Autoformers for low pedestal voltage

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kdarling
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Autoformers for low pedestal voltage

Post by kdarling »

So, after getting a scare with my roof AC not wanting to start, I've done some Googling. (Btw, with the hard start kit, the compressor now starts instantly with no straining sound whatsoever.)

Watching the new AC volt and amp meters that I installed a few weeks ago, I noticed that the power from my garage hookup was dropping to the minimum necessary to keep compressors happy. Sometimes it drops as low as 108 volts, which is right on the edge of real problems.

While reading about how low voltage causes motors to pull more amps and heat up and fail, I ran across lots of references to RV autoformers, which are multi-tap transformers electronically switched to boost pedestal voltage by anywhere from 8 to 16% depending on make and model. Basically at 10% boost, my 108 volts would jump to 119 volts, thus safe guarding my AC and microwave.

A major supplier is Hughes, with both 30 amp and 50 amp models. See their explanatory video at the bottom of this page:

https://hughesautoformers.com/

Has anybody here any experience with an autoformer? Has anyone installed one permanently in their RV with a kit?

Thanks in advance! I'm really leaning towards getting one to help prevent expensive appliance damage.
1994 Concourse dinette, Ford 7.5L (460 V8)
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kdarling
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Re: Autoformers for low pedestal voltage

Post by kdarling »

Well, the other hot day I watched my garage fed shore power drop to like 103v, causing the AC to pull 14+ amps, and that was enough for me.

I found a used Hughes 30A model on eBay for about $200, and hooked it up outside for now. (My eventual plan is to put it in the side shore power cord bay, since it's only about 5x5x12")
Hughes Autoformer
Hughes Autoformer
image.jpeg (16.14 KiB) Viewed 1024 times
What a difference! Now when the AC compressor kicks in, I can see the outside power dip from 120v to 105v for just an instant, before the Autoformer kicks in and boosts it back up to 113-115v, well above the danger level of 105v. And at that voltage, the compressor only draws about 11-12 amps.

So... if you use pedestal power at RV campgrounds.(or a 20A home source like me), it might save a lot of future grief to use one of these devices to keep the voltage up.
1994 Concourse dinette, Ford 7.5L (460 V8)
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Blue~Go
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Re: Autoformers for low pedestal voltage

Post by Blue~Go »

Interesting you post this just now. I was just talking with a friend who is going to be upgrading the electrical in his new RV. He's the type to have a 2000 watt "whole house" inverter charger, and we were looking over the Victron models that have power sharing. I haven't completely read up on it yet, but the idea is that say you pull up to a friend's house and plug into their 15 amp outlet. Then you want to run your air conditioner. The inverter makes up the power from your battery bank (say your AC pulls 17 amps). That way you go on as if nothing happened, and your batteries of course lose some amp hours but not that much.

What I'm wondering is would that still help in a low-voltage situation. For example right now he's at an RV park that, when everyone else there plugs in their coffee makers and etc. in the morning, can go down to 105 volts. Would the power sharing kick in in that situation? I aim to find out. I don't use power in that way, but I like to know what's out there and how things work.

Not saying it's in the same league as what you just got (I'm sure there is a hefty price difference!), but just that not an hour ago I was thinking about this as I was driving along (in a car).
1999 Concourse
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