# Single Phase 240V Generator watts per line?



## Danny LA (Oct 30, 2021)

On a 12,500 running watt generator when using it at 240 volts are the max running watts divided between the two hot lines (6250 max running watts on line 1 and 6250 max running watts on line 2)? Or can I put 12,500 watts on ether one of the lines at 120 volt? I would like to see documents explaining this.


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## OrlyP (Oct 19, 2021)

My 2c.

240V @ 12,500W means it will be drawing about 50A (P=VI), with a pf=1. To get 240V, the two 120V windings are connected in series (tied Neutral). When in series, you’re adding up the voltage but the current capacity remains the same. So each 120V winding can do 50A independently, which translates to about 6,000W.

All this to say that you are correct. Each 120V leg can theoretically handle half the generator’s capacity. However, you are limited by the current capability of the receptacles. For example, you can’t pull 50A from a 20A receptacle, obviously.


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## exmar (Jun 29, 2015)

Agree, also, when it comes to the 120V receptacles most generators have breakers to assure you don't exceed their rating. Typically, to use the entire output of the generator, in your case, 12,500W, would be to use the 240V connection.


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## Danny LA (Oct 30, 2021)

OrlyP said:


> My 2c.
> 
> 240V @ 12,500W means it will be drawing about 50A (P=VI), with a pf=1. To get 240V, the two 120V windings are connected in series (tied Neutral). When in series, you’re adding up the voltage but the current capacity remains the same. So each 120V winding can do 50A independently, which translates to about 6,000W.
> 
> All this to say that you are correct. Each 120V leg can theoretically handle half the generator’s capacity. However, you are limited by the current capability of the receptacles. For example, you can’t pull 50A from a 20A receptacle, obviously.


*Thanks, I just never knew the answer for certain. "Each 120v leg can theoretically handle half the generators capacity"*
I don't have a problem, my house 120v loads are pretty balanced between the two lines. I understand the generator receptacles may be limited, but when connected to a house panel using 240v the house panel can put higher 120v loads on one line than the other.


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## iowagold (Jan 22, 2020)

i get lucky...
i do not need 240 now so i can run in the 120 mode when on gen set.

yes when in the 240 mode you need to be balanced on your load to operate right.
pm if you need links for a meter setup for your breaker panel.
it is nice to see live what the exact power load is at any time.


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## Moneypit6 (Nov 1, 2021)

So if hooking up to an inverter generator, typically you only get a 30 amp 240v plug. That's only 3600 watts. But the larger inverter generators like the Champion are 7000 watts running. How do you hook that up with a plug to the house when only a single 30 amp 240v plug being available on the generator??


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## Danny LA (Oct 30, 2021)

Moneypit6 said:


> So if hooking up to an inverter generator, typically you only get a 30 amp 240v plug. That's only 3600 watts. But the larger inverter generators like the Champion are 7000 watts running. How do you hook that up with a plug to the house when only a single 30 amp 240v plug being available on the generator??


The 240 volt plug has two hot lines (or poles). Each one to neutral would be 120 volt. Watts divided by volts gives you amps. 7000 divided by 240 is 29.16. You would have up to 29.16 amps per line (or pole). 58.32 amps max counting both of them.


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## Danny LA (Oct 30, 2021)

Danny LA said:


> The 240 volt plug has two hot lines (or poles). Each one to neutral would be 120 volt. Watts divided by volts gives you amps. 7000 divided by 240 is 29.16. You would have up to 29.16 amps per line (or pole). 58.32 amps max counting both of them.


The amp rating of the plug doesn't mean the generator can put out that many amps. The plug rating should be at or greater than the generator out put. The generator rating is important. It would be fine to have a 50amp plug on a generator that can only put out 20 or 30 amps.


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## Moneypit6 (Nov 1, 2021)

So a 240v 30 amp plug means 30 amps per leg. Okay, so any generator over 7000 watts that doesn't have a 50 amp 240v plug would be a waste due to the draw on the plug tripping the internal breaker. I've seen 10,000 watt generators with only a 30 amp 240 plug. I couldn't figure out why someone would buy that when only 7200 watts are usable if connecting the 30 amp 240v plug to their house. Sounds like a Champion 100520 7000 running watt generator is the sweet spot for anything without a larger than 30 amp 240 outlet.


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## drmerdp (Apr 10, 2018)

Moneypit6 said:


> So a 240v 30 amp plug means 30 amps per leg. Okay, so any generator over 7000 watts that doesn't have a 50 amp 240v plug would be a waste due to the draw on the plug tripping the internal breaker. I've seen 10,000 watt generators with only a 30 amp 240 plug. I couldn't figure out why someone would buy that when only 7200 watts are usable if connecting the 30 amp 240v plug to their house. Sounds like a Champion 100520 7000 running watt generator is the sweet spot for anything without a larger than 30 amp 240 outlet.


Keep in mind, lots generators are advertised at 7000+Watts but… it’s actually rated for less then that. The larger number is the surge wattage. Pretty much a number devised to confuse the consumer.

Also, it’s best to run any generator at below its rating.


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## OrlyP (Oct 19, 2021)

I heard a few generator techies say to run no more than 80% of the continuous/running Watts of your generator. That way, you'll still have headroom for loads that have a lower than ideal power factor. Especially true if you don't have an indicator for pf when running your loads.


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## Danny LA (Oct 30, 2021)

Moneypit6 said:


> So a 240v 30 amp plug means 30 amps per leg. Okay, so any generator over 7000 watts that doesn't have a 50 amp 240v plug would be a waste due to the draw on the plug tripping the internal breaker. I've seen 10,000 watt generators with only a 30 amp 240 plug. I couldn't figure out why someone would buy that when only 7200 watts are usable if connecting the 30 amp 240v plug to their house. Sounds like a Champion 100520 7000 running watt generator is the sweet spot for anything without a larger than 30 amp 240 outlet.


You receptacle *should always be rated to handle the running watts.* The surge watts from motors, compressors and etc. are from LRA (locked rotor amps) this is only for a fraction if a second to get the motor turning from being stopped.


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## iowagold (Jan 22, 2020)

that is why we modify the eu7000is for the 50 amp twist locks.
heavy duty and you can get the better connection.
pm if you need links for the better 50 amp twist lock mod.


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## Danny LA (Oct 30, 2021)

iowagold said:


> that is why we modify the eu7000is for the 50 amp twist locks.
> heavy duty and you can get the better connection.
> pm if you need links for the better 50 amp twist lock mod.


A good quality receptacle and male plug at any amp rating will make a good connection, the twist lock just latches the plug from being pulled straight out.


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## LaSwamp (Mar 16, 2021)

OrlyP said:


> I heard a few generator techies say to run no more than 80% of the continuous/running Watts of your generator. That way, you'll still have headroom for loads that have a lower than ideal power factor. Especially true if you don't have an indicator for pf when running your loads.


Ideally, the most efficient max load on a generator is 50% of its total running capacity. Once you pass that, fuel use increases. At 80%, you're running the generator pretty hard and using a lot of fuel. That can become an issue if fuel is hard to come by during an extended outage.


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## iowagold (Jan 22, 2020)

yup lower demand is a better run.


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## Danny LA (Oct 30, 2021)

It sounds like my thinking was correct when connecting at 240 volt (120v to neutral)








.


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## OrlyP (Oct 19, 2021)

LaSwamp said:


> Ideally, the most efficient max load on a generator is 50% of its total running capacity. Once you pass that, fuel use increases. At 80%, you're running the generator pretty hard and using a lot of fuel. That can become an issue if fuel is hard to come by during an extended outage.


As far as the 80% goes, I'm told that it's just a recommended maximum you should run your generator continuously at, only IF you have to. It's not to say that you should.

In my use case, load testing with everything I need turned on during an outage, I'm at around 75-80%. But that's sort of the worst case scenario. In real world usage and once the inverter A/C has settled, power requirements drops down to around the 40-60% range of the generator.


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## iowagold (Jan 22, 2020)

if you can keep under 50% that is a good number.
that leaves you with headroom.

things start to happen on waveform above 50% in the lab.

back to distortion and thd that can happen from a bad motor or bad slots on a motor.
lights that have a noise issue.
so if we stay lower on the total demand from a gen set..
things do not get out of hand.


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## Danny LA (Oct 30, 2021)

My 12,500 watt generator ran 24/7 for 9 days after Ida. I just shut it down every 4 days to change the oil. In South Louisiana air conditioning is my highest load. My 12,500 max running watts per line is 6250 watts. When my 3.5 ton AC is running the highest amps I ever noticed on a line was 22 amps or 2640 watts. If both were 2640 x 2 = 5280 total watts. Which is just 42.24% load. For Ida I used 29.95 CCF of natural gas a day which cost $28.45 per day. This was so much better than having to buy gasoline!!! 
In 2009 and 2021 I ran some test on some electric appliances. My refrigerator compressor uses 228 watts, surge up to 1424 watts, defrost 552 watts and the compressor/defrost run time was 61.8%. My freezer compressor uses 144 watts, surge up to 1225 watts, defrost 420 watts and the compressor/defrost run time was 77.2%. The high percent of run time surprised me. I also test some window units: 5000 BTU used 444 watts and a 8000 BTU used 744 watts.


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## drmerdp (Apr 10, 2018)

Danny LA said:


> My 12,500 watt generator ran 24/7 for 9 days after Ida. I just shut it down every 4 days to change the oil. In South Louisiana air conditioning is my highest load. My 12,500 max running watts per line is 6250 watts. When my 3.5 ton AC is running the highest amps I ever noticed on a line was 22 amps or 2640 watts. If both were 2640 x 2 = 5280 total watts. Which is just 42.24% load. For Ida I used 29.95 CCF of natural gas a day which cost $28.45 per day. This was so much better than having to buy gasoline!!!
> In 2009 and 2021 I ran some test on some electric appliances. My refrigerator compressor uses 228 watts, surge up to 1424 watts, defrost 552 watts and the compressor/defrost run time was 61.8%. My freezer compressor uses 144 watts, surge up to 1225 watts, defrost 420 watts and the compressor/defrost run time was 77.2%. The high percent of run time surprised me. I also test some window units: 5000 BTU used 444 watts and a 8000 BTU used 744 watts.


That’s a very detailed breakdown, you definitely did your homework. $28 a day to run that big generator is great. It would have been atleast double, probably triple that cost for gasonline. Plus, the burden of finding gas along with Everyone else.


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## iowagold (Jan 22, 2020)

yup NG is way lower cost to run per hour.
and you do not have to worry about storing it!


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