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Only problem is it's not supposed to be coming from under the layout!  I never had any burnt wiring of any sort on the layout, but that all changed last night. I had been running maybe 10 minutes, when suddenly there was that acrid unmistakable smell of hot burning insulation. Yikes! Shut everything down really quickly and started investigating. Smoke was pretty thick under one end of the layout. Eventually I discovered the culprit: About 2 feet of burned 22 AWG wire feeding a Lionel #195 floodlight tower in my main yard. It turns out that earlier in the evening I had knocked the tower over accidentally and I guess in setting it back up one of the wires became unclipped from beneath, and quite naturally shorted to the other wire clip. Some pix below.

Here is what was left of the wire after removal:

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Here is the offending wire with arrows showing burned off insulation and peripheral damage:

IMG00399-20160716-1307

Here is the base of the floodlight tower:

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More of the wire before removal:

IMG00397-20160716-1306

One wonders how much longer it would have been before fire might have broken out? And with all that wood and homasote around, well let's just say it would not have been pretty!

Now I am typically pretty careful about circuit protection, using fuses, breakers, etc as appropriate. But here is how this came to be, and it just shows how ca-ca happens. Years ago the few accessory lighting loads on this end of the layout were served by the 10 VAC output of a Z-4000, which has a 4 amp breaker. My rational at the time was that the CB would most certainly protect the main 14 AWG circuit distributors (to strategically placed terminal strips), as well as several smaller individual 22 AWG feeders to each of several accessories. Then as time went on and more stuff got added, pretty soon the 10 VAC Z-4000 output became overloaded. So I installed a 12VAC 400 watt outdoor lighting transformer to handle all 12 VAC accessory lighting loads on the layout. The entire circuit is protected by one 15 amp fuse right at the transformer, and the whole thing has been working really well for several years. Well, had I done even a token hazop thought process I would have quickly realized that none of the small individual 22 AWG accessory feeds would be adequately protected by the main 15 amp breaker, and this whole scenario could have been avoided. When the floodlight shorted out the load quickly over-heated the wire and burned the insulation off. After repairs I measured and found that the total load on the 12VAC transformer is 8.8 amps, so I have changed the 15 amp fuse to a 10 amp. And I am installing individual 5 amp inline fuse holders on all sub section 14 AWG distribution feeds, just so this won't happen again. Live and learn I guess!

Rod

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I have become a fanatic about shutting everything off at a master kill switch at the train room's electrical source to the layout when a train is not running. Even when my attention turns to work on the scenery or anything else.
The master kill is a foot operated kill switch so all I have to do is just tap it and everything is off.

Rod's not a stranger to the hobby, so as he noted, this can happen to anyone. With those spring clip attachments, I either tin the end of the wire, or wrap it around the clip, so I've got a good connection.

Although I have all my wiring attached or bundled to wire connectors, on any accessory that can be moved (or may need to be moved for maintenance), I leave some extra loose wire beneath the train board where that accessory wiring comes through.

If something happens like what Rod mentioned, where a light tower is knocked over, with some loose extra wiring underneath, the accessory connections stay put - versus the wiring being tight and then there's no give when an accessory is knocked over or intentionally moved.

I also periodically check things, as any wire connections that aren't soldered (clips and screw connections) are more prone to coming loose with the normal vibration of trains running on the layout.

I'm sure you're thankful Rod, that as you noted, it wasn't worse than it was. A good lesson for all to take note of.

albertstrains posted:

 Larger wires say # 18 would have tripped overloads and not acted like a soldering gun tip lol. Small wire sizes are fine but you should fuse them at a lower ampacity rating

Al

Sage advice Al, and a rule that I rigorously follow. But on this occasion I out-foxed myself by switching my original power supply without considering the small feeders connected to this area of the layout.

"The sad thing about experience is that you often don't have it until just after you needed it"

Rod

For those of us who use postwar transformers to power accessories, let this be a warning to use external fuses or breakers.  I don't know of any transformers that have small enough breakers to protect against an overheating 22-gauge.  This example also indicates another reason for using "oversize" wire:  it allows sufficient amperage to flow to pop a breaker or fuse.

Be aware that several old Lionel transformers have no overload protection whatsoever on certain post combinations.  The old type R is an example.  I have breakers on the accessory outputs of the ZWs I use for accessories,  lighting, & powering switches.

cjack posted:

I wonder if a smoke/gas vapor detector under the layout would sense the hot wire faster...might be worth having anyway.

I just stopped by Menards and picked up 2 ionization and photo cell type detectors for $17 each...and 11% off

It's important to get the ionization feature for non smoke vapors.

Last edited by cjack

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