Generator and Shore power, someone school me please

**Empyrials** · 05-30-2019, 07:47 PM

Ok so here's what i've come to believe will work, and i want to know if i'm wrong. So the little i know of electrical code it's wrong, but the AC is on a 20AMP circuit so it shouldn't matter, and judging by how others have done it, i believe it's safe and just wanted a 2nd opinion.

I attached an image that would show how i could cut out the main 15k A/C if i have a generator or 2nd power source plugged into the 30amp outlet. I'm using a progessive Automatic switch that would default to Shore power but if it senses a 2nd power source it will swap to it. If the 2nd power source stops it will switch back to shore power. Do i need to introduce a small fuse box that has a 20AMP Breaker that goes from the 30AMP plug and the Progressive ATS? The Genny has a fuse breaker in it so that's why i was thinking i didn't need a fuse box but let me know your thoughts.

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**gbkims** · 05-30-2019, 09:53 PM

Originally Posted by Empyrials

Ok so here's what i've come to believe will work, and i want to know if i'm wrong. So the little i know of electrical code it's wrong, but the AC is on a 20AMP circuit so it shouldn't matter, and judging by how others have done it, i believe it's safe and just wanted a 2nd opinion.

I attached an image that would show how i could cut out the main 15k A/C if i have a generator or 2nd power source plugged into the 30amp outlet. I'm using a progessive Automatic switch that would default to Shore power but if it senses a 2nd power source it will swap to it. If the 2nd power source stops it will switch back to shore power. Do i need to introduce a small fuse box that has a 20AMP Breaker that goes from the 30AMP plug and the Progressive ATS? The Genny has a fuse breaker in it so that's why i was thinking i didn't need a fuse box but let me know your thoughts.

If you're plugging into the generator's 30A outlet, then the A/C wouldn't have 20A overload protection.
I'd want a 20A CB inline to the ATS from the generator.

**Empyrials** · 06-11-2019, 08:53 PM

ya, you're right. I'll plug into the generators 20amp and change the 30amp plug to a 20amp. that way it's fused 20 amp by the generator. If i put a 20amp GFCI outlet will the AC trip it with the high surge when the compressor kicks on?

**el Rojo** · 06-12-2019, 07:59 AM

This is an interesting thread and I'm not trying to be a smart alec but we just use 1 AC and a electric fan.

Red

**gbkims** · 06-12-2019, 08:39 AM

Originally Posted by Empyrials

ya, you're right. I'll plug into the generators 20amp and change the 30amp plug to a 20amp. that way it's fused 20 amp by the generator. If i put a 20amp GFCI outlet will the AC trip it with the high surge when the compressor kicks on?

Wouldn't see why the Generator's 20A CB would trip as long as it's just powering the one A/C. The A/C is normally feed by a 20A CB from the trailer panel.
GFCI outlets are just supposed to trip on when equipment fails and there's .005A/5mA hot to ground current leakage detected, like if we touched the equipment when wet.
That's to protect us from heart fibrillation caused by the current running thru us to get to ground.

**Empyrials** · 06-12-2019, 10:22 AM

Originally Posted by el Rojo

This is an interesting thread and I'm not trying to be a smart alec but we just use 1 AC and a electric fan.

later on In triple digits i really want the 2nd AC, which is why i was was going down this path. I don't have the generator yet, but this already helped out the other weekend when we were at the lake. The 50Amp plug was taken, but i had a 30Amp and 20Amp available for me, so i plugged in the 30amp to the RV(to power 1 ac and everything else) and ran my 20amp cord over to my plug i made to power the main AC. Main AC on the 20amp fuse and the rest of the rig on the 30amp, worked well with 8 people in the rig.

Originally Posted by gbkims

Wouldn't see why the Generator's 20A CB would trip as long as it's just powering the one A/C. The A/C is normally feed by a 20A CB from the trailer panel.
GFCI outlets are just supposed to trip on when equipment fails and there's .005A/5mA hot to ground current leakage detected, like if we touched the equipment when wet.
That's to protect us from heart fibrillation caused by the current running thru us to get to ground.

yes i'll just use it to power the main AC. i'll just swap out the 30amp for a 20amp gfci and call it a day. Everything will be good at that point, awesome

**el Rojo** · 06-12-2019, 01:20 PM

Another tactic that can be applied, is using a Hughes Autoformer. It comes in handy in low voltage situations that commonly appear in older 30 amp Corp parks. Run you fridge and water heater on propane and then you can usually run 2 AC's off the 30 amp service. You will need to monitor your voltage and not let it drop below 108 volts or damage can occur. You also have to remember to turn off 1 AC before you use the microwave.

Empyrails I know this is not exactly what you were asking in this thread but it gives another "work around" to achieve the same results. The Hughes Autoformer isn't cheap though, I think I paid $550 or so for mine around 2002.

Red