# basic electricity question



## Mike Geldert (Oct 3, 2017)

This is not a real scenario, I'm not planning on hooking anything up. 
So let's say I have three generators. The first can output 7500 watts (open frame, loud) and the second/third can output 3000 watts each(inverter type). 
I have a 30amp power inlet (https://www.amazon.com/Reliance-Controls-Corporation-PB30-Generators/dp/B000BQT47S/ref=sr_1_fkmr3_1?ie=UTF8&qid=1507056051&sr=8-1-fkmr3&keywords=14-50R+power+inlet+box







When i run my large Generator I can input 7500 watts. (this is using a 240v connection). Now, if I had no 240v items I needed to run, and if I wanted to output from my two 3000 watt generators (total of 6000 watts in parallel) I couldn't use the 30amp inlet because the two inverter generators can only output at 120v. (6000 watts at 120v would exceed the 30amp rating). we can forget about what other challenges i'd have inputting 120v to my panel via the 30amp plug, I'm really just curious why the plug can't handle the lesser wattage at 120v.


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## thehandyman1957 (Feb 11, 2017)

The reason you can't use 6000 watts through the 30 amp plug is because it would all be going through one leg on the plug thus overloading it. 

Your larger Generator splits up the wattage between two legs on the 30 amp 220 plug and thus being able to 

split the wattage on to two legs of the plug keeps it from over loading.

On your inverter type generators, can they be synced so that you could use one generator per leg, 

thus creating the same conditions being given by your larger generator?


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## exmar (Jun 29, 2015)

Great question, though I'm getting a headache thinking about it. The only way I could see it working would be "IF" you could sync the two inverters in parallel and feed a 120/240 transformer to feed the load center. No, in addition to the very expensive cost for the transformer, starting up and taking off line would be very interesting to say the least. I'm remembering bringing a generating station online and connecting to the grid, get as close as we could then close in the switchgear and the grid would take care of the rest. This scenario is kind of the exact opposite.


As to the original question, assuming no 240V loads, a neutral would have to be added for each genset or a larger one capable of handling 50Amps. Obviously either would preclude the use of the 30A power inlet. Just connecting directly would result in an overloaded neutral which is somewhere we don't want to be. 


Perhaps the simple answer is that 120VAC is not 240VAC. When connected in a 120/240VAC configuration, the neutral current flow is the difference, not the total. " The current flow in the Neutral deserves a special look. Since the currents ‘flow’ in opposite directions we subtract to get the net current flowing in the Neutral. If Load 1 and Load 2 are exactly the same size the Neutral current will be Zero" Here's the rest of the article: 

https://www.bluesea.com/resources/86


I think I'd be selling the two inverter gensets and getting a traditional 120/240 unit.


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## Mike Geldert (Oct 3, 2017)

exmar said:


> Great question, though I'm getting a headache thinking about it. The only way I could see it working would be "IF" you could sync the two inverters in parallel and feed a 120/240 transformer to feed the load center. No, in addition to the very expensive cost for the transformer, starting up and taking off line would be very interesting to say the least. I'm remembering bringing a generating station online and connecting to the grid, get as close as we could then close in the switchgear and the grid would take care of the rest. This scenario is kind of the exact opposite.
> 
> 
> As to the original question, assuming no 240V loads, a neutral would have to be added for each genset or a larger one capable of handling 50Amps. Obviously either would preclude the use of the 30A power inlet. Just connecting directly would result in an overloaded neutral which is somewhere we don't want to be.
> ...




Thanks for the response! 
Seems like the neutral would surely be an issue. That is now clear. if the hots from the parallel gens are jumpered across the two hots in the 14-30 cable, I'm not clear if those too would be too much for the two wires, but the neutral makes it clear why it can't be done (at minimum the neutral is a problem). 

I don't have the described generators, but I was thinking about how these may be hooked up and the 120 vs 240 caused me to inquire. I appreciate the responses!


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## exmar (Jun 29, 2015)

The "Hots" would have no problem with 3000W as that would only be 25Amps and the plug and wiring is rated for 30A. It's when you combine the neutral you end up with 50A and like I said, we don't want to go there.


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## Desy 20 (Oct 12, 2017)

You made a very interesting observation. Why do you think so?


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