Why the 120/240 split issue?

[MarcusOReallyus]

I am more than comfortable wiring the generator. I am just not familiar with some of the information I have read.

Then please stop being comfortable with wiring the generator. You are scaring us!

We'd feel better if you felt worse.

Let me ask this a different way. Why is this different than a commercial genset? When that is back feed it provides 120/240v without having to load balance. What component allows that?

There is no "component". It's a fundamental difference in function.


It's not just about having 240 volts. It's WHERE and HOW you get it.


Might help to forget generators for a moment and read up on normal house power, and how it's wired. You are concerned with how it works all the way from the transformer to the panel.

This might help:

http://www.allaboutcircuits.com/vol_2/chpt_10/1.html

 

[steelandcanvas]

I was hoping some of the more knowledgeable people here would be willing to share some of that knowledge. But thank you for your in put anyway.

That is exactly what you're getting.

 

[LuckyDog]

I am more than comfortable wiring the generator. I am just not familiar with some of the information I have read. Let me ask this a different way. Why is this different than a commercial genset?

Actually they are NOT different.

When that is back feed it provides 120/240v without having to load balance. What component allows that?

Your House Panel has circuit breakers on both legs. IF your home wiring were designed properly, there should pretty much be half of the house load on each leg. (Balancing act) BIG IF. Comerical Generators are built for General Public. (That is why there are 20 pages of safety and 2 pages for operation.) They are ONE TRICK PONIES. These are MULTI-FUNCTIONAL units - 1 phase, split-phase, three-phase.

There is no "component".

Might help to forget generators for a moment and read up on normal house power, and how it's wired. You are concerned with how it works all the way from the transformer to the panel.

This might help:

Single-phase power systems : POLYPHASE AC CIRCUITS

A lot (most?) of us here are ex-military. You are getting some of the best dad-gum advice and knowledge available (outside of signing up with Uncle Sam's Boy Scout Jambore and getting the MOS for the equipment).

This group IS concerned about your safety. Thicken your skin, read the links, and keep asking questions until you understand.

 

[dependable]

I remember it was discussed in a post a while ago that some of the 16b s or 701s were modified for 120/240 already. It is my understanding that if you connect voltage tester to L0 and L1 and get 120v and l0 and l2 and get 120v, then you have a neutral. Just checking that this is correct.

 

[storeman]

My post was based on no understanding of the mep-016. Thanks for the education. Now I know why I never considered bidding on one.
Jerry

 

[Isaac-1]

I remember it was discussed in a post a while ago that some of the 16b s or 701s were modified for 120/240 already. It is my understanding that if you connect voltage tester to L0 and L1 and get 120v and l0 and l2 and get 120v, then you have a neutral. Just checking that this is correct.

This is true, but there is a word of caution, if using a digital meter you may pick up inducted voltage when testing, a 120V test light is a better second confirmation of connection between the neutral and line.

Ike

 

[MarcusOReallyus]

This is true, but there is a word of caution, if using a digital meter you may pick up inducted voltage when testing, a 120V test light is a better second confirmation of connection between the neutral and line.

Ike

Anybody who does electrical troubleshooting with a test light only is asking for trouble.

Anybody who does electrical troubleshooting with a meter only is asking for trouble.



Excellent point, Ike. BOTH tools are needed, along with the understanding of what they are telling you.



Even when dealing with 12VDC, a test light can tell you things that a meter won't, and vice versa.

 

[glcaines]

You can also use a 1 : 1 transformer with a center tap to get the neutral and the 120 legs when 240 is fed into it. Also, make sure you know how to ground the generator. If powering your house, do not use a separate ground at the generator. The generator should be grounded via the house ground.

I highly recommend that you hire an electrician that knows generators!

 

[dependable]

Use a Klein solenoid voltage tester for basic wiring in shop and generator terminal lugs (in 120/240 mode). So the light, like the solenoid tester, uses some current that the digital meter does not? So am less likely to get a misleading voltage reading? Just trying to learn.

To clarify my last post the voltage selector switch would be in 240v mode. And the reading between L1 and L2 would be 240v.

 

[glcaines]

Use a Klein solenoid voltage tester for basic wiring in shop and generator terminal lugs (in 120/240 mode). So the light, like the solenoid tester, uses some current that the digital meter does not? So am less likely to get a misleading voltage reading? Just trying to learn.

The Klein voltage tester is a good one in my opinion. Nothing wrong with trying to learn - it's people that don't try to learn that are the problem.

 

[Ratch]

If powering your house, do not use a separate ground at the generator. The generator should be grounded via the house ground.

I've heard this debate rage, and I'm not sure what the final consensus is on it, or that I ever got a clear picture of the consequences of getting it wrong. NEC makes the ground at the genset conditional on other factors, doesn't it?

Doesn't it also depend on whether the center tap on the genset is connected to the ground lug or chassis, or lifted from it?

Can you flesh out the reasoning behind using the household main grounding?


I understand the potential differences of having non-bonded ground rods, just always like to hear it explained again.


Also, I don't know why, but there are at least 5 different ground rods/paths I've discovered on my house...

 

[MarcusOReallyus]

So the light, like the solenoid tester, uses some current that the digital meter does not?

Yes, a digital meter has a very high input impedance. Therefore, it won't put a load on a circuit. It will give a correct reading of voltage, but if there's no load on the circuit, the voltage under load may be quite different.

IMPORTANT POINT TO REMEMBER: AT ANY POINT IN A CIRCUIT, LOADED VOLTAGE AND UNLOADED VOLTAGE ARE LIKELY GOING TO BE DIFFERENT.

Sometimes very different.

So, if there is induced voltage on that circuit, it will read it, BUT, once you put a load on that circuit, the voltage will drop, likely down to virtually nothing (ground). Induced voltage (in a case like this) is usually NOT able to provide much current, so when a circuit is loaded, voltage drops. A lot.

SAFETY ALERT: PLEASE DON'T MISUNDERSTAND ME. INDUCED VOLTAGE ISN'T SAFE. IN SOME CASES IT CAN PROVIDE ENOUGH CURRENT TO KILL YOU.


Here's a personal example from the world of DC, but the principles hold true for AC:

http://www.steelsoldiers.com/cucv/95389-fuse-running-light-keeps-blowing.html#post1223503

 

[Metalflames]

I appreciate all of the information and once I have time to study up I will. Also i understand how important safety is. I should mention that I am just trying to get a clear picture and understanding before my brother gets to schooling me (commercial/industrial electrician). In the mean time I have an injector issue that needs attending before I can even worry about making power.

 

[bsorcs]

Thanks, folks. Yet another informative and illustrative thread. Special thanks for the useful links and the insights re military vs commercial sets. Here come another few evenings of study, and I haven't even been able to score a genset yet.

 

[steelandcanvas]

Also, I don't know why, but there are at least 5 different ground rods/paths I've discovered on my house...

The NEC changed that quite a few code cycles ago. Now, everything must be grounded at one single point, ie: phones, cable, satellite and electrical system. The reason for one grounding point is you don't want a ground fault to go to the next available ground with the least resistance. For instance if you lost your electrical service ground, and incurred a ground fault, you could have a high amperage current flow through your phone system, satellite receiver, cable box or TV. These devices will not tolerate a ground fault being passed through them.

 

[Grega]

What you probably want on you generator is 120/240 volt. There is not a place on your voltage selector for this but you can still get 120/240 with a modification On my Mep 016A generator, the only way to get 120/240 volt is to open up your control box, put the voltage selector to 240 volt. Then run a piece of #10 wire from LO to TB6, or the 6th spot on the terminal board. One is furtherest away and the 6th one is the closest to you as you face the gauges. Do not switch the voltage selector after you do this. I would assume your MEP016D would be the same.
__________________

 

[helomedic1171]

so, my understanding regarding grounding the genset and using it to power your house, was:

disconnect, cut, or add a switch to the wire from the N lug (L0, I think...) to the Ground lug, and then ground the genset as normal. this is to allow the DC portion of the generator to have proper ground, but allowed the AC portion to be grounded with/to your house electrical system with no crossover between the two.

Thoughts?

 

[212sparky]

Of you dont feel comfortable adding a neutral, you can get a 240 volt to 120 / 240 volt transformer and be good to go.