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Old 05-29-2015, 09:16 AM   #21
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X3, I would have preferred the autoformer. I had a hard enough time spending the money on the PI.
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Old 05-30-2015, 04:57 PM   #22
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The biggest issue with the Franks Autotransformer is it robs Peter to pay Paul affect. You may be okay but your neighbors are paying the price. It robs them of amperage and voltage and makes their power issues worse.


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Old 05-30-2015, 06:40 PM   #23
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Quote:
Originally Posted by wrapperman View Post
The biggest issue with the Franks Autotransformer is it robs Peter to pay Paul affect. You may be okay but your neighbors are paying the price. It robs them of amperage and voltage and makes their power issues worse.

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I am not an Electrical Engineer (but did Minor in Physics), but I do know that the pedestal is fused at 30 amps and I can never pull more power than that without tripping the circuit breaker.

What comes into the autotransformer is whatever voltage is available at 30 amps draw maximum.

What the autotransformer does is take some of that 30 amps (about an amp at full boost; leaving 29 amps available to the camper) and convert it to voltage to boost the voltage delivered to the camper. So if you are "stealing" from anyone you are stealing from yourself.

Because you are paying for 30 amp service you are "taking" nothing away from your neighbors and you are only helping yourself.

While you may have less available amperage, your inductive equipment (Air Conditioner and Microwave) needs less amperage to run than trying to operate it at the lower voltage. (Watts=Volts times Amps with Watts fixed in an inductive circuit)

Example: A 12 RA (running amp) at 120 volt air conditioner needs 1440 Watts to run with 120 volts supplied. Since that 1440 Watts is a fixed number in an inductive load; if the voltage drops to 100 volts, the RA increases to 14.4 amps. This can trip the internal thermal protection in the compressor or eventually burn up the compressor motor. We won't even BEGIN to talk about the momentary start up amps required as even at 120 volts that number can exceed 25 amps for a few seconds (not enough; long enough; to trip the air conditioner's 20 amp breaker).

There is benefit to your resistive loads as well (like your water heater as an example). Since the resistance is fixed in a resistive load circuit, the power of the circuit varies by the voltage available.

For example, water heater element with 10 ohms of resistance at 120 volts will use 12 amps (1440 Watts). If the incoming voltage drops to 100 it will drop the amperage used to 10 (1000 Watts effective heating). (V/R=I then P=V*I)

This means your water heater has to stay ON longer to heat the water to the shutoff temperature.
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Old 05-31-2015, 06:03 PM   #24
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I understand it may not be a big issue most of the time but does make a difference.
Here is an interesting article.
http://www.damouth.org/RVStuff/Autoform.shtml
I hope the link works.


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Old 06-01-2015, 04:51 PM   #25
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Quote:
Originally Posted by wrapperman View Post
I understand it may not be a big issue most of the time but does make a difference.
Here is an interesting article.
Autotransformer Use: "Stealing Power?"
I hope the link works.


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This is a Blog.

This quote says it all [B]"Stealing" may not be the right word.[/B]

Not only that but he makes a string of bogus assumptions:

"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."


In fact he further decays into nonsense with "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."

This would not occur since the voltage drop would be less at the first campsite and get worse as you go along the circuit run due to the increased resistance in the aluminum wire length to the source.

Voltage at your site could be radically different than your neighbor down the row based on the distance between sites and the supply transformer.

It gets even more bizarre when he postulates that by using less than the 30 amps at your site, it is somehow your fault that the campground's wiring can't handle the load they advertise.

He also talks about running his AC at 98 volts for days. What hooey. My AC just grunts at 90 volts and won't turn over.

I believe he just does not want to spend the money to buy one and trash talks folks who care about their equipment and do own one.
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Old 06-02-2015, 11:31 PM   #26
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With all due respect, in your reply are you assuming that there would be adequate amperage to make up the lower voltage, if so then autotransformers would be okay? But when power companies create brownouts, so they can manage power requirements, it gives campgrounds lower voltage which in turn feeds all transformer in the park lower voltage, which then makes the transformers output lower voltage.
The issue I have with autotransformers is when there is a limited amount of power, such as in a brownout. The autotransformers will give the owners of them adequate power (watts) by consuming enough amps. During a brownout a circuit only has limited amount of power and it must be divided equally among all users.
If a branch has 10 users and each one uses 3,600 watts (120 volts and 30 amps) then the total would be 36,000 watts. In a brownout the branch will drop in voltage meaning the total power (watts) will drop. If the total power drops to 30,000 watts for the branch (100 volts x 30 amps) then each site would only have 3,000 watts each. When a person has an autotransformers then they will indeed get 3,600 watts but will leave the other 9 sites 26,400 watts or 2,933 watts each and with the increased load of the autotransformer it will bring the voltage down further complicating the problem. Now if 2 people have autotransformers then the people with them will each consume 3,600 (7,200 watts) and each of the 8 others would now share 22,800 watts or 2,850 watts each. (Actually lower because of the new load on the branch). Now when each person that doesn't have a transformer their amperage increases because of lower voltage causing even more voltage drop. Now when the voltage drops, it causes the autotransformers to draw more power complicating the scenario even further.
I believe there is a misconception with autotransformers for the fact when there is a brownout the people that have them will let everyone else know how they didn't have any trouble running induction appliances. The ones without them have issues, which may imply they would work for all. If everyone had them then no one would have power. A brownout is when a power company limits wattages to certain areas. There is no way around making everyone have equal wattage in a brownout.

Now if the issue with a brownout is the campground fault then they do need to correct that, but when it is a power companies fault it would not be good for me because my PI would just turn my power off. Though, the people with the autotransformers would always be able to meet their power requirements.

This may be why campgrounds don't like them.

Or am I missing something?
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Old 06-03-2015, 06:47 AM   #27
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Quote:
Originally Posted by wrapperman View Post
The autotransformers will give the owners of them adequate power (watts) by consuming enough amps. During a brownout a circuit only has limited amount of power and it must be divided equally among all users.
Watts will always be the same. Slightly lower voltage is compensated for by slightly higher amperage.

Since campground circuit protection is controlled by amperage detecting devices (circuit breakers) and not wattage detectors, low voltage can ruin your camper's inductive motors and electronics before any breaker lets go.

If there is too much amperage (at whatever voltage) being drawn the circuit will go down.

As to the statement regarding every camper using "the same amperage" is just bogus on its face. Many in this situation will still try to heat their water and fridge "with the campground's power" regardless of the brownout.

If the autotransformer is in boost, my fridge and water heater are on propane and I will bet I am using less amps than my "fellow campers."
I do not believe in "sharing the pain" when I have a way to protect myself.
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Old 06-03-2015, 08:47 AM   #28
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Surge Protection or Electrical system Protection

Though doesn't it hold true when voltage goes down amperage goes up? The transformer for any given branch can only put out so many amps and when that is exceeded voltage drops.
When the power company (this is what I am referring to) cuts voltage an autotransformer will then increase its amps input to raise its voltage output. On any given day this power issue would not be a problem, it is when the power companies lower the voltage to meet demand.
One RV on an autotransformer (on any given branch) is okay but if everyone thinks that having an autotransformer (on any given branch) will solve low voltage issues, then that would not hold true. This may be why campgrounds frown upon them. Though your sites 30 amp breaker may not trip to many on a branch will trip the main transformer circuit breaker.

Thanks for the replay cause this subject is very interesting to me. I have always been curious to all of the comments made on electricity whether it be 12, 24, 120, 240 or whatever power it may be.

I am no expert on this subject but enjoy learning.

Putting all this aside I hope you are enjoying RVing season. Do y'all travel or mainly stay at a few locations? Do you attend Goshen's rally. I hear they are already booked solid. That's too bad cause my DW and I were trying to make it this year.
I hope our travels cross paths in the future.
Sincerely,
Bob
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Old 06-03-2015, 12:31 PM   #29
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I recently experienced low voltage incident at an rv park. First day was fine but the second day my progressive electrical system protection disconnected our power whenever my wife turned on the coffee maker. I checked the progressive unit and it read 107 volts. Was an issue the rest of the trip. We couldn't run the microwave and watch TV. So I just ordered a Hughes autoformer to have on hand for the next trip. We are going on an 8k miles, 3week road trip and last think I want is to have power issues if I can help it.
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Old 06-03-2015, 06:58 PM   #30
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At one time I thought about buying one but I have never had an issue with brownouts and if I do I will just run the generator till power is restored to where it needs to be.
I have too many other items to buy and my DW says I only have so much money to spend a month.
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