JoeChiOhki
Keizer, Oregon
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I've heard this term used a few times, but exactly is an autoformer? From what I've gleamed, it regulates the voltage, but is that all it does? Does anyone make a 20 amp version?
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summutt2002
Mountains of Utah-7000'
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Here you go.
Great wife, 3.1 dogs and no money..LIFE IS GOOD
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hershey
Albuquerque,(fulltime) NM, USA
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Boy O Boy did you open a can of worms..........
Those of us who own an autoformer think they are great and do a fantastic job. Those who don't will certainly chime in as to the "fact?" that they rob other campers of available power. But here goes my experience.
An autoformer will and does only kick in when the available voltage either 30 amp or 50 amp, falls to below a safe level. Then it boosts the voltage to an acceptable level, or tries to. I've only been in one brownout that the autoformer couldn't provide adequate voltage and my surge protector turned everything off until things leveled off.
The two most popular brands of autoformer is Hughes and Franks. Both have plusses and minues over the other. I use the Hughes and I'm well pleased with it.
As to a 20 amp model? I don't think that thats available, but.....you can certainly use the 30 amp model on a 15 or 20 amp shorepower. Mine is plugged into a 20 amp circuit right now. Having said that, the 30 amp model won't increase the amperage of that 20 amp circuit, only maintain the available voltage to a useable amount.
Now I'll step back and listen to how its illegal and downright un-christian to use one. 
hershey - albuquerque, nm
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bill13924
California
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I have never seen aversion less than 30amps... Since the amps can vary from park to park (the quality of their service) the Autoformer will boost the power uo to about 10%. I have been saved several times and considering the consequences (tv, computer, ect.) I have paid for it...
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JoeChiOhki
Keizer, Oregon
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Mk, just wondered if they did anything else besides maintain voltage, like clean the current sine wave, etc....
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wa8yxm
Wherever I happen to park
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No, an autoformer is short for "Automatic Transformer" Many (if not all of them) also contain MOV's to clip spikes, but all they do is maintain proper voltage.
They do work.. I'm still doing some testing.. I need MONEY to install several volt meters in my rig.
Nothin adds excitment like something that is none of your business
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tvman44
Southwest Louisiana
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Never could see how a Autoformer could rob other people of power. If you boost the low voltage your A/C and any other electric motor will draw less current than what it would draw with low voltage. Just an old wives tale started by people that know nothing and spread by people that don't know any better either.
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Hurricaner
Hurricane Utah
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tvman44 wrote:Never could see how a Autoformer could rob other people of power. If you boost the low voltage your A/C and any other electric motor will draw less current than what it would draw with low voltage. Just an old wives tale started by people that know nothing and spread by people that don't know any better either. Although motors will usually draw lower amperage, anything with a heating element such as an RV reefer will draw more current as the voltage rises. Not an old wise tale...just ohms law.
Sam
Sam & Kari
Hurricane, Utah
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Chuck&Gail
In the Colorado Mountains
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We found we need ours in about 20% of the CGs we visit. Works fine. Ours is a Hughes.
Note you can use a 30 amp version on a 20 amp line just fine, as 30 is more than 20. You could not use a 20 amp version on a line drawing 30 amps, if you could find one, as you would let all the smoke out and it would quit working.
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Bushey562
Norco, CA
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tvman44 wrote:Never could see how a Autoformer could rob other people of power. If you boost the low voltage your A/C and any other electric motor will draw less current than what it would draw with low voltage. Just an old wives tale started by people that know nothing and spread by people that don't know any better either.
"Stealing" may not be the right word. But the use of an autotransformer when the campground voltage is low will indeed result in you getting more power at the expense of your neighbors, whose voltage will drop even lower when you turn on your autotransformer.
Consider the following very simplified scenario:
You and one neighbor in a remote part of the RV park share a long power feed from the park's distant main feed. I'll assume that the main feed is always at 120vac, but that the long power wires shared by these two remote sites have a resistance of 0.25 ohms (not unlikely - that's only 200 feet of #8 cable).
Further assume that both of you are using exactly the same appliances which would add up to each of you drawing 25 amps if the voltage remained at 120 volts.
But the voltage won't remain at 120 volts (because of the resistance in the long power feed). Under these conditions, the voltage at each site will be 108.68 volts and each site will be drawing 22.64 amps.
Now, suppose you, but not your neighbor, installs an autotransformer. The Hughes Autoformer product increases voltage by a fixed 10% in a low-voltage situation, so that inside your RV, you now have 118.38v. This raises your current draw inside the RV up to 24.66 amps. (This additional load causes more voltage drop in the shared line, dropping the voltage coming into each RV to 107.62 v. so your inside voltage increased a bit less than the expected 10%).
Your use of the autoformer has reduced your neighbor's voltage from 108.68 v. to 107.62 volts, reduced his current from 22.64 amps to 22.42 amps, and reduced his power usage from 2.46 kilowatts to 2.41 kilowatts. Your voltage inside the RV increased from 108.68 to 118.38, your inside current increased from 22.64 amps to 24.66 amps, and your power from 2.46 kw to 2.92 kw. Your neighbor has a 2% power reduction while you see a 19% increase in your own power usage. This analysis assumes that the loads in your RV are resistive - see footnote.
This seems like a pretty good tradeoff, unless your neighbor has a power management system that shuts off her power when the voltage drops below a certain level. In some situations, your ability to use additional power by using the autotransformer could result in enough additional incoming voltage reduction so that your neighbor loses power completely. If you want to be a nice guy, you can turn off a bit more of your own power usage, returning his voltage and power to where it was before you used your autotransformer while still retaining the advantage of having normal voltage in your own rig.
Note that even though you may have a 30-amp power pedestal, you can not increase your internal current all the way up to 30 amps in a low-voltage situation. This is because when the autotransformer increases the inside voltage by 10%, (which is a 20% increase in power), it also must increase the current drawn from the power pedestal by a bit over 20%. So if you turned on 30 amps of loads inside the RV, you would be drawing considerably more than 30 amps from the pedestal, tripping the 30 amp circuit breaker.
Also note that if you and your neighbor both have autotransformers, you both win, since you both have higher voltage and more available power inside your rig. The campground owner loses a bit - a few hundred watts of additional power loss in the campground wiring.
We won't argue about whether the campground wiring in the above example meets code or not - a major reason for buying an autotransformer is that many rural campgrounds have wiring that is not designed to modern codes.
The ethics of increasing your own share of an inadequate power supply at the expense of your neighbors are debatable. Some might say it's unethical to run the heater (or the air conditioner) at all, in situations where there is inadequate power to supply everyone. Others will say "hey - the campground owners are at fault, I paid for 30 amps, and I'm simply using what I paid for".
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