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Can I plug both the 120V and 240V extension cords into my Champion 9000W generator?

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    Depends on the unit, of course. Please provide more information.
    – isherwood
    Commented Mar 15, 2021 at 14:59

2 Answers 2

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Yes and no. It's not as simple as keeping the wattage under the maximum value.

The load needs to also be balanced--if you have 120v devices the load needs to be on both legs equally or close. 220/240v loads are usually balanced, but not always. (A dryer is a example of an unbalanced 240 load).

On a 120v leg you can normally pull 2400w. Beyond this you will probably trip the protective circuits (for the single 120v outlets). Splitting the load and putting it evenly on each leg it will work so to not overload the generator.

You may be able put ~6000W on the 220/240 but then it depends how the 120v circuits are loaded. 1500w on each leg will work but a large imbalance will overload the generator even if the total is less than the generator rating.

I mention the loading because years back a man set up his own system. On the first power outage he kept tripping the generator over temp safeties (ruined the generator). They would not warranty it and called it abuse. I was referred to set up the new one. His problem 80/30--he had 30% on the 240 load then 50% on L1 leg nothing on L2 even though he had less than the total load it was so heavily imbalanced it smoked the coils from being reset.

I went out and he was really upset. He had done an excellent job setting it up but did not understand balancing and the inspector did not check it when he signed off the job.

I moved 3 circuits over to the other side and then asked him what he would add if he had power. I added 4 more circuits and his total was still well under the rating but well balanced.

I explained how to check the loads with the meter on the generator and to make sure L1 was close to L2 and he would be fine with 1-2 below the max but the large imbalance and resetting was what damaged the original generator.

He did not believe me and turned off his main and ran the generator for close to 250 gallons of propane without a problem.

So as the question is asked yes or no can be the correct answer depending on balancing of the 120v loads.

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  • What fascinates me with this particular size of generator is that if you (A) max out the 120V outlet assuming it has a 20A breaker and then also (B) fully max out the generator through a 240V outlet, the imbalance thus created IS LESS THAN the imbalance created if you just do (A) and stop. So a person who asks this question and does the worst possible job at implementing your good answer will be better off than a more naive person who just plugs a 2390W device into the 120V receptacle and goes happily on with life.
    – jay613
    Commented Mar 15, 2021 at 16:01
  • It makes me wonder if you could wire a transfer switch so instead of choosing between main and backup for each circuit, you instead choose which leg of the generator each load is on. Then you could easily switch the loads while watching the gauges until it's balanced. I'm not sure it would be worth doing, but it's an interesting idea.
    – mrog
    Commented Mar 15, 2021 at 16:26
  • @mrog yes there are transfer switches that allow individual circuits to be chosen these used to be the standard but are horribly expensive and all they really are is heavy duty double throw switches that you wire into your panel. In one position they are on the line feed in the other they are on the generator feed. Some do come with power meters also but an 8 circuit transfer no meter 375$ generac brand the first one I saw. Why pay this when a 60$ interlock kit lets you choose any circuit. I actually change loads if I want the mini split system to run for a while with the cheap interlock kit.
    – Ed Beal
    Commented Mar 15, 2021 at 16:48
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Yes you can provided that you don't exceed the wattage ratings. Smaller generators have a selector switch and you have to decide whether you want 120V or 240V but the larger ones let you run both voltages.

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