NEC that prohibits this?

Sorry, I don't have access to the NEC code

Thanks

1) "The generator is a portable (on wheels) 10Kw generator with a 3 prong 6-50R plug that has a 250v 42 amp breaker. I would like to keep it considered as a "Seperately derived Source" but my 4 wire suggestion may change the classification."

If its a "Seperately Derived Source" then its just like the Seperately Derived Utility Transformer. Unless you ONLY use plug and cord connected equipment to onboard receptaces IT REQUIRES A GROUNDING ELECTRODE just like at the Utility Transformer where the Neutral GrounDED Conductor has a No 4 copper wire ran down the pole to a Grounding Electrode (Earth ground Rod). Therefore for use as a Seperately Derived Source, the Neutral is bonded to the frame/case which is also bonded to a suitable Grounding Electrode (like a driven rod i.e. whats called a a Made Electrode.)


2) "The generator has a second 4 pole twist lock plug with a 250v 30 amp breaker"

Its my best "guess" those 4 poles are Neutral, Ground, two Hots I've seen small cheap gensets where the Neutral to case frame connection is made inside the outlet receptacle! Not sure not being there how that outlet is configured, sorry

3) "I can skip the ground as the generator and main panel connect the G + N --- or --- connect the G + N in the cord connection from the generator to the house creating a total 3 G + N connections."

Im not sure I'm following what you mean, but heres what is needed if you use a Two Pole (NOT switched Neutral) Transfer Switch and do NOT use the Genset as a Seperately Derived Source"

a) At the genset DO NOT HAVE THE NEUTRAL BONDED TO THE CASE/FRAME (disconnect it if its that way now),,,,,,,b) Run 4 wires to the Transfer Switch (2 Hots, Neutral, Ground),,,,,c) The Utility and Gensets Neutrals are bonded together (often inside Transfer Switch but NOT also bonded to case/frame of switch),,,,,,,d) Run an Equipment GroundING Conductor from the main panels Ground Buss out to the case/frame of the genset and also the transfer switches case frame in order that all non current carrying metallic enclosures or motor or genny frames etc be connected to the equipment GroundING Conductor)

4) "I would assume this is not compliant with the NEC The 4 wire work around"

If you do it as I described above I believe IT IS INDEED NEC COMPLIANT. It takes 4 wires,,,,No Neutral to case frame bond on genset,,,,,,Case frame of genset is bonded to equipment GroundiNG Conductor ran out from main panel,,,,,,Two Pole (NON switched Neutral) Transfer Switch,,,,,Utility and Genset Neutrals tied together

5) "Can I use the 2 hot + N from the plug and then connect the 4th (ground) wire to the frame of the generator (intended to be used for a ground rod) and be compliant with the NEC. This would keep the G and N seperate as the NEC wants. BUT is their something else in the NEC that prohibits this?"

I am too lazy to look that up but DO NOT LIKE THE SOUND OF IT I always routed all the conductors, including GroundING Conductor, in the SAME raceway or enclosure or cord or conduit etc. Thats a question one of the currently practicing professional electricians (NOT untrained Billy Bob) might answer better then me, it just been too long since I retired, sorry, but you have the 4 wires part CORRECT, I'm just leary of the Equipment GroundING Conductor being all alone and speperate lol but hey it may be okay IM JUST UNSURE

John T

All depends how many innocent people you want to kill. You need a properly installed transfer switch. Talk to a local electrician. Then pay him to do the job.

Change the generator to a 120/240V 50amp four prong twist lock.

John T

Possibly one of the best responses I've read on this or any other site/forum.

Good solid advice

for the others that simply say be compliant --- the transfer switch on the house side is a properly installed NEC compliant 4 wire setup. The problem is that the generators full out put comes from the 3 pole plug.

The 30A 4 wire twist lock is fully NEC compliant --- problem is it's only got 3/4 of the generator output.

I'm trying to figure out a way to get the full generator output to the house

Perhaps I need to explore the possibility of retrofitting the 3 pole 50A outlet on the generator to a 4 pole 50A outlet on the generator.

Not sure what implications that has. Didn't want to tear into the generator when I could have come up with a safe and NEC compliant workaround with the cables(s) connecting it to the transfer switch.

When I hear the word back feed a question comes to mind.When the power goes off there are a lot of loads sitting there.Could a 5k generator do anything but stall if 3 houses were connected to it.In the village there are 3 or more houses on 1 transformer secondary.My house and and my neighbors are on the same transformer.Next transformer has a house, church and school house on the same tranformer.My Dad worked for the electric co for most of his working life.Line men treat all lines as hot.I have watched linemen put short circuits on a line they are working on.When the power comes back on it take 3 tries before it works.Could you back feed a powerline with a 5k generator.I did get a chance to see a helicopter string line on a new power line.The pilot is pulling a light line but is still tethered to the ground.Wish my dad was here to see it.I have a photo of him hitching trees to a bulldozer when they cleared a hiline right of way in the late 30s.

Unless there is a single transfer switch common to all three services.
A single 5kW would run the lights and two plug in motor loads in total. As long as both motor loads are not on the same line.
The quick answer is no, don't waste you time, money and lineperson's safety trying.