Hughes Autoformer and Incoming Amperage question

[gbkims]

I just got a Hughes Autoformer so was interested in this.
1st I looked at the Autoformer for its Nameplate Rating as you see on most equipment. No Nameplate info.

So rough estimate for a 30A Autoformer disregarding its Effeciency, the Reactive Power being used by Motors on the load side, the Power Factor.
Because all we care about is do we trip the 30A breaker feeding the RV.
Power In & Out of the Autoformer would be about equal (minus losses in the Autoformer)

Autoformer: Input of 108V, output of 118V.
Output 118V x 30A = 3540 Watts of Power being used. ExI = P
Input 108V x 32.78A = 3540 Watts of Power being delivered. 3540/108 = 32.78A Input of the Autoformer.

So if 29.5A input to the Autoformer at 108V = ~ 27A at 118V on Output of Autoformer.

Note: I'm not a EE or was ever a licensed electrician.

[el Rojo]

The way I understand it the answer would be "maybe" At 108 the AC may be less efficient so it draws 13 amps to run, at 116 maybe it only needs 11 and the autoformer is using 2 amps to boost the voltage(completely made up numbers) so in the end the current draw may be similar.

What I'm really wanting to know is if the one RV park we went to in OR who refused to let people use the "boosters" because they used more amperage than without the "booster/Autoformer" was correct in their thinking.

[JKellerJr]

What I'm really wanting to know is if the one RV park we went to in OR who refused to let people use the "boosters" because they used more amperage than without the "booster/Autoformer" was correct in their thinking.

Yes that is the crux of the issue. Potentially yes, you will be using extra amps, I don't think higher voltage means everything in the trailer will be more efficient thereby "breaking even". My answer to that is even if you are using more amperage you still cant use more than the breaker will allow. So on a 30 amp service you cant go over the 30 without tripping the breaker anyway. If i'm paying for a 30 amp service then we should be able use 30amps (or 50 etc). The real reason they don't want you to use it is they hoping no one is using there full allotment as their system is not able to give it to you. So if everyone was using one, their system would be exposed to being inferior. Its easier to blame the autoformer then to admit they cant supply you with what your paying for.

[jkwilson]

What I'm really wanting to know is if the one RV park we went to in OR who refused to let people use the "boosters" because they used more amperage than without the "booster/Autoformer" was correct in their thinking.

Not an easy answer. If you use an autoformer, you are using power when others have to shut things down. In a way, you are still eating your full piece of pie when others can’t. You aren’t eating their pie, you are eating yours. But they can’t have their whole piece because there isn’t enough to go around.

Use an extension cord and put your autoformer under a tarp or in a tote. We have parked our bikes around it and draped a tarp over them.

[JKellerJr]

In a way, you are still eating your full piece of pie when others can’t. You aren’t eating their pie, you are eating yours. But they can’t have their whole piece because there isn’t enough to go around.

Very good analogy.

Edit:

But everyone is still paying for a whole pie.

If you cant supply 30 amps or 50 amps that eliminate them and cut everyone to 20. Now they wont do that cause they'll lose business

[DougW9876]

I wish a real electrical engineer would weigh in on this thread. Lacking that, my theory is:

The air conditioning motor needs a certain amount of electrical current (watts) to run. It is also designed to run most efficiently at 120VAC. Running it at a lower voltage will require more amps to get the job done. Using an autoformer should allow the AC to run at it’s most efficient so the overall power usage should be the same.

[jkwilson]

I wish a real electrical engineer would weigh in on this thread. Lacking that, my theory is:

The air conditioning motor needs a certain amount of electrical current (watts) to run. It is also designed to run most efficiently at 120VAC. Running it at a lower voltage will require more amps to get the job done. Using an autoformer should allow the AC to run at it’s most efficient so the overall power usage should be the same.

This is correct. But assumes AC is the only load. If everyone switched their refrigerators and water heaters to propane, it would be much better. I am an electrical engineer.

[el Rojo]

Yes that is the crux of the issue. Potentially yes, you will be using extra amps, I don't think higher voltage means everything in the trailer will be more efficient thereby "breaking even". My answer to that is even if you are using more amperage you still cant use more than the breaker will allow. So on a 30 amp service you cant go over the 30 without tripping the breaker anyway. If i'm paying for a 30 amp service then we should be able use 30amps (or 50 etc). The real reason they don't want you to use it is they hoping no one is using there full allotment as their system is not able to give it to you. So if everyone was using one, their system would be exposed to being inferior. Its easier to blame the autoformer then to admit they cant supply you with what your paying for.

And there you have it!!!! You hit the nail on the head. Now you have dumbed it down enough for me to understand. LOL.

Red

[el Rojo]

Not an easy answer. If you use an autoformer, you are using power when others have to shut things down. In a way, you are still eating your full piece of pie when others can’t. You aren’t eating their pie, you are eating yours. But they can’t have their whole piece because there isn’t enough to go around.

Use an extension cord and put your autoformer under a tarp or in a tote. We have parked our bikes around it and draped a tarp over them.

Thank you. Another good answer.

[Canyonlight]

Great discussion, all ! I am far from having even modest electrical knowledge but the feedback on this thread has been very helpful.....good stuff !

Dan