Portable Generator Electrical Question

Beltzington · Sep 13, 2018

My generator is rated at 30-amps and has a 120/240 L14-20 4-prong locking connector, reading the Owners manual and looking at the wiring schematic it is not clear to me how much amperage each 120v leg will provide. Is each leg rated to 20-amps, 10-amps or is the total combined limited at 20-amps? I understand I can't exceed the generators total amperage rating but want to know what each leg could supply individually. It also has several other outlets but I am just unclear on the 240V outlet. My guess is the breaker will kick if the total load on both legs exceeds 20-amps.

LittleBill21 · Sep 13, 2018

generally the 240v receptical has a separate circuit breaker, it would be rated at that, if it doesn't it will be whatever the highest rating is of the other 2 circuit breakers.

RNeumann · Sep 13, 2018

For a 240v 30a circuit each leg of the 240v is rated at 30a.

Is that what you are asking or are you asking about the 120v circuits?

Another option is to area photo of the spec sheet. We will get it from that.

Beltzington · Sep 13, 2018

Here is the wiring diagram -

Looking at 240 plug it looks like the two 120v legs (red and black) run thru two 20-amp breakers. Indicating a total plug ouput of 40-amps limited by the generator total output. Your thoughts?

RNeumann · Sep 13, 2018

Their’s not enough of the drawing to get a full picture. One plug looked like it had a 20a breaker and the other had a 30a breaker. I couldn’t see where the wires went off the bottom of the drawing.

Having 2 20a breakers feeding a 240v circuit makes a 20a 240v circuit. Not a 40a circuit. USA 240v is split phase- each phase has 20a on it. Adding the two phases increases the voltage- not the amps.

Beltzington · Sep 14, 2018

Thanks, I believe my questions have been answered. Each leg is protected by a 20-amp breaker, if total amp output of the generator was 40-amps I could provide a service panel with up to 20-amps at 240V or by splitting the 120V legs up 40-amps at 120V. Correct.

ruffdog · Sep 14, 2018

Here is an adapter that plugs into a 30a 4-prong that turns it into 2/ 15a 120v outlets.

https://www.walmart.com/ip/Camco-55438-PowerGrip-30M-2-x-15F-4-Prong-Generator-Adapter/54804134?wmlspartner=wlpa&selectedSellerId=0&adid=22222222227053103953&wmlspartner=wmtlabs&wl0=&wl1=g&wl2=c&wl3=152955437896&wl4=pla-264733218605&wl5=9059952&wl6=&wl7=&wl8=&wl9=pla&wl10=8175035&wl11=online&wl12=54804134&wl13=&veh=sem&gclid=CjwKCAjwuO3cBRAyEiwAzOxKshyeb35UCXKtgvVejBy3B0xozED2fglqkEIwRcJMGdyeWE9Ru3dv5xoC7rkQAvD_BwE

ruffdog · Sep 14, 2018

But then, this adaptor says it changes a 30a into two 20a outlets. ?????????

3-Foot 3-Amp 125/25-Volt Generator Y-Adapter - Champion Power Equipment

gary49 · Sep 14, 2018

You have 3 circuit breakers, according to the schematic. One 20 amp/120 volt single pole feeding a GFI receptacle which has a normal 120 volt receptacle downstream from it which is also ground fault protected, a 30 amp/120 volt single pole feeding a 30 amp/120 volt receptacle (generally used on shore power for a boat or to feed an RV) and a 20 amp/240 volt receptacle which you should use to plug in a cord to your emergency panel through a 20 amp 4 wire twist lock inlet adapter. Just make sure you have a breaker interlock or a double throw switch to make certain the generator power can't feed the panel at the same time as the normal power. I'm guessing your generator is rated for 4500 to 5000 watts, perhaps a 1000 watts more of surge power.

RNeumann · Sep 14, 2018

Beltzington said:
Thanks, I believe my questions have been answered. Each leg is protected by a 20-amp breaker, if total amp output of the generator was 40-amps I could provide a service panel with up to 20-amps at 240V or by splitting the 120V legs up 40-amps at 120V. Correct.

I think part of the confusion is how gens list their rating vs how a home is listed.

A home has say a 200a panel. That means each 120v leg has 200a for a total of 200a at 240v.

Sometimes the gen will say something like “40a gen”. Unfortunately that could be 40a at 120v. And if it will make 240v it’s only 20a.

So if you want to run multiple 120v items you will have 2 120v 20a circuits. Not one 120v 40a circuit.

The comment above about including the brand and model would help. Also, if you plan to backfeed a house panel their is more to the puzzle.

LittleBill21 · Sep 14, 2018

actually it appears he has a 120/240 switch, which with the crap drawing appears to give him 30 amp at 120 or 15 amp at 240, prolly flips the windings like my old 3k generator

Beltzington · Sep 14, 2018

RNeumann said:
I think part of the confusion is how gens list their rating vs how a home is listed.

A home has say a 200a panel. That means each 120v leg has 200a for a total of 200a at 240v.

Sometimes the gen will say something like ?0a gen? Unfortunately that could be 40a at 120v. And if it will make 240v it痴 only 20a.

So if you want to run multiple 120v items you will have 2 120v 20a circuits. Not one 120v 40a circuit.

The comment above about including the brand and model would help. Also, if you plan to backfeed a house panel their is more to the puzzle.

You may be surprised

but I actually have many years of electronic training and experience, however most of that was solid state, telecommunications and computer logic. As a result I am often confused by the terms and codes used in the residential electrical world, which is why I ask and why I appreciate your feedback. The wiring diagram is very small and hard to read but it does show the L14 plug 120V legs get power thru two 20-amp breakers. I don't need 240V during a power outage and don't want to have to move breakers around in the panel so I was looking at back feeding my panel via an outside 240v AC connect which I believe will provide 120V to all my breakers in my panel, clearly only a few of them could be on. I would turn off the main line breakers going into the panel and remove the line service disconnect to insure I do not hurt any Glen Campbell's of my county.

Generator is a JD gas powered JD G4400K

RNeumann · Sep 14, 2018

So yes, back-feeding, while not legal, can be done. It requires a systematic approach and is something the spouse or kids probably shouldn’t do without training. Hint- it starts with the main house breaker off and the gen off. I will mention manual transfer switches don’t cost an arm and leg anymore. We will still get flamed for discussing it here....haha.

Anyway, yes you can make a double male cord and back-feed the panel. For a small gen like that most would use the dryer plug or 240v in the garage. You will need to ensure the plugs and loads you take live on generator power are on separate phases. If you understand how the panel breakers are laid out that isn’t an issue-you may need to flop a few breakers.

ruffdog · Sep 14, 2018

RNeumann said:
So yes, back-feeding, while not legal, can be done. It requires a systematic approach and is something the spouse or kids probably shouldn稚 do without training. Hint- it starts with the main house breaker off and the gen off. I will mention manual transfer switches don稚 cost an arm and leg anymore. We will still get flamed for discussing it here....haha.

Anyway, yes you can make a double male cord and back-feed the panel. For a small gen like that most would use the dryer plug or 240v in the garage. You will need to ensure the plugs and loads you take live on generator power are on separate phases. If you understand how the panel breakers are laid out that isn稚 an issue-you may need to flop a few breakers.

So, is that why they suggest balancing the 120v loads when the gen is running (half the load on the left of the panel, half on the right)?

RNeumann · Sep 14, 2018

Yes- exactly. It’s hard to explain AC current without pictures and USA 240v is a little more complex. But basically it’s like hot and cold water coming out of the shower. Hot water is one leg and cold water is the other leg. In your panel all the 120v breakers are on either the hot or cold water and the 240v breakers use a hot AND cold. The panels stagger the breakers from side to side and vertically. So vertically it’s a hot,cold,hot,cold breaker etc.
When back-feeding the panel with a “small” gen that is only powering a few items you will want to ensure the loads are on the hot and cold equally. So say the frig is on the hot side and the tv, computer and a few lights is on the cold side. If everything was on one side it would overload the gen and trip the gen’s breaker. With some thought it can be done though.

***IN THE EXAMPLE ABOVE THE TERM HOT AND COLD TIES INTO MY WATER ANALGY ABOVE- NOT HOT AND COLD WITH REFERENCE TO ELECTRICAL CIRCUITS......clear as mud???!!! Haha

newbury · Sep 14, 2018

RNeumann said:
Yes- exactly. It痴 hard to explain AC current without pictures and USA 240v is a little more complex<snip>

Even with pictures and videos it's hard to explain.

How would you explain 3 phase with hot and cold water ?

BAP · Sep 14, 2018

Breaker interlock switches for switching to generator are fairly cheap now and a safe way to isolate the panel from the grid.
https://www.homedepot.com/p/Square-...}++dln:{541708}+qu:{breaker+interlock+switch}