Generator Twistlock Question

Getting ready for the storm here and had the house panel upgraded last year to 200 amp service. With this, I got a interlocked transfer switch for the generator that has a box with a 4 prong L14 30 amp plug. The genset has a 3 prong L6 30 plug. What am I hooking the locking lug to at the house end? Ground or neutral?

You need to use the neutral.

Phil May wrote:You need to use the neutral.

Just got off the phone with the electricaian, he said to use the neutral but would probably work either way as the neutral buss is grounded in the main panel.
Thanks guys.

probably work either way as the neutral buss is grounded in the main panel.

I think thats bad advice, use the neutral. For reasons like not bonding the ground in a sub panel, if the neutral fails the ground becomes the neutral, thats not a good thing from what I understand.

But with that said I do not know what kind of set up you have..

When I wired it right to the panel, I always used the neutral buss. Reading the 3 wire plug on the genset, the locking lug is green on the plug but is really a neutral in this case as the genset has no ground.

Yeah, I think your good to go..

I'll preface this by saying, I'm not an electrician and most definitely not qualified to give advice. Based on what I have read, you need four conductors from the generator to the service panel for a 120/240 connection. Two hot legs, neutral & ground (or more appropriately a bond to the service panel). Additionally the bonding strap on the generator should be severed & the generator should not have its own ground rod. If the three conductor outlet is either 120 volt only or 240 volt only, three conductors will suffice. Either hot neutral & bond for 120 volt or two hot plus bond for 240 volt.

If the generator is later used as a portable, the bonding strap should be reconnected and the generator properly grounded.

I have seen these hooked up a couple different ways by licensed professionals and they passed inspection, so what do I know.

Obviously you should consult a qualified electrician in your area for actual advice.

Never used a ground strap on a generator, even when I was working in construction (industrial roofing). But I was never one to follow the rules - as long as it worked.

top top wrote:I'll preface this by saying, I'm not an electrician and most definitely not qualified to give advice. Based on what I have read, you need four conductors from the generator to the service panel for a 120/240 connection. Two hot legs, neutral & ground (or more appropriately a bond to the service panel). Additionally the bonding strap on the generator should be severed & the generator should not have its own ground rod. If the three conductor outlet is either 120 volt only or 240 volt only, three conductors will suffice. Either hot neutral & bond for 120 volt or two hot plus bond for 240 volt.

If the generator is later used as a portable, the bonding strap should be reconnected and the generator properly grounded.

I have seen these hooked up a couple different ways by licensed professionals and they passed inspection, so what do I know.

Obviously you should consult a qualified electrician in your area for actual advice.

I talked with the electrician, he said use the neutral (this is how I have always wired it to the panel) The generator is a 3 prong and has no ground.

Neutral and ground go to the same place ultimately from the way I view it in my breaker box. Seems like either would work to me. I don't claim to be an electrician either lol. Just make sure the hot wires are going the right way

Lightning wrote:Neutral and ground go to the same place ultimately from the way I view it in my breaker box. Seems like either would work to me. I don't claim to be an electrician either lol. Just make sure the hot wires are going the right way

There are only two hots and a ground coming from the pole. The neutral only exists from the panel to the load if I see things correctly.

From OSHA:

Thus, rather than connect to a grounding
electrode system, such as a driven ground
rod, the generator’s frame replaces the
grounding electrode.
If these conditions do not exist, then a
grounding electrode, such as a ground rod,
is required.
If the portable generator is providing electric
power to a structure by connection via a
transfer switch to a structure (home, office,
shop, trailer, or similar) it must be connected
to a grounding electrode system, such as a
driven ground rod.

Ref: https://www.osha.gov/OshDoc/data_Hurricane_Facts/ ... erator.pdf

People get confused because "Portable generators don't require a ground" Actually, they do. The FRAME is the ground. So if you have it up on wheels, sitting on wood, plastic, etc and it is no longer a ground, you do actually need one.

Same question comes up all the time with campers who boondock. Only there, an improperly grounded generator coupled with an electrical defect or fault can cause "hot skin" where the frame and aluminum skin of the camper can become electrified.

Do you need to drive a rod into the ground or use some other means of grounding (since the frame is considered "good enough")? It DEPENDS

3 wire 240 volt generator outlet has NOT a neutral.
Can it be gotten around? Yes, but only by non acceptable means.

It requires 4 wires to have 120/240 volt beyond a service entrance panel.
Ignore all this if you dare.

BTW:
A ground conductor is a "non-current carrying conductor"
A neutral conductor is a "current carrying conductor"
They may be bonded at one point only.

coaledsweat wrote:

Lightning wrote:Neutral and ground go to the same place ultimately from the way I view it in my breaker box. Seems like either would work to me. I don't claim to be an electrician either lol. Just make sure the hot wires are going the right way

There are only two hots and a ground coming from the pole. The neutral only exists from the panel to the load if I see things correctly.

Think of Neutral in a single phase system as the "Working Ground." It is what is normally used for power to flow in 120v systems. Is it grounded? Yes, unless it "hands off" it's ground to another box/location (unbonded ground/neutral box)

The Ground in cords is actually a redundant safety. Think of it as "Backup Ground" or "Environmental (shock prevention) Ground" (like static, different circuits, defective load, etc.

"Earth Ground" is your electrical system's anchor. It draws power from your electrical provider by ensuring a proper voltage differential between supply and your system (=potential/voltage). It ALSO provides a drain for excess, stray, or misdirected power (think electrical short, builtup charge from static or other source, etc)

Electricity doesn't just want the easiest path, it wants the most drain to Earth. You are only harmed if power flows THROUGH you (okay, ignore plasma and other special circumstances, this is very basic).

Where does power flow through you? To Earth or other ground, but only if you have a higher potential than it. If you are ZERO and the power is not, it flows through you to get ground. Of course, copper wire is a better conductor than we are, so it flows through the cords instead.

Unless you make yourself more attractive to the voltage by being a better ground than the (broken, miswired, defective, etc) wire, then it flows through you.

The ultimate goal is to have a PERFECT earth ground and have every single item perfectly connected to that point. But sometimes that isn't possible or practical, such as portable generators. The power they produce and just their portable nature make the likelihood of something going wrong pretty high, so it is wise to provide for emergency, backup, secondary earth ground, such as the frame or grounding rod, device, etc.

See how this related to 240V.

Think of leg 1 as 120 degrees Clockwise, leg 2 as 120 degrees Counterclockwise. When they are used for power together, power flows from 120 Clockwise, through Zero (but no where to get off in a 240V device), so it must continue to 120 Counterclockwise to get off the train. That makes 240 volts. If there is a stop in the middle (ground/neutral) at Zero, it jumps off there instead to make 120 volts.

For 120 volts, your electrical box usually alternates between CW and CCW (left and right, Leg 1, Leg 2, whatever you want to call it).

Guess what happens if the power is coming from a Leg, from 120 volts headed to zero and YOU are sitting at 50 (meaning you have a ground connection equal to or better than the wiring)? It jumps off at your stop and streaks to YOUR GROUND (through you!). Wouldn't be a problem if it didn't burn and overload everything along the way, or interfere with other "important" electrically driven items in your body

In a generator supplying a house, you WANT the power to flow through the house's Neutral (Working Ground) to supply power. In a perfect world, no problem. But you are wise to have a Backup/Emergency Ground at the generator to be absolutely sure it's entire system (ground, frame, etc) stays at the exact same potential as the house's, being Earth Ground.

Ever see a generator running in the back of a pickup with a bed liner? Stand in there all day with it, even if it malfunctions and you are fine. Unless you are standing on the wet, muddy ground, holding your shovel, bar, whatever and reach over to turn it off or slide it back from where it vibrated to, then BAM! Dead man standing

Portable generators are notorious for building up stray charges. They get cheaper and more disposable all the time. Drain them before they build up (earth ground) and you're fine.

So for everyone, be careful with portable generators as you set them on wooden pallets (poor or ungrounded), back your bed lined pickup to the basement door and run generator from the bed, and any other situation (outside, vented enclosure with a floor?) that prevents the frame from being a good ground.

Hope this helps a bit.

McGiever wrote:A ground conductor is a "non-current carrying conductor"
A neutral conductor is a "current carrying conductor"
They may be bonded at one point only.

LOL, took me 2 pages to say that!