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another generator question

Posted by woodturner79 (My Page) on
Fri, Nov 9, 12 at 9:14

first off, I do have a mechanical transfer switch to open my main breaker and close the generator breaker on the panel. This is also my main panel so the neutrals and grounds are all bonded together (that might make a difference?) There is no possible way I could run my backup generator without opening the main so there isn't a concern there. Also there are no "suicide" cords being used and the proper inlet is installed (4 prong). Just want to get that out of the way.
Now onto my actual question. The house had all these things already installed. I never used it because I never had a generator and didn't really see too dire of need to get one.
Recently though someone owed me some money and couldn't afford to pay, so they settled the bill by giving me a generator. Now that I have one I'd like to be able to use this system if the power goes out. The generator is older but runs very well. It has one 120V receptacle and one 240 receptacle.
However the 240 receptacle is just that, 240. It is not 120/240 (just a straight 20 amp 240). If I use this and don't carry a neutral with it, what exactly will happen?
Can I carry a neutral off the 120V receptacle and use that? It wouldn't be hard at all to open the generator take out the 240 receptacle and install a 4 prong 120/240 one (after running a neutral off the 120 receptacle first of course). I need it to be 120/240 though for my well, which is 240, and some general lighting circuits (120).


Follow-Up Postings:

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RE: another generator question

It would depend on the generator model.


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RE: another generator question

it's a Coleman Powermate 5000 watt (model PM0525202).
I'm confused why the model would make a difference though? My question is if I need to worry about carrying a neutral when using the 240 receptacle to power my panel or not.


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RE: another generator question

If the generator is not large enough to carry the entire panel load it cannot automatically be switched in.

That is one of the reasons for smaller sub-panels for generator power.

The subpanel does 'load shedding' by only switching in up to the generator's capacity.

If an automatic switch over could overload the generator it cannot be installed that way (auto switch the entire large panel).


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RE: another generator question

The two manuals for that part number I've looked at show a double 120v receptacle and a single 240v 4-prong receptacle.

You're saying you have a single 120v receptacle and a single 3prong 240v receptacle?


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RE: another generator question

by your logic brickeeye, people need generators able to handle full 200 amps then if its in a 200 amp main panel? Get a clue man.
His set up is very common in houses around my area. People use whatever size generator they want and they backfeed in and turn on and off whatever circuits they want


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RE: another generator question

"You're saying you have a single 120v receptacle and a single 3prong 240v receptacle?"

Yes there is one, run of the mill 3 prong (hot, neutral, ground) 120V duplex receptacle. Below that there is one 240V 3 prong (hot, hot, ground) 20 amp duplex receptacle. I am aware that the PM0525202.02 and PM0525202.03 have a 4 prong 120/240 outlet, mine does not. It is just the PM0525202 model I guess.
Once again, my question is, do I need to carry a neutral from the generator to my inlet, or is carrying the 2 hots and a ground sufficient since a neutral is already established in the panel and all the grounds and neutrals are bonded together?
I'm not trying to be snarky. This installation was done and inspected when the house was built. It is installed properly and is safe. The main breaker has to open before I can close the breaker that the inlet feeds. I'm well aware I can't exceed 20 amps of load, and the breaker to the inlet goes to is 20 amps. I'm well aware how the system works I simply am just asking if I need to take a neutral from the generator??


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RE: another generator question

this is not a picture of my actual generator, but this is exactly what is looks like. The upper outlets are the 120V the lower ones are the 3 prong 240 ones.


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RE: another generator question

Due to it's construction, it may be difficult to access the electrical connections, and without seeing a schematic of the wiring to know for sure, it does appear like you may be able to install a 20 amp L14-20R twist-lock receptacle, to the generator.

Yes, you need the neutral, directly from the generator winding junction not just tapped off one of the 120 volt outlets. Use all 12ga wiring for the two legs, neutral, and ground.

While there is nothing to prevent you from modifying equipment for your own use, you still want to do it safely and within commonly accepted industry standards. And test it all first with a voltmeter and then external loads before attempting to connect it to a properly installed transfer switch power inlet.


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RE: another generator question

It depends on model as some generators do not have a center tapped 240. You get the choice of either 120 or 240 but if you attempt to boot a neutral from the 120V receptacle you're going to get the same leg as one of your 240 legs.


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RE: another generator question

According to the manual I have for that model, it has a L14-20R on it which has a neutral.


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RE: another generator question

mine doesn't have a twist lock. Just the straight three prong 240. NEMA 6-20R I think? I think maybe they only produced it for a short while and then went to the .02 and .03 models in which they did put in the 4 prong twist locks.

if I meter between the two hots of the 240 outlet one at a time, to the neutral of the 120v outlet and get 120v on both of them, I should have the center tapped 240 like you described right? If it's not I would get 120v and then 0 in which case I'm totally out of luck?


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RE: another generator question

"by your logic brickeeye, people need generators able to handle full 200 amps then if its in a 200 amp main panel? Get a clue man.
His set up is very common in houses around my area. People use whatever size generator they want and they backfeed in and turn on and off whatever circuits they want "

If you want to comply with the NEC (and not kill generators) and have automatic crossover (as opposed to manual) you must have a generator large enough to carry the entire load under the NEC.

That is why all the systems you see for sale come with a separate smaller panel.
The smaller panel is what the generator feeds, and IT can automatically switch over since all the other loads are shed.

It is the automatic crossover that requires you to have a large enough generator.

If you have to go out and manually connect the generator, it is obviously not automatic.
Before you even try to start the generator you better have shed a bunch of loads by turning off the breakers in the panel to get withing the generator's capacity.

You are the clueless one, and dangerous also.


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RE: another generator question

"If you want to comply with the NEC (and not kill generators) and have automatic crossover (as opposed to manual) you must have a generator large enough to carry the entire load under the NEC."

where in my posts did I ever say I had an automatic switch? I manually open the main breaker, which in turn closes the inlet breaker through a mechanical link. I thought I was very clear about the setup I have. I know at least two other people with the exact same setup. Maybe if I type all in caps? I CAN NOT HAVE THE BREAKER THAT THE GENERATOR INLET FEEDS CLOSED WITHOUT FIRST OPENING THE MAIN, AND THE BREAKER THAT IT BEING BACKFED IS SIZED PROPERLY. I AM WELL AWARE I CAN NOT EXCEED THE GENERATOR'S WATTAGE.

Why is no one actually addressing my questions? Opps let me try that again....
WHY IS NO ONE ACTUALLY ADDRESSING MY QUESTIONS?
I'm not re-inventing the wheel here.


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RE: another generator question

woodturner79,

The quotes in your last post refer to a disagreement between hexus and brickeyee - nobody was suggesting that is what you were doing.

One the other hand, I "did" address your question and suggest what you need to do to make this generator capable of hopefully meeting your needs to run your 240VAC well pump and 120VAC general lighting circuits. Was it not just what you wanted to hear?


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RE: another generator question

With one 120v "outlet" both receptacles are on different legs so if possible the load needs to be balanced across these two just like on the 240v plug.


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RE: another generator question

yosemitebill -
My question is if I have to take a neutral through my cord to my inlet to backfeed into my panel. I realize you simply said yes I do have to, but there's more to this I suspect since this is my main panel and all the grounds and neutrals are bonded together. If there's a fault, it would go back to the source (generator) through the ground anyway correct? Why carry a neutral if I don't have to? Why do you say I have to?
Another major thing I just found out today is that the generator neutral is bonded to ground. So carrying a neutral and ground from it would potentially have my ground and neutral running in parallel, would it not?


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RE: another generator question

Since you have a mechanical crossover you are free to forget to perform the needed load shedding by switching off breakers before switching on the generator feed through the interlock.At least it sonds lie you have an interlock.

Usually it just blows the generator output breakers.
Sometimes it also damages the cheap electronics in the generator.

No breaker is fast enough to protect electronics.

"Can I carry a neutral off the 120V receptacle and use that?"
You can try, and hope nothing blows in the house with a (likely) unbalanced 240 V split phase system.

Instead of 120 V/120 V legs summing to 240 V you will get a random pair of voltages on the legs that sum to 240 V, but that also depends on how the generator output is fed, and even what loads are preset.

A very few generate only create 240 V and then use a transformer to create the 120/240 v split phase used in residential systems, but even these require a connection to earth ground and the house neutral.

You also need to remove any neutral to earth tie in the generator since they are already tied in the main panel.

Just because you (and possibly hundreds of your neighbors) have 'rigged' something that appears to work does not make it safe or compliant.
I have seen AHJs miss the ground -neural bond in almost every small generator that must be removed if you feed a residential panel.

They do not know enough about how generators are buit to even recognize the bond is preset from the manufacturer.


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