AMTRAK Car Electrical System

Status
Not open for further replies.
dkidd

dkidd

Senior Member
Location
here
Occupation
PE
I recently took AMTRAK to Washington for work. There are 120 volt three wire convenience outlets at each seat. Having recently attending a Mike Holt Code Changes seminar, I had gotten a great deal (free) on an AEMC Outlet/GFCI tester. I was guessing that the outlets would be GFCI protected. When I plugged it in, only the center yellow indicator lit, indicating no ground. I took it into the restroom where there is a GFCI receptacle, and it didn?t have a ground either. Pressing the test button did not trip anything, since there was no connection to the ground prong.
Information I found on AMTRAK car wiring states that the system is a 120 volt ungrounded delta, and that the outlets are GFCI protected.

NEC states that it does not apply to rolling stock.

Very strange. I?m still trying to figure out if it is safe or not, and whether the GFCIs would ever trip.

Any thoughts?
 
Yes, the GFCI would trip if it sensed an imbalance of current between the hot and neutral conductors.
 
dkidd said:
I’m still trying to figure out if it is safe or not, and whether the GFCIs would ever trip.
Click to expand...
Run a 4 w or 7-1/2 w incand. bulb from the short outlet slot to any nearby metal. If the bulb stays lit you're not protected.

And outlet testers lie, sometimes on important issues. There are about 30 ways to incorrectly hook up a 3 slot outlet and only one right way.
 
If the source is genuinely ungrounded, a bulb won't between either wire and ground, and a GFCI would neither work nor be necessary.
 
I have no idea how a rail car is built but assuming a metal car, unless the car is isolated from the wheels, I would think there would be ample path to ground. Otherwise, couldn't a rider who somehow managed to contact the hot conductor just sit there, energized to 120 volts?
 
Last edited:
sii said:
I have no idea how a rail car is built but assuming a metal car, unless the car is isolated from the wheels, I would think there would be ample path to ground. Otherwise, couldn't a rider who somehow managed to contact the hot conductor just sit there, energized to 120 volts?
Click to expand...

The 'source' is a generator on board that likely is not bonded to the trains metal parts. The fact that the metal parts will have a connection to 'dirt' is irrelevant.
 
What about capacitive coupling between the generator housing?

In any case, how do you reconcile
"
I took it into the restroom where there is a GFCI receptacle, and it didn’t have a ground either. Pressing the test button did not trip anything, since there was no connection to the ground prong.
Information I found on AMTRAK car wiring states that. . . the outlets are GFCI protected.
NEC states that it does not apply to rolling stock.
"
?

Is GFCI being used as a buzzword to comfort passengers who are somewhat knowledgeable, a placebo?
 
G._S._Ohm said:
In any case, how do you reconcile
"
I took it into the restroom where there is a GFCI receptacle, and it didn’t have a ground either.
Click to expand...

A plug in GFCI tester will never trip a GFCI without a ground present, this applies regardless if it is a home or rolling stock.

The correct way to test a GFCI is by using the test button on the device, if the device is operating properly it will trip even without a 'ground'.

As far as the capacitance coupling ..... if it raises to dangerous levels and someone gets between the load side of a GFCI and the metal train the GFCI will trip. If the capacitance coupling is low the GFCI would not trip but would not be needed either.
 
sii said:
I have no idea how a rail car is built but assuming a metal car, unless the car is isolated from the wheels, I would think there would be ample path to ground.
Click to expand...
The shock hazard can only exist between one source conductor and a surface connected to another source conductor (of a different potential.)

Otherwise, couldn't a rider who somehow managed to contact the hot conductor just sit there, energized to 120 volts?
Click to expand...
Like the bird on the wire, there's no potential difference, thus nothing to drive current. An unconnected earth is of no relevance.
 
iwire said:
The correct way to test a GFCI is by using the test button on the device, if the device is operating properly it will trip even without a 'ground'.
Click to expand...

A GFCI tester works by connecting a resistance from the phase prong to the ground prong. Without a ground, it will not trip.
 
If the system is not grounded there will be no potential between system conductors and ground (ground in this case is the frame of the car and not necessarily earth).

If you have a fault to ground on one of the system conductors then that conductor becomes grounded although not intentionally. The system still operates without causing shock hazards other than between the other system conductors and grounded objects which are at same potential as the conductor that became grounded. If a second system conductor becomes grounded you will then have a short circuit.

There hopefully is equipment that monitors for ground faults and alerts operations people that there is a problem. It really is not that much of a hazard to operate with one fault but the problem should be looked into and repaired as soon as reasonalby possible.

This same protection system is used in some processes where shutting down because of a ground fault may cause more harm than good - it gives operators a warning that there is a problem and allows an orderly shut down instead of instant failure.

Many portable generators are not bonded to the neutral either. There is no potential to ground until a conductor becomes grounded - then there is potential from the other conductor to earth. And they install GFCI's on these generators that really are not needed. Unless the generator is conncted to a premises wiring system - then the generator frame will be bonded to the generator neutral through the equipment grounding conductor and the system bonding jumper at the premises service equipment.
 
{Moderator's Note}
I deleted this post for two reasons. First, we don't allow "link dumps," meaning posting a link to some other web site without giving some explanation of where that link will take you. Secondly, that link brings up a document that may provide enough information to answer the original question. But every page of that document declares itself to be "Confidential, not for distribution." We don't allow violation of anyone else's copyrights or other intellectual rights.
 
Last edited by a moderator:
AMTRAK Car Electrical System

Sorry for not contributing for some time but buisness and family requirements were most important.
Re;the initial question posed here-Gfi/recpt rules would appear in violation if judged by use of a 'Standard Tester'
The reason for 90.2{1} --in this case regarding 'Rolling Stock/Railways' with regards to areas not covered are many--
It is not just to give utilities,Railway services,Airlines,etc. a free pass--It would seem to me that it is also to reflect that the areas in question do not always conform to the same dedicated set of parameters which we can apply when dealing with a set land based installation.
Additionally--as to why a tester may not show an initial easy answer as to what you are seeing--we must always remember that there are many conditions which can exist,can have been corrected as per code and yet 'just sticking in our tester' will not give us all the info we need.
A 'tester'of any sorts,and we have many at our disposal,is only one step in figuring out what you may be looking at.
 
Please correct me if I am wrong, but Kwired answered the question didn't he?
Or am I crazy? ---Lol please don't answer that!!!
He did forget to add that once the first fault happens, that this make the GFI receptacle
functional. Maybe this is what the Engineers had in mind.
 
Status
Not open for further replies.
Top