Generator Load balancing

Electronics
#1

How much of a problem to keep your loads balanced on a 240V generator that supplies multiple 120V loads and some 240V loads?

I’m just doing some thinking. I just installed an relatively cheap generator onto an area with loads as above. I am planning to upgrade the generator when I can but now it is 3500 KW and can just drive my 120V loads and 240V well pump x 2. That is, just about everything else that is 240V would likely put it over the rated amperage or wattage.

I have a huge transformer, 30 KW, that I can experiment with and it has some taps that would give me a 2:1 ratio for step up or down. It should be pretty efficient, I’m guessing, as it weighs 350# and the turns are really big copper.

So I got to thinking . . . wouldn’t this balance my loads? See pic below.

  • Drive 240V stuff with 240V from the generator
  • Drive 120V stuff with 120V from stepped down 240V
  • Link the neutrals
  • Isolate the loads from the original panel

This arrangement would have to be tapped off the breaker outputs and into separate breakers I guess since driving all 120V loads would involve electrically tying all the 120V hots together whether they came from L1 or L2 of the original house panel.

I have driven all 120V loads with a single 120V generator before by tying together L1 and L2 and it works well. But, of course with L2 and L2 tied together you can’t drive anything that is 240 without isolating it from the panel. (or keep the 240’s on the panel bus and isolate the 120’s)

Aside from the fact that

  • The whole thing is not close to any code!
  • I would have to double lug some of the circuits (or create an entire separate wiring panel)
  • The thing may be impractical in terms of the amount of work, components and wiring
  • It would lose some efficiency through the transformer

Does this look like it would work?
Anyone have experience or stories about balancing issues?

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#2
#3

I love the Honda inverter generators. They are top notch. Parallelling them gets you double the amperage but generally not double the voltage since the voltages are in phase. I have put the output of one honda into the other with an isolation transformer, inverting the signal and that gets you two generators out of phase. You can then tie the two neutrals and have 240V. I need to do a youtube on it. Have not seen it done and it does not require a very big transformer, meeting the generator specs, that is. Just has to provide syncing signal.

Honda inverter generators will ‘sync’ with an outside source if they are powered up with the source applied to their output. Not sanctioned by Honda, of course, but the circuitry seems to sync the generator since it is an inverter type. Much easier than syncing with a light bulb wired between them.

#4

Not that terrible, really. I’ve done it many times on a MEP-006A. The army helpfully provides the sync cable, too.

But the issue is that you have to constantly adjust the sync, particularly if there are big weather fluctuations. No automatic controls on those old bastards.

#5

But the issue is that you have to constantly adjust the sync, particularly if there are big weather fluctuations. No automatic controls on those old bastards.

Don’t they stay in sync once connected, barring some great change in frequency? Seems like they would want to stay ‘stuck’ together for the most part.

BTW, here are four EU2000i’s hooked together. I think the specs for the EU200i are that you can connect 3 of them together. Looks like the fourth one is not connected via the paralleling port. They must just have it tied into the other at the output. Start that one last and it will sync.

This brings up an interesting philosophy of how to set up generators. You could get a monster Honda inverter EU7000i for about the same price as four of the EU2000i.

4 x EU2000i easier to move but more to set up and you can just run what you need.

#6

You don’t need to add the transformer as it nets you no gain.

Leaving L1 and L2 separate (not tied together), pull half your 120 from L1 to N, the other half of your 120 from L2 to N. Make sure they remain separate 120 systems and there is no wierd coupling back from one to the other through your 120 circutiry (I have seen crazy wiring happen in older houses that many different repairmen operated through the years)

Your 240s are still available now, since you did not tie L1 and L2.

Based on the information from the problem statement, this solution should yield your best results, and allows you to hang on to your transformer for a different application. You would only suffer losses by putting it into play here.

#7

Thanks so much, James, for your response.
I agree. If you balance things to begin with then that’s the best you can do. I’m just thinking that you never really know what will be plugged in where or when in your house - microwaves, other high energy devices. Then, perhaps you could just put them on the same line together through the transformer.
But, as I noted, probably way too much work for a marginal improvement at those random times. Money and time and hardware probably better allocated to just get a bigger generator, I guess.
Cheers,
David Jackson

#8

L1 and L2 should be fused or 'breakered" so that if either gets overloaded, the unruly user of electricity gets the feedback from the system that they have committed an electrical crime…lol

Tying them together wastes power from your generator, and might even damage the thing. Whatever you figure out, I would for sure not tie L1 and L2 together, regardless of the fact that you have gotten away with it before. Large currents are unnecessarily created when you do this as they are 120 degrees out of phase with one another, according to my understanding.

Best of luck. Let me know if you have other ideas you would like to run by an electronics dude…

#9

Agree, tying L1 and L2 together is totally short circuiting the system if you are supplying 240 volts across them, as, yes they are 180 out of phase with a common neutral. If you don’t have any 240V devices or choose not to power them and only have 120V generator then you can definitely tie L1 and L2 together while keeping the main breaker off. Anything that draws 240V across L1 and L2 will see zero voltage and will be inactive unless, I suppose it has some additional wiring that draws from L1 or L2 and neutral.

#10

Datasheet and/or model number for generator would be most helpful here for me. And I would like to point out that power electronics was for sure never my specialization. I am a bit out of my element speaking to this subject, to be most truthful. I am a microelectronics/programmer/circuit board designer/small scale digital high speed signaling and simulation expert. Nowhere in that description is anything about delivering potentially lethal electrical currents. I took required EE coursework on power delivery and motors/generators as a senior in college. The coursework was challenging to me, and I was impressed with brushless induction motor designs…they have currents induced in these ferroius loops of metal attached to the motor’s drive shaft. These EM field induced currents in these conductors make the things work, which was always cool and fascinating to me.

During my career, I have always been able to leverage the expertise of semiconductor sales power delivery experts to get me solid supplies in systems I developed. This is the best anyhow as this is a purely analog science, and these guys spend their years keeping up with all the best design and analog power simulation techniques. No one person can do it all in this world. There is just too much information and time required to master the various arts. About the best one can hope for is to pick a good subject to grow into. Maybe 2 or even 3 for the suicidal. But at some point, you simply have to trust other experts in their area…something tough to do for some of us…

So when it comes to residential/commercial power delivery, its best to take my answers with a grain of salt. But I do know that three phase power has three conductors 120 degrees phase difference. I am not 100% certain about the outputs of your generator as I have yet to see the manufacturer’s documentation, but would like to…

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