I almost electrocuted an engineer on the layout yesterday.

Thank you for posting.  Valuable warning.

That's the thing about PW transformers, the standards for insulation were not like they are today, and many people have been inside mucking around with repairs.  Add to that they're not grounded, and you have to be considerably more careful than with modern stuff built to newer safety standards.

It's been years since I opened a PW ZW.  I will accept as factually correct, JP's statement that, " When the handle is in the off position,  the carbon roller rests on a flat piece of metal which is the frame of the X-former."  I was thinging that it would not be difficult to convert the power cord to a 3-wire system, connecting the green to the frame.  However, this statement leads me to conclude that would not be a good idea, because then you could have a portion of the layout connected to the 120-volt main's green, which could create a hazard.

A bigger issue connecting the transformer to a 3-wire system.  If any of the secondary windings are in any way connected to the 3rd ground wire from the outlet, you have killed the TMCC signal.  It also makes it more difficult to phase the transformer since you can't reverse the plug.

@RJR posted:

I was thinging that it would not be difficult to convert the power cord to a 3-wire system, connecting the green to the frame.

it has been shown many times by knowledgeable experts on this forum and elsewhere that adding a 3 prong plug and grounding classic Lionel transformers is just outright WRONG and not proper way to achieve safety. I get it, sure, to the layman, it seems like adding a 3rd prong and grounding things is the right thing to do, but then look around, what other train transformers, even current production ones have a ground? See https://ogrforum.com/...y=148675927400293147

Furthermore, the current modern UL specifications for Toy Transformers in section 16 of specification 697 state that the cord, plug and unit should NOT be grounded, at least 18 gauge in size, between 5 and 10 ft long and not detachable from the transformer. I can't directly quote the source because it is copyrighted, but one can purchase their own copy: https://standardscatalog.ul.co...aspx?productId=UL697   Also, lets remember, that Lionel classic transformers were UL listed when appropriate.

The correct way to achieve increased safety is as simple as using the correct unpolarized plug and introducing an upstream GFI. This can be done by installing a GFI wall outlet, or using a device like this: https://www.amazon.com/TRC-Sou...4637550-2400668?th=1

One can even elect to have the GFI built into the transformer power cord, maybe something like this: https://www.amazon.com/Replace...tioner/dp/B077FV6RQT However, even still with this type of cord, one still should NOT ground the transformer case.

Asa a non TMCC user, that would not be a problem.  As for changing the phasing, I have gone into transformers and reversed the 2 line cord conductors.  When replacing cords, I always make phasing part of the process.

I agree that working on the 120-volt wiring is not a task for the inexperienced/uneducated.

@RJR posted:

Asa a non TMCC user, that would not be a problem.

Try to remember you're posting "solutions" here, and this "solution" would be a very bad idea for a number of reasons, TMCC compatibility being one of them.  A lot of folks here DO run TMCC/Legacy.

The ZW design does not support a ground wire solution and it should not be done. Occasional inspection of the power cord, GFI protection, and a power strip with a master switch should be all that is needed for safe use.  A comment the OP made did catch my eye.  The roller on the ZW should roll on to a piece of fish paper in the off position. If it rolls on to the metal frame a harder look should be made of this transformer.

@David Johnston posted:

The roller on the ZW should roll on to a piece of fish paper in the off position.

I don't recall fish paper - so I took a sampling of my ZW and VW transformers and even an online search and find this arrangement:

That highlighted roller resting surface is not fish paper and not metal. Perfectly fine and normal for the roller to rest on that nonconductive surface in the OFF position.

A number of older transformers had metal cases. If one of the conductors of the power cord should happen to make contact with it, there would be a hazardous situation.  Perhaps the addition of a 3-wire cord with the green fastened directly to the case, would be appropriate.

I do agree with David Johnston that the design of the ZW does not lend itself to a ground wire.

@RJR posted:

A number of older transformers had metal cases. If one of the conductors of the power cord should happen to make contact with it, there would be a hazardous situation.  Perhaps the addition of a 3-wire cord with the green fastened directly to the case, would be appropriate.

As I laid out in my post above, one should not willy-nilly add a ground to devices not engineered for an earth ground.

I certainly do not recommend doing anything willy-nilly.  I also would not rely on a UL certification issued 80-90 years ago as meaning an item is safe.  I believe it was only in the 1940s or later that three-prong plugs made an appearance.  I remember I was along in years when they first became common.  When they appeared, I remember there was a rush to buy "adapters, which often came with a small wire to slip under the receptacle faceplate screw.  Of course, this may have been useless, since three-wire systems in houses were not code-required 80 years ago and they may or may not have had BX cable so wired as to serve an equivalent function.  (If I recall the house I grew up in, it used BX cable, the shell of which was (supposed to be) grounded to steel receptacle box.  Since the receptacle was held to the box with screws, supposedly the steel frame of the receptacle was grounded and this made contact with the faceplate screw.

I have seen much incorrect or contested information published on the subject of grounding published by apparent gurus.  For example, several decades ago a prominent boating organization published an article saying that boat owners should clip the grounding prong off all plugs.  Author's theory was that if someone was holding an item that was connected to hot (black) and touched an appliance or device whose shell was grounded (to green), they would be electrocuted, which is true. They later withdrew that recommendation after a hail of criticism.

Without getting into the weeds here....

Some light reading

https://www.iaei.org/store/vie...uct.aspx?id=16304241

It's important to remember that our "toys" are connected to 120v household wiring. If you are not sure about something, call a professional. You never know, you might find a new train buddy in the process.

@RJR posted:

I also would not rely on a UL certification issued 80-90 years ago as meaning an item is safe.

The UL spec cited is current. I never stated a dated UL certification is equivalent to a modern one or that it provides the safety of one.

@RJR posted:

three-wire systems in houses were not code-required 80 years ago

So you end up with devices engineered without consideration for earth grounding.

@RJR posted:

several decades ago a prominent boating organization published an article saying that boat owners should clip the grounding prong off all plugs.  Author's theory was that if someone was holding an item that was connected to hot (black) and touched an appliance or device whose shell was grounded (to green), they would be electrocuted, which is true. They later withdrew that recommendation after a hail of criticism.

Removing grounds from a device engineered to be grounded was framed to make sense just as your thought to add a ground can make sense in a certain frame.

Bottom line, I highlighted and advocated for an (modern) UL/NEC (and just about whatever) acceptable solution for those who wish to use classic transformers with an added element of improved human safety.

If you look there is no UL marking on the post war ZW as the wattage rating exceeded the requirements of the UL standard.  Now, surmising the same engineers designed the UL approved transformers, the internal construction of the ZW would be to the same standards.

BTW, before retiring, I spent 45 years dealing with UL and was on a UL/industry committee that revised the standards for air conditioning equipment. Every  requirement in the standards is rigidly researched and involves the relevant industry representatives. 

Joe, I agree one should look for the UL designation.  The engineers probably became wiser as they aged, so I won't assume pw Z W designed as well.

There is truth to what @CSXJOE says. At the introduction in 1948, the VW was UL certified, the ZW wasn't. The only difference in construction was the transformer core and nameplate. Thus one can reasonably be assured the transformer was constructed to UL standards as applicable and just that UL didn't have an applicable class for such a powerful product.

Here is the UL label on a VW:

Now, the ZW, despite not having UL certification out the door, did meet localities requirements such as these:

As an aside, even metal cased transformers like this RW are UL certified:

Interesting post, bmoran4.  I did not recall that the VW was UL approved.  Also interesting was the local seals of approval.  I wonder how those municipalities enforced the requirement for their own approval.

I wonder how safe are those old metal-cased transformers, like my 1941 Type R.  The insulation on the internal wires shows signs of aging, and if one should touch the frame, there could well be a hazardous situation.

@RJR posted:

I wonder how safe are those old metal-cased transformers, like my 1941 Type R.  The insulation on the internal wires shows signs of aging, and if one should touch the frame, there could well be a hazardous situation.

Hence the recommendation for competent servicing including evaluation and replacement of the power cord and the urging to have an upstream GFI. The GFI will trip at 4-6mA leakage current. Usually 10mA is considered annoyingly painful and 100-200mA is generally considered fatal. Should a transformer fault form and conduct current through a human, the GFI offers much improved life saving safety protections.

Now, revisiting the (not recommended) idea of earth grounding the metal case and developing a fault causing the case to become live, the slow typical 15A or 20A house breaker would need to trip and has a much less favorable outcome in the event of human conduction.

With regard to your last paragraph, the breaker should open as soon as the hot wire contacted the case.  If a case is grounded (green) , it is not the person touching it that causes the current flow.  And if the case does get contacted by the hot wire, you are better off if the case is grounded than not, since there will probably be a  better connection to ground than you.

Your statement regarding competent servicing implies that there is competence.  Unfortunately, competence may be hard to find.  I have had two sons purchase houses, one brand new, where supposedly competent, licensed electricians had left major flaws:  GFIs wired backwards, and a 12-gauge receptacle circuit fed through 20 amp breakers at each end (that took a long while to figure out).  I also wonder whether the insulation on a primary winding lends itself to thorough inspection.

Your statement that 100-200ma is considered lethal is true but misleading.  I've done some studying about GFI usage for marinas, and there is a code requirement for opening in the 30ma range.  But the authorities seem to agree that 30ma causes paralysis, and for personal, as opposed to equipment protection, limit should be 5-6 ma.  I agree that a GFI receptacle is to be recommended for powering a train layout, or upstream on a circuit of several receptacles, and have so recommended in a recent post on the forum.

Whenever I have wired basements, I used a GFI receptacle as the first receptacle on every circuit.

@RJR posted:

With regard to your last paragraph, the breaker should open as soon as the hot wire contacted the case.

The house breakers are designed to protect the wiring, not humans, and have trip times measured in seconds to minutes (dependent upon many factors). GFIs are arguably more focused on protect humans. Use the right tool for the right job and don't go re-engineering things.

@RJR posted:

Your statement regarding competent servicing implies that there is competence.  Unfortunately, competence may be hard to find.  I have had two sons purchase houses, one brand new, where supposedly competent, licensed electricians had left major flaws:  GFIs wired backwards, and a 12-gauge receptacle circuit fed through 20 amp breakers at each end (that took a long while to figure out).

You speak unfortunate truth. Thankfully there are many competent individuals who can service our train transformers (I won't even attempt to mention a few because I'll never get them all!), but I also know there are a few bad apples out there too (I'm not here to name names here either).

@RJR posted:

I also wonder whether the insulation on a primary winding lends itself to thorough inspection.

When I service transformers, in addition to a visual inspection, I always check that the primary is electrically isolated from everything - the frame, the secondary windings and so on.

"The house breakers are designed to protect the wiring, not humans, and have trip times measured in seconds to minutes (dependent upon many factors). GFIs are arguably more focused on protect humans."

You are correct.  And I am certain that you would agree with this statement:  If the hot feed in my type R should internally make contact with the case, when the transformer is plugged in, there is a danger and, if I were to touch the case, I would get shocked and the house breaker would be no protection whatsoever.  A working GFI receptacle would provide protection.

You probably would also agree with this.  I this situation, if the case were connected to green of a 3-wire cord, the breaker should open as soon as the unit is plugged in.

And I agree with your premise:  tinkering with transformer internal wiring is not a job for the inexperienced or uneducated.

When you check a transformer, how can you be sure that the insulation on buried turns is not breaking down?  I suspect that heat does takes its toll upon varnish.

My Type R sits on a shelf near the workbench, and I rarely use it.  I prefer to use a modern unit.

For the benefit of forumites, I would note that a GFI receptacles should be tested at least every 3 months.  Often they do fail.  Some new types do claim to self-test.

@RJR posted:

You probably would also agree with this.  I this situation, if the case were connected to green of a 3-wire cord, the breaker should open as soon as the unit is plugged in.

In an ideal direct short, yes - but in my experience in with probably hundreds of toy transformers, it usually is not a direct short, but a very flakey/intermittent and/or weak one that wouldn't necessarily carry enough current to trip the house breaker in a timely fashion.

@RJR posted:

When you check a transformer, how can you be sure that the insulation on buried turns is not breaking down?  I suspect that heat does takes its toll upon varnish.

Depending upon the type of primary winding short, there are many ways to investigate that are usually a variation on the following:

*Use a very sensitive DC ohm meter on the primary winding to measure the resistance

*Use a very precise primary input voltage and compare a very precise secondary voltage reading and compare to the transformer's mathematical model (winding turn count and such).

Additionally, the circuit breaker of the transformer is tested to be within spec to ensure that overheating hasn't and will not happen.

@bmoran4 posted:

it has been shown many times by knowledgeable experts on this forum and elsewhere that adding a 3 prong plug and grounding classic Lionel transformers is just outright WRONG and not proper way to achieve safety. I get it, sure, to the layman, it seems like adding a 3rd prong and grounding things is the right thing to do, but then look around, what other train transformers, even current production ones have a ground? See https://ogrforum.com/...y=148675927400293147

Furthermore, the current modern UL specifications for Toy Transformers in section 16 of specification 697 state that the cord, plug and unit should NOT be grounded, at least 18 gauge in size, between 5 and 10 ft long and not detachable from the transformer. I can't directly quote the source because it is copyrighted, but one can purchase their own copy: https://standardscatalog.ul.co...aspx?productId=UL697   Also, lets remember, that Lionel classic transformers were UL listed when appropriate.

The correct way to achieve increased safety is as simple as using the correct unpolarized plug and introducing an upstream GFI. This can be done by installing a GFI wall outlet, or using a device like this: https://www.amazon.com/TRC-Sou...4637550-2400668?th=1

One can even elect to have the GFI built into the transformer power cord, maybe something like this: https://www.amazon.com/Replace...tioner/dp/B077FV6RQT However, even still with this type of cord, one still should NOT ground the transformer case.

Setting aside UL requirements, what is the specific hazard caused by grounding the exposed metal parts of a PW transformer?

I would note that many power tools today do not have a grounding wire, and instead rely on additional insulation and a non-conductive case to provide operator safety.  Modern transformers don't appear to have much exposed metal. 

bmoran raises a good point when he speaks of "flakey" shorts.

@PLCProf posted:

Setting aside UL requirements, what is the specific hazard caused by grounding the exposed metal parts of a PW transformer?

Prof,

Your question is right on the mark but I have a feeling that it's best left to a safety engineer.  If you ask a  group of hobbyists, even technically savvy ones, you'll get a hundred opinions but few distinct, professional answers.  This most assuredly NOT a knock on them in any way.  They just don't have the pertinent training, skillset, or experiences to answer your question.

Unfortunately, an answer from a skilled professional or safety organization is what's needed for most of us to be confident in using old transformers in a modern world, and that's the way it should be because, like most technical things, safety engineering has evolved significantly for the better over the last 75 years.

Specifically, who on this forum going to do the Hazard Analysis and Risk Assessment (HARA) for a 1940's or 50's era ZW or RW in order to start the process of answering your question?

Thank you for asking it though.  It is literally to the specific point.

Mike

@PLCProf posted:

Setting aside UL requirements

STOP right there! We hobbyist and "arm chair electrical engineers" are likely not smarter than these kinds of organizations.

@PLCProf posted:

What is the specific hazard caused by grounding the exposed metal parts of a PW transformer?

First, let us all acknowledge that at this point in the post, I am now going to stretch from my comfort of expertise and education. With that honest disclaimer out of the way, I believe one of the reasons may be attributed to the transformer construction style. By grounding the metal base of the ZW (or whatever transformer), you are also grounding the mounts and components of the transformer core. This transformer core was not engineered or designed to be grounded and therefore grounding the arrangement can cause circulating currents within the transformer causing hot spots and overheating leading to a potentially catastrophic and dangerous failure.

I do not understand why anyone would operate an 80 year old device that was originally constructed with paper or a paper derivative as insulation.  And unless all of the ZW transformer experts have "dipped and baked, or VPI'd the core", I would not even plug one in.  You can pay a very high price for nostalgia.  The modern transformer designs are really much better with regard to safety and power.

@Hudson5432 posted:

I do not understand why anyone would operate an 80 year old device that was originally constructed with paper or a paper derivative as insulation.  And unless all of the ZW transformer experts have "dipped and baked, or VPI'd the core", I would not even plug one in.

These valid concerns can be addressed by a competent inspection in conjunction with proper installation and use (all touched upon above). That being said, nobody is forcing anyone to use a classic transformer, but I would hope that the idea here is to engage in good dialog and sharing of valuable information; not to rise to fear mongering and tribalism.

bmoran raises a good point 3 posts above, when he speaks of "circulating currents"  Induction by the windings causes eddy currents that flow within the core.  The core is laminated to reduce these.  They heat the core.  No one is sure what connecting it to additional items would do.

Hudson, because they provide a pure sine wave, have been durable, and are paid for.

@RJR posted:

Hudson, because they provide a pure sine wave, have been durable, and are paid for.

👍

Stupid question: if I plug my (1953) Gilbert/ Flyer 15B  into a power strip with a built-in circuit breaker/ reset button, will that offer (at least) some sort of protection, for the unit and the user?

Mark in Oregon 🎄

To reiterate much of what was covered above:

Circuit Breakers principally protect infrastructure

GFIs principally protects humans

You want both. Amugst all the dialog above, I gave some options for adding an upstream GFI:

@bmoran4 posted:

The correct way to achieve increased safety is as simple as using the correct unpolarized plug and introducing an upstream GFI. This can be done by installing a GFI wall outlet, or using a device like this: https://www.amazon.com/TRC-Sou...4637550-2400668?th=1

One can even elect to have the GFI built into the transformer power cord, maybe something like this: https://www.amazon.com/Replace...tioner/dp/B077FV6RQT However, even still with this type of cord, one still should NOT ground the transformer case.

You are wrong, Mark.  That is not a stupid question.  I may provide some protection to equipment, but provides no shock protection to you.

Thanks. I like the look of that plug-in GFI shown above: thanks for providing that link. 👍

Mark in Oregon

@Hudson5432 posted:

I do not understand why anyone would operate an 80 year old device that was originally constructed with paper or a paper derivative as insulation.  And unless all of the ZW transformer experts have "dipped and baked, or VPI'd the core", I would not even plug one in.  You can pay a very high price for nostalgia.  The modern transformer designs are really much better with regard to safety and power.

Some of us just live with more risk. I expect it is much riskier when I feed my cows or move hay by myself. God forbid the risk when I climb into a deer stand😀 I will take my chances with my zw

Nothing wrong with a ZW, as long as it's been properly repaired.

One has to be careful with UL ratings and electronics with metal cases in the 1950s and prior years.

A friend gave me his dads old 1955 Hallicrafters S-77A , AC-DC short wave receiver.   It worked but I found the metal case and chassis was 110v hot when the with the pluggedthe in one way when OFF and hot with plug in the other way when ON.  This receiver does not have a isolation transformer and has all the tube heater wired in series to add up to 11Ov.  One saving feature was the control knobs are nonconducting plastic or Bakelite.

I got a ALCI (Appliance Leakage Current Interrupter) polarize plug, with reset and test buttons, and cord from a old hair dryer and installed it.  The metal case was not hot then and it worked for a day or two.

Then the tubes light up but the receiver did not receive, probably a bad tube.  It was not worth the effort to find and buy a tube to me.  It takes about half an hour of warm up time to get old tube shortwave receivers to stabilize the frequency drift to be able listen to them.  I am to impatient to wait that long.  That is the reason I sold a better Hallicrafters receiver that we used to listen to US Armed Forces and VOA shortwave when living overseas in the 1970s.

Charlie