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Generator wiring - neutral/ground

bgaidan

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PO had an outlet outside for a generator connection. It's a 3-wire, 50 amp plug. The generator I'm borrowing from work has a typical 4 wire 30-amp twist lock plug. What's the most correct way to wire this? Bond the neutral/ground? Or just use one?
 
So, the generator is only providing 240V and not any 110V?

Just use the two hots and ground. Grounds and neutrals are only tied together at the incoming service panel.
 
So, the generator is only providing 240V and not any 110V?

Just use the two hots and ground. Grounds and neutrals are only tied together at the incoming service panel.

It'll be feeding the main panel to power the 220v well pump and a couple 110v lighting and outlet circuits. Since the ground/neutral is bonded in the panel, I'm not thinking I'd want to feed the neutral since the panel already has a direct ground.


My old place had a 20kv set with an auto transfer switch. The new place, not so much. We have a nasty ice storm coming tonight so this is just a quick solution to keep some lights on. I plan on doing something a little more permanent. I'm expecting the power to be off for at least a few days this time around.

We had a fairly light ice storm last friday night and the power was off form 8am saturday until 6pm sunday. I was not prepared.
 
Is there a transfer switch in this contraption?
Just use 2 hots and a ground. no need for neutral if not using 120v
 
Is there a transfer switch in this contraption?
Just use 2 hots and a ground. no need for neutral if not using 120v

There will be 120....I'm feeding the panel to feed both legs, which will have the lighting and 120 outlet circuits on them.

No transfer at this point. Suicide cord and the main will be off.
 
You will need to see if your generator bonds the neutral to the frame of the generator, or if it has a floating neutral. It should state that near the plug on the generator. This will let you know the correct way to connect it. You should never bond the neutral twice.
 
PO had an outlet outside for a generator connection. It's a 3-wire, 50 amp plug. The generator I'm borrowing from work has a typical 4 wire 30-amp twist lock plug. What's the most correct way to wire this? Bond the neutral/ground? Or just use one?

Unbonded at the genset, ground genset case to driven rod.
 
I'd just twist the ground and neutral together in the 3 prong plug
but I don't have any sorta GFCI stuff that might dislike that, and they're all (n and g) on the same busbars in the panels anyways
 
[486 said:
;n315047]I'd just twist the ground and neutral together in the 3 prong plug
but I don't have any sorta GFCI stuff that might dislike that, and they're all (n and g) on the same busbars in the panels anyways

That could functionally work, but its not really safe. you'd be passing all the neutral current through the ground conductor and you could end up with ground not being 0 at the generator during steady, but unbalanced state - meaning more load on one leg than the other. We're not talking bus load of blind nuns level danger here, but the generator could bite you, and it is a thing that happens.

I would prefer a solution that involved a 4 wire connection, even if that meant jacking into a dryer/range outlet instead or even wiring up a highly non-compliant adapter with a twist lock plug on one end and the other end stabbed directly into the panel through a breaker, allowing for the neutral and grounds to go where they belong - I perceive this to be less work than unwiring shit at the borrowed generator.
 
I agree with the ground rod but why not have them together at the source?
They are tied together at the transformer which is out of the circuit now.

Technically the ground doesn't start until your service disconnect - normally you establish your grounding conductor between the meter and the service disconnect, most commonly in the panel with your main breaker. That grounding jumper (which is normally a green screw in a neutral bar) is the connection you don't want to duplicate.

At the transformer the utility grounds their system neutral and they normally tie the center tap of the low side to it to establish the two legs. Notice on a normal house service there are only 3 wires to the weatherhead, L1, L2 and Neutral, but after the service disconnect or sometimes the meter, there are 4 because the grounding conductor has now been established.

If you ground the neutral at the generator, then it is a separately derived system and you are supposed to use a transfer switch that switches the neutral conductor so that funky neutral things from your generator don't effect the utility neutral. Also have to follow article 250 and pound ground rods.
 
That could functionally work, but its not really safe. you'd be passing all the neutral current through the ground conductor and you could end up with ground not being 0 at the generator during steady, but unbalanced state - meaning more load on one leg than the other. We're not talking bus load of blind nuns level danger here, but the generator could bite you, and it is a thing that happens.

I would prefer a solution that involved a 4 wire connection, even if that meant jacking into a dryer/range outlet instead or even wiring up a highly non-compliant adapter with a twist lock plug on one end and the other end stabbed directly into the panel through a breaker, allowing for the neutral and grounds to go where they belong - I perceive this to be less work than unwiring shit at the borrowed generator.

Pretty much what an electrical PE friend of mine said to do - bond the neutral and ground at the plug and try not to overload a single leg. If I can find the ground rod for the house, I may be able to just run a ground directly to that from the gen.

No option for a drier or range plug here. It'd be 100'+ run to do that. I could pull the cover and hard wire it to a breaker, but there's really not a great way to get a cable inside to the panel at the moment. The PO wired this 3 prong outlet off the back of the house for a generator, but obviously didn't know what he was doing. I haven't been here long enough to start unfucking things, but the weather doesn't care about that. The good thing is that it's right near the panel so I can probably pull a new length of cable and put a more correcter outlet there fairly easily, just not at the last minute like this. But I'm also fairly convinced I need to get a 22 or 25 kv whole house setup like I had at my last place and not fuck with this temp shit. Already have a 350 gal lp tank to feed it.
 
Agreed you should have a four-wire setup if you want 120v.
 
I run mine through a 3 prong 50A plug, 2 hots and a ground. Neutral bonded in the panel takes care of all that. There is also a ground stake right outside from the panel also.

I should probably run a wire from the ground stake to the frame of the genset.
 
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I run mine through a 3 prong 50A plug, 2 hots and a ground. Neutral bonded in the panel takes care of all that. There is also a ground stake right outside from the panel also.

I should probably run a wire from the ground stake to the frame of the genset.

I noticed the borrowed generator has a note that "neutral is bonded to the frame" or something like that so I'm pretty comfortable in the way I built my cable for the time being. I did find my panel's ground wire outside and if I had the proper lug on hand, I'd probably go ahead and tie the generator to it, but I don't so I won't.
 
Pretty much what an electrical PE friend of mine said to do - bond the neutral and ground at the plug and try not to overload a single leg. If I can find the ground rod for the house, I may be able to just run a ground directly to that from the gen.

No option for a drier or range plug here. It'd be 100'+ run to do that. I could pull the cover and hard wire it to a breaker, but there's really not a great way to get a cable inside to the panel at the moment. The PO wired this 3 prong outlet off the back of the house for a generator, but obviously didn't know what he was doing. I haven't been here long enough to start unfucking things, but the weather doesn't care about that. The good thing is that it's right near the panel so I can probably pull a new length of cable and put a more correcter outlet there fairly easily, just not at the last minute like this. But I'm also fairly convinced I need to get a 22 or 25 kv whole house setup like I had at my last place and not fuck with this temp shit. Already have a 350 gal lp tank to feed it.

A 350 gallon tank is going to run a 22kw generator for about a week or less. FYI. Run times on big genset is nuts. We were going to do a similar size generator but when the panic is done will probably do a 15-17kw gen set because it will us a lot less propane. But I will probably end up with a manual transfer and start system of a smaller system.
 
Technically the ground doesn't start until your service disconnect - normally you establish your grounding conductor between the meter and the service disconnect, most commonly in the panel with your main breaker. That grounding jumper (which is normally a green screw in a neutral bar) is the connection you don't want to duplicate.

At the transformer the utility grounds their system neutral and they normally tie the center tap of the low side to it to establish the two legs. Notice on a normal house service there are only 3 wires to the weatherhead, L1, L2 and Neutral, but after the service disconnect or sometimes the meter, there are 4 because the grounding conductor has now been established.

If you ground the neutral at the generator, then it is a separately derived system and you are supposed to use a transfer switch that switches the neutral conductor so that funky neutral things from your generator don't effect the utility neutral. Also have to follow article 250 and pound ground rods.

We already beat the transfer switch horse to death so I’m not going there.

But in reality the ground starts at your X2 bushing at the transformer by connecting to the pole ground and your bare tri-plex neutral. I believe the RECs hook the primary neutral to the X2 which is tied to your pole ground.

The driven ground rod is the service ground and you hope stays grounded and hope you don’t have to depend on the pole ground as the only ground for the service if something happens to the ground rod.
Now we have two grounds for the service that can have a potential difference but we still do it for safety.
Some of us has seen the the neutral come loose at the X2 bushing, the #6 piece of copper going to the service ground get broken, and the voltage on the 110 leg at the house measure 200 VAC.

My point is grounds and neutral common at the source is normal and it doesn’t effect the ground fault circuits.

To qualify check your T4, T5, T6 leads on a 3 phase utility sized generator. Ground and neutral are common.
 
A 350 gallon tank is going to run a 22kw generator for about a week or less. FYI. Run times on big genset is nuts. We were going to do a similar size generator but when the panic is done will probably do a 15-17kw gen set because it will us a lot less propane. But I will probably end up with a manual transfer and start system of a smaller system.

The 20kv at my old place I think was rated under 3 gal/hr at full load. You're never going to be running it at full load, but they'll size it for startup. I ran it for nearly a week after the tornado in '17 or '18 and I was under a half tank when it started and I didn't run out. Biggest draw on that system was the AC/heat pump. Had a gas WH and a freestanding gas log that was more than adequate to heat the place, so running it in the winter I really wasn't putting much load on it. And you don't HAVE to have A/C in the summer if you're trying to preserve gas.

I don't think there's a huge difference in burn rates at idle or at similar loads between say a 20kw and a 14kw unit....or at similar loads.

The automatic transfer wasn't necessary, but it sure was nice. Power goes off in the middle of the night, 40 seconds later the generator has started, switch is thrown and the power is back on.

The new place has two HVAC units so I'd either have to come up with a way to automate shutting one or both off in the event of an outage and the generator running.
 
Maybe i missed it. How are you planning to connect the two different receptacles together?

I vote this:

I would prefer a solution that involved a 4 wire connection, even if that meant jacking into a dryer/range outlet instead or even wiring up a highly non-compliant adapter with a twist lock plug on one end and the other end stabbed directly into the panel through a breaker, allowing for the neutral and grounds to go where they belong - I perceive this to be less work than unwiring shit at the borrowed generator.

Cut the end off the generator cord and put it under the 50amp breaker. If it's too short, buy some 10/3 grounded romex and extend it 100ft if you need to.

Or if you can find the right twistlock receptacle, put it in a box on the end of the 10/3 romex bugged into the panel and run that outside to the generator temporarily.
 
Another vote for 3-wire suicide cord and ground rod at the gen-set.
 
Maybe i missed it. How are you planning to connect the two different receptacles together?

I vote this:



Cut the end off the generator cord and put it under the 50amp breaker. If it's too short, buy some 10/3 grounded romex and extend it 100ft if you need to.

Or if you can find the right twistlock receptacle, put it in a box on the end of the 10/3 romex bugged into the panel and run that outside to the generator temporarily.


This is the final product. The neutral and ground from the 4-pin plug are bonded to the ground on the 3-pin plug.


Honestly, since neutral and grounded are bonded at the generator AND in the panel, I don't see any problem with this, other than the short run from the outlet to the panel will be combined (which is under 2').

Someone better call dibs on my shit quick!:flipoff2:
 
Honestly, since neutral and grounded are bonded at the generator AND in the panel, I don't see any problem with this, other than the short run from the outlet to the panel will be combined (which is under 2').
Someone better call dibs on my shit quick!:flipoff2:

oh noes NEC says you're gonna die a lot and the fire department is gonna laugh at your proudly displayed furry porn

just choose to go with a '90s version of NEC and you're 100% up to code, separated grounds is a very recent thing
 
[486 said:
;n315650]separated grounds is a very recent thing

I've got a total of 6 ground stakes in my system. Every panel/sub panel and CNC machine gets one. You can never have to many grounds.
 
I've got a total of 6 ground stakes in my system. Every panel/sub panel and CNC machine gets one. You can never have to many grounds.
I've got many as well
mainly because I've got a fuckton of panels and sometimes hammering in a ground rod is a lot cheaper than running a ground conductor back to the previous box
another fun thing that used to be normal but now is going to kill everyone ever

actually, used to be that you'd run one fuckin' wire and a ground stake
if you couldn't get enough juice you'd dump some salt water on the ground rod
 
We had a fairly light ice storm last friday night and the power was off form 8am saturday until 6pm sunday. I was not prepared.

And just wtf were you doing monday morning? Waiting for the next storm rather than stopping by Home Depot to get the fix supplies? Way to procrastinate. Your grandfather would be highly disappointed.




:flipoff2:
 
This is the final product. The neutral and ground from the 4-pin plug are bonded to the ground on the 3-pin plug.


Honestly, since neutral and grounded are bonded at the generator AND in the panel, I don't see any problem with this, other than the short run from the outlet to the panel will be combined (which is under 2').

Someone better call dibs on my shit quick!:flipoff2:

I was going to PM you and ask for your SS number so I could take out a life insurance policy but I believe your good.
Send it until the blue smoke leaks then start another thread we can jack
:smokin:
 
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