Re: DCC Wiring - Can it cause a fire?

Vollrath, Don <dvollrath@...>
 

Poor connections, too small a wire to support an overload and outright arcing that causes excess heat while limiting current to less than the protective fuse or CB trip point is what allows most electrical fires to get started. Houses, industry, model RRs… makes no difference.

So, Yes, there is a potential of starting a fire. As others have pointed out 5 amps x 16 volts (actually more like 12-14) under the right/wrong conditions can cause 60-80 watts of pure heat, somewhere on your layout. But there are three possible conditions here, neither of which will be positively prevented by circuit breakers. 1) If the malfunction current path includes a relatively high resistance (something greater than about 2.75 ohms), call it a partial short if you wish, that causes less than the full 5 amps to flow, a full 60-80 watts may be concentrated at that location causing lots of heat. Since current is limited to be less than the circuit breaker trip point, it will never trip or automatically shut down. A short circuit between two power pick-up trucks connected together with small gage wire can rapidly get hot enough to melt plastic. A poor solder joint track or puny feeders may provide the current limiting resistance. 2) If the mentioned malfunction causes sparking and current is somehow being limited by undersized wiring, the sparking arc itself can be hot enough to start paper, plastic and wood on fire. (think welding) 3) Notice that even with current limiting light bulbs, a good solid short at the load end will cause the bulb to light up quite brightly and the glass surface can soon become hot enough to burn fingers or start a paper fire.

 

However, if you have followed the principles of wiring for DCC… a) You will use robust wiring with plenty of track droppers and verify that a short anywhere on the track will cause the circuit to become interrupted by the booster protective device or electronic CB. b) Always follow the manufacturer’s recommendations when it comes to selecting, using or connecting a power supply for/to a booster or other accessory. AND c) Never leave the DCC system turned on while totally unattended, with or without locos running. Pay attention… Stuff happens.

 

DonV

 

From: WiringForDCC@... [mailto:WiringForDCC@...] On Behalf Of Robmorrison@...
Sent: Saturday, January 18, 2014 1:33 PM
To: WiringForDCC@...
Subject: [WiringForDCC] DCC Wiring - Can it cause a fire?

 



A friend told me that he knew of a situation where a DCC system left on heated up the wires, especially the track feeders, so that a fire started all along under the track. He said the fire official told them that it looked like the fire was started and spread along the line of the track. He then went on to say that at 5 amps and 16 volts, we have about 80 watts going, quite a bit more than the average soldering iron, hence the fire potential. It is not known if there were separate circuit breakers.

 

I am a bit skeptical, but wondered if anyone on this list knows about this possibility.

 

My own On30 layout, which is only 12-feet by 12-feet, is separated into four districts, each protected by a DCC Specialties circuit breaker.  Probably overkill, but I feel better about it that way.

 

I would think that the circuit breakers would handle all or most shorts.  But what could be the cause of drawing enough power to heat things up that much without triggering any overload protection?  Unless the power station portion of the DCC system' s overload protection failed, I cannot envision the above problem.

 

Thnaks for any insights you may have.

 

Rob Morrison




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