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Old 09-04-2012, 08:43 AM   #1
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Autoformers and the National Electric Code?

I found this National Electrical Code copied on another forum and don't have access to the code myself. If this is accurate then how can these companies continue to sell autofomers to people for their RV's? I was going to buy one but not if they are against the electrical code. I doubt my insurance would even pay for my trailer should it burn down if I had one of these hooked up?


NFPA 70 - National Electrical Code® 2011 Edition

Chapter 5 - Special Occupancies

Article 551 - Recreational Vehicles & Recreational Vehicle Parks

Section 20 - Combination Electrical Systems

Paragraph E - Autotransformers

"Autotransformers shall not be used."


For those that don't know what autofomers are used for they are used to boost voltage in trailer parks that don't have a good power source. Autofomers will automatically increase wattage by lowering amperage.
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Old 09-04-2012, 08:47 AM   #2
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Will need to check that out.

There are lots of vendors of these systems and the electrical code for campers is the RIVA one. Not sure what that one states.

Thanks for tracking that post down.
I will do some investigating.
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Old 09-06-2012, 12:02 PM   #3
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I received an answer back from the distributor of the Powermaster Autofomers that I've posted below. He says what they sell are step up transformers and not autotransformers. So it looks like what they sell are acceptable. I don't think they'd risk selling something that wasn't.


"You have correctly identified the section in the NEC code for the rules on the use of Autotransformers in RVs.

This rule is for Autotransformers, NOT step up transformers. There is a huge difference in these two devices. PowerMaster Voltage Controller, as well as all of it's competitors utilize step up transformers.

The transformers in voltage boosters for RVs and other applications are NOT automatically variable. They have fixed taps on the output side of the transformer. Selection of which tap to activate is made by the internal controls of the voltage booster.

This is a brief description of a modern voltage booster for RVs. Some designs have a much better reliability factor than others. PowerMaster Voltage Controllers have the lowest failure rate in the industry. Only two manufactures of voltage boosters are rated to be installed inside of an RV. They are PowerMaster Voltage Controllers and the Hughes Autoformer.

It appears you are confusing the trade name Autoformer (which is owned by Hughes Autoformers, Inc.) with Autotransformer.

I hope that this explanation clears up this misconception."
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Old 09-06-2012, 01:06 PM   #4
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I see he can still twist the truth to suit his needs.

Ask him about the patent lawsuit he lost to the manufacturer of the Franks unit. He is supposed to be "out of business" as I understand it.

Although to be fair, I got that from the owner of Franks Electronics.
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Old 09-06-2012, 07:23 PM   #5
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Question

Quote:
Originally Posted by herk7769 View Post
I see he can still twist the truth to suit his needs.

Ask him about the patent lawsuit he lost to the manufacturer of the Franks unit. He is supposed to be "out of business" as I understand it.

Although to be fair, I got that from the owner of Franks Electronics.
I've heard that too. Anyway I was giving him the benefit of the doubt on the autotransfomer until I research it further.

I don't really know what you'd call a transformer that steps up the voltage or lowers it automatically other than an autotransformer since that's what the autoformers do.
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Old 09-06-2012, 08:04 PM   #6
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Originally Posted by Happytrails2U2 View Post
I've heard that too. Anyway I was giving him the benefit of the doubt on the autotransfomer until I research it further.

I don't really know what you'd call a transformer that steps up the voltage or lowers it automatically other than an autotransformer since that's what the autoformers do.
Too right. I am still waiting to hear the verdict of your research.
I just would not quote "that guy" as an expert at anything except ripping off other people's intellectual property.
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Old 09-06-2012, 08:34 PM   #7
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I thought an Auto Transformer changed the output voltage as a result of the current being drawn thru the coil. A step up transformer is fixed and can only be adjusted by physically changing taps on the transformer. Sounds fishy. My code book is at my office but I will look up the chapter.
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Old 09-06-2012, 08:56 PM   #8
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Same chapter & verse in 2008 NEC which I have electronically here.

It is referring to equipment sold with or integrated into the RV by the RV manufacturer, not add-on equipment. However it may also be applied to aftermarket equipment, of that I am not certain.

An autotransformer typically has a single winding and portions of this are used as both primary and secondary coils.
A transformer (step up, down, or isolation) typically has two distinct coils, often with taps to vary input/output ratios.

An auto transformer does not provide isolation between its windings as a standard multi-coil unit does.

Refer to Wikipedia-autotransformer-Limitations

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Old 09-06-2012, 10:15 PM   #9
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Autotransformer - Wikipedia, the free encyclopedia

This does explain it quite well.
An autotransformer IS a step up/down transformer.
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Old 09-06-2012, 10:22 PM   #10
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Quote:
Originally Posted by herk7769 View Post
Autotransformer - Wikipedia, the free encyclopedia

This does explain it quite well.
An autotransformer IS a step up/down transformer.

TRUE.
Patato ...Potato they are both french fries.

They can also say it is a temporary mobile device that is not attached to a RV or the campground owned so it doesn't fall under that NEC
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