Hughes Autoformer and Incoming Amperage question

[TheGuy]

While trying to find an answer to my question about what happens to the incoming amperage, I ran across this statement made by David Zomorrodian, one of the owners of Hughes Autoformers: "The autoformer changes amps into volts and draws fewer amps from the park and converts those amps into more volts inside the RV."

Now, somehow to my thinking and limited knowledge of electrical theory, this seems to be some snake oil marketing and bordering on the absurd! Would anyone who knows electrical theory care to jump in here?

Electricity is as we usually talk about is a combination of volts and amps called watts. Watt's law says wattage=volts*amps. So, extrapolating a bit from that you can indeed trade voltage for amperage and vice versa. For instance 8A*1V = 1A*8V = 2A*4V... You still end up with 8 watts.

The common analogy in DC electrical is volts are pressure and amps are flow. If you think of a water pipe... With a big pipe you can flow a lot of water but struggle to build pressure. If you have a smaller pipe, pressure builds more easily, but to get that same amount of water through you'd have to have more pressure to push the water through faster. It's not quite that simple in AC electrical, but the relationship is largely the same.


What the autoformer is doing is drawing more amps from the source to "pump" the amps to your rig harder, increasing the "pressure"/voltage. It's common in low voltage DC electronics to do this when you want to power a device needing say 5V but you want to use a couple AA batteries (1.5v*2) to keep it small.


As others have said, if you have 113V with no load on that circuit (including other outlets, etc) then a call to the power company is probably in order.

Hope that's not too confusing.

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[Mr. Goodwrench]

Thank you for the explanation of how an autoformer works. In my original post I tried to explain that my wire run from the sub panel to the pedestal is very long, over 80 feet so I am experiencing quite a bit of line loss. Will the amperage increase in the run from the panel to the pedestal when using the autoformer?

[TheGuy]

Just asked my b-i-l who is an electrician and he said 10g is the minimum acceptable for a run like that but could always go bigger.

Honestly I was surprised. I would have thought to go 80' you'd need at least 6 or 8 ga for 30amps.

Learn something new everyday...

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[traveldawg]

Thank you for the explanation of how an autoformer works. In my original post I tried to explain that my wire run from the sub panel to the pedestal is very long, over 80 feet so I am experiencing quite a bit of line loss. Will the amperage increase in the run from the panel to the pedestal when using the autoformer?

With the Autoformer (or any transformer): when voltage goes up, current goes down )proportionally). So you don't really get 30amps anymore when the Autoformer boosts the voltage. Since we are usually only worried about the voltage it's normally OK for us to use these devices. But ya have to know you don't have 30 amps anymore if the voltage is boosted.

Personally, I think 10 gauge wire is at least one size and maybe 2 sizes too small. Go online and find some wire gauge sizing guides and calculators. One I found said a 10 gauge copper wire, 80' run will loose almost 5 volts versus a 6 gauge, 80' run will loose only about 2.4 volts.

What is the voltage at the source (circuit breaker) for your run?

[CoChris]

Thank you for the explanation of how an autoformer works. In my original post I tried to explain that my wire run from the sub panel to the pedestal is very long, over 80 feet so I am experiencing quite a bit of line loss. Will the amperage increase in the run from the panel to the pedestal when using the autoformer?

Lots of good information above but the full and complete answer is very complex. In very very simple terms, two things to keep in mind

1) In a single wire (like your run from your subpanel to the trailer), current is constant. Voltage drop will be a function of the wire resistance (mostly temperature and length) and current (V=IR). If you have no load (no current) you will have no voltage drop and the voltage will be the same at both ends of the run. If you have different voltage with no load, you do have a load somewhere.

2) If voltage is low at the input to your house, contact your utility (as others have said). If the voltage drop is inside your house/run to trailer you need to increase your wire size or decrease your load. Plain and simple.

3) In answer to your original input/output voltage and current question (will the autoformer increase the input current?), in short yes the input current will increase proportional to the increase in output voltage. i.e If the autoformer boosts the output voltage 10%, figure the input current will increase 10%. There are a lot of factors the go into the complete answer, but this is the safest (most conservative) approach. The fact that some reactive loads (like motors in A/C units) draw less current at higher voltage may mean that the input current does not increase , but may even decrease with boosted voltage, but that is no guarantee. Also, no transformer is 100% efficient, so input power (volts*current) will always be higher than output power). The closer you get to saturating the transformer (maximum current it can handle) the lower efficiency. The best way to know is to measure your actual current draw in the line.

You are asking a good question, but is has a very complex answer.

Chris

[Mr. Goodwrench]

Thanks to all for your responses. Since I won't have time or the money for that matter to run all new heavier wiring to the trailer, I might just drag out the generator for my company to use if they want AC. Not convenient for them but hey, it's my trailer and they are guests! Take care and happy camping.

[Jerryr]

A 30 amp Autoformer WILL WORK for you in your situation.

I visited a friend at his farm and was plugging into a 30 Amp RV outlet at his barn with a 200+ foot run of #10 wire from breaker box. When my AC turned on my EMS shut down my electric to my RV due to voltage dropping below 104 volts.

I bought a 30 amp Autoformer and it resolved the problem bringing voltage up to 114 volts with AC running. The 30 amp breaker at the barn panel never tripped. My EMS was showing 24 amps at peak. BUT I couldn’t run microwave and ac at the same time.

I left the Autoformer with him as a gift. He normally left his class C plugged into that receptacle. He previously had 2 ac motor failures in his Class C which I suspect was due to low voltage. Since his class C has been plugged into the Autoformer for the last 2 years he’s had no further issues. That’s with his refrigerator and ac running all the time. He’s also not had any issues with failed motors or tripped breakers since using the Autoformer.

I bought a 50 amp Autoformer that I keep in our Reflection to use when we travel. I use it only when needed if voltage drops below 110 volts under load.

[jw^2 family]

So would it be accurate to say that if the Autoformer is boosting voltage to the trailer, then you might only be able to draw 27 amps or so (or some other current that is less than 30 amps) inside the trailer before tripping the 30 amp circuit breaker at the house?

[el Rojo]

Lots of good information above but the full and complete answer is very complex. In very very simple terms, two things to keep in mind

1) In a single wire (like your run from your subpanel to the trailer), current is constant. Voltage drop will be a function of the wire resistance (mostly temperature and length) and current (V=IR). If you have no load (no current) you will have no voltage drop and the voltage will be the same at both ends of the run. If you have different voltage with no load, you do have a load somewhere.

2) If voltage is low at the input to your house, contact your utility (as others have said). If the voltage drop is inside your house/run to trailer you need to increase your wire size or decrease your load. Plain and simple.

3) In answer to your original input/output voltage and current question (will the autoformer increase the input current?), in short yes the input current will increase proportional to the increase in output voltage. i.e If the autoformer boosts the output voltage 10%, figure the input current will increase 10%. There are a lot of factors the go into the complete answer, but this is the safest (most conservative) approach. The fact that some reactive loads (like motors in A/C units) draw less current at higher voltage may mean that the input current does not increase , but may even decrease with boosted voltage, but that is no guarantee. Also, no transformer is 100% efficient, so input power (volts*current) will always be higher than output power). The closer you get to saturating the transformer (maximum current it can handle) the lower efficiency. The best way to know is to measure your actual current draw in the line.

You are asking a good question, but is has a very complex answer.

Chris

Can I get you to explain this another way? Let's pull the panel off the pedestal and put an induction amp meter on the neutral wire. Let's assume only one breaker.

Without the Autoformer and the AC is on, the voltage in the trailer read's 108 volts. Let's say the induction meter reads a 13 amp draw.

Now with the Autoformer and the AC is on, the voltage in the trailer now reads 116 volts. Are you saying the induction meter would read a higher amp draw then the previous 13 at the pedestal? Therefore pulling more current from the house?

On Edit. We need to move the induction meter to the breaker that supplies the pedestal.

Red

[JKellerJr]

Can I get you to explain this another way? Let's pull the panel off the pedestal and put an induction amp meter on the neutral wire. Let's assume only one breaker.

Without the Autoformer and the AC is on, the voltage in the trailer read's 108 volts. Let's say the induction meter reads a 13 amp draw.

Now with the Autoformer and the AC is on, the voltage in the trailer now reads 116 volts. Are you saying the induction meter would read a higher amp draw then the previous 13 at the pedestal? Therefore pulling more current from the house?

On Edit. We need to move the induction meter to the breaker that supplies the pedestal.

Red

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.