Continuity between third rail and either outside railing?

@Raven87 posted:

My first question is, is continuity between the third/middle rail, and the two outside/ground rails common? And if not, how do I find where the issue might be on all of this track? Then my next question is if that is common, why did I see small sparks? I’m not an electrical engineer but somewhat capable but this one has me puzzled.

Steve,

Quite simply no, never.  With nothing on the track and the transformer disconnected continuity between outside rails and the center rail is neither desirable nor tolerable in anyway.  This is by definition a short circuit.

It can happen that the mechanical construction of the track, particularly traditional tubular rail, leads to damage the little fishpaper insulators that are crimped between the center rail and the metal ties.  However this situation doesn't exist with Fastrack.

As a result with Fastrack most often the continuity you speak of would come about because of a wiring error external to the track.  If you're sure that that you've made no wiring error, then you've got to scrutinize the way mechanical parts that make up your problematic Fastrack section are secured to the plastic base and to each other.  One of the metal pieces must be ajar, misplaced or clamped incorrectly by the factory, leading to the short circuit.  Look at it carefully.

BTW -- With the power off you will measure continuity, if the transformer is connected, because a traditional transformer itself looks like a DC short circuit, or at least a low resistance, between the center rail and one or both of the outside rails.

Mike

That’s what I thought.  I had installed a couple more jumper wires to assist with low-voltage areas so I’m guessing I have one of those incorrectly done.
Thanks again.

You can also get continuity if an engine is on the track, even though power is off.

@Raven87 posted:

My first question is, is continuity between the third/middle rail, and the two outside/ground rails common? And if not, how do I find where the issue might be on all of this track? Then my next question is if that is common, why did I see small sparks? I’m not an electrical engineer but somewhat capable but this one has me puzzled.

@Mellow Hudson Mike posted:

Quite simply no, never.  With nothing on the track and the transformer disconnected continuity between outside rails and the center rail is neither desirable nor tolerable in anyway.  This is by definition a short circuit.

Well, as soon as you put just one track activated accessory, like a remote switch into the layout, that theory goes out the window, as it will show continuity. It wouldn't be a "short", but would be a circuit draw from the switch to power it.

After disassembling each section of the track, one at a time to isolate each of the switches, I narrowed it down to two track powered buildings that I have.
Both of them are showing continuity across the piece of track that they were attached to - once I disconnected them the problem one away. And the continuity did not pass through the switch at each end of the run. So it was just those sections.

With a track powered accessory like a building (lights only) attached to the track, should it show Continuity? I would not think so because the ground is attached to the outside rail and the power is attached to the middle/third rail.

The switches have no effect on Continuity but those two buildings did. They are older units and they worked fine but caused the continuity. For now, I’m leaving them disconnected.
Is something shorted within the buildings?

@Raven87 posted:

I had an odd occurrence the other day. While running a train, I noticed very small sparks coming from a connection outside rail onto fast track sections. Not on the center rail, but on an outside rail. It was a short 5 inch piece that was connected to a 10 inch piece of straight fast track, but then it stopped. I checked the track (power off) with a multimeter and noticed that I have continuity between the middle/third rail and both outside rails. and with track power on I get 18 V when reading between the Middleville and either outside rail but when I check for any voltage from outside rail to the other outside rail, there’s no voltage indicated as it should be.
It only happened once (that I saw) but then I had an intermittent issue with the locomotive shutting off. I then changed both of those pieces and all seems ok.
But I still have continuity questions. My first question is, is continuity between the third/middle rail, and the two outside/ground rails common? And if not, how do I find where the issue might be on all of this track? Then my next question is if that is common, why did I see small sparks? I’m not an electrical engineer but somewhat capable but this one has me puzzled.

You're mixing different things. You have/had only 1 problem.

Bad connection between track pieces causing loco to drop out because of intermittent high resistance or loss of conductivity.

Rob answered that. You are seeing the resistance presented by the attached load, i.e., the lamp/LED in the buildings.

As there should be.

Dave

Thank you Dave. So continuity is normal when a track powered accessory is attached?
I was not aware of that but as I said, my knowledge/expertise of 3 rail electrical wiring is minimal.
Thanks again.

@Raven87 posted:

...continuity is normal when a track powered accessory is attached?
I was not aware of that but as I said, my knowledge/expertise of 3 rail electrical wiring is minimal...

Bulbs have resistance, so there will be continuity. Same thing with two-rail wiring.

Thank you Rob.

Also note, some bulbs have a low enough resistance (when cold) and multimeters a high enough threshold, that the meter will sound the continuity “beep” when used in that mode.