Autoformers and the National Electric Code?

[Happytrails2U2]

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.

[Herk7769]

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.

[Happytrails2U2]

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."

[Herk7769]

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.

[Happytrails2U2]

Originally Posted by herk7769

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.

[Herk7769]

Originally Posted by Happytrails2U2

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.

[wfmdfm]

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.
Wally

[Bennington Camper]

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

-Glenn

[Herk7769]

Autotransformer - Wikipedia, the free encyclopedia

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

[Iggy]

Originally Posted by herk7769

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

[Happytrails2U2]

The Powermaster guy says they're not autotransformers but rather voltage boosters.

Sounds like calling an automobile a car in my opinion.

[Bennington Camper]

The big difference is isolation in case of a failure in the windings.
There is no galvanic isolation in an autotransformer.

Originally Posted by herk7769

Autotransformer - Wikipedia, the free encyclopedia

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

[VinceU]

Originally Posted by wfmdfm

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.
Wally

Autotransformers are actually most often used to step down voltage usually for a short period. They are wound with a single core of laminated iron, with a single winding which may be hundreds of turns of wire. The supply power to the winding and and using the same common at the bottom of the winding, they can "tap" the same winding at multiple points and take off lower voltages right on up to 15% higher voltage as the supply. They are "auto" only because its fabricated of one winding not two. When used for short voltage drops it can used to start large motors which need a lower starting voltage to prevent overloading the power supplys.
Transformers have two windings and up to 3X more “iron” laminations, are normally used to step up or down voltages for continuous use. They are considerably heavier and costlier than these RV type step ups. The quote above was playing games with terms, I don't think the average RV'er could lift and stow a standard transformer of these ratings.

Autotransformers with built in VR for up to 3 taps do it with electronics, the input voltage controls the output by switching taps. All this luxury costs power to provide. The xfer itself has not only resistive load but also plenty of reactive load (apparent power) which are a direct load on the 30 supply, something you are trying to preserve. Transformers are not the most efficient sources of electrical transmission esp the auto style. Maybe this is why the mfgrs don’t publish the losses.

I would not discount or rule out the NEC guides to banning them. That was published for a good reason and should be discovered. Personally I don’t carry one, My theory is if the campground has low voltage time to refund and check out. I have a triple meter 2DC and AC meter at the door of my RV and can tell at glance if power is NG. Normally I don’t find low voltage in the camps I frequent, admittedly have not done state parts in quite some time. If you are paying 35 to 50 a night you should have sufficient power.

I have seen myself the failure of two autotransformers used in motor starting. The problem is when they fail, they can self ignite the varnish/epoxy insulation before the breaker can trip. They then continued to burn feeding on liquid insulation causing smoking hot localized fire. Perhaps this is why NEC banned them, don’t really have firm answer though.

Just food for thought.

[Herk7769]

Long talk with Frank yesterday.

Long story (no kidding) short; the RV autotransformers are not UL rated.
They want 10,000 bucks per unit rated.
He is not aware of any units being sold that have the rating.

If you "install" the unit while retaining the socket and plug connections it is not considered "permanent" according to the code.

Update on Powermaster.

He stole his designs from Hughes mostly and two circuits from Frank.
He was not sued by Hughes or Frank because he was convicted and sentenced for stealing and selling satellite TV service.

[bob213]

So is PowerMaster out of business?

[Herk7769]

Originally Posted by bob213

So is PowerMaster out of business?

Supposedly. Who knows what he is doing and with whose stuff.

[Happytrails2U2]

Originally Posted by herk7769

Supposedly. Who knows what he is doing and with whose stuff.

I thought he was only the distributor not the manufacture.

[bob213]

It's hard to tell since his website is still active. But...Burro travel trailers site is still up so I guess that doesn't tell us much.

[Herk7769]

Found out he worked in sales for Hughes Autoformer and was terminated. He took circuit design info when he left. He also took apart an early Franks unit and tried to reverse engineer an Autotransformer that used the best of both. Apparently his bashed design did not have enough from each to make a case for either. While Hughes and Frank's were in talks to combine forces, Todd (Powermaster) was arrested and convicted for stealing and selling satellite service boxes.

If he is still selling his Autotransformer, it was news to Frank at Frank's Electronics.

[BarryD0706]

FYI, read in another forum of someone ordering a PowerMaster directly from Todd yesterday. He's still in business.