Re: DC Circuit Breaker?

Vollrath, Don <dvollrath@...>

Ross has a good idea. The Polyswitch type resettable fuse devices work well to protect wiring and other devices from long term overcurrent damage. For example they work great to protect twin coil switch machines from folks who like to keep the button pressed way to long. But they do not operate nearly fast enough to protect semiconductor circuits from high peak over current. However, they do have some internal (cold) resistance that tends to limit the peak short circuit current. Read the technical data sheets to find the best device p/n for your application. Several brands of competitive products exist. The DigiKey catalog (or google) is a good place to start. Having several ‘branch’ circuits each with its own Polyswitch fuse and a simple disconnecting toggle switch for servicing might be a less expensive way to go. You could put a miniature 12-14V grain-of-wheat lamp in parallel with the Polyswitch if you really want to know when/if the Polyswitch is limiting current. Be sure to mount the Polyswitch(es) in free air for best results. They do get hot when ‘tripped’.  




From: WiringForDCC@... [mailto:WiringForDCC@...]
Sent: Wednesday, November 12, 2014 8:44 AM
To: WiringForDCC@...
Subject: RE: [WiringForDCC] DC Circuit Breaker?




Our club has a similar bus.  I’ve “branched” the bus using 1 amp circuit breakers.  Each device is then connected through an appropriate  Raychem Polyswitch “resettable fuse.”  Here’s a link to the DigiKey catalog:


What accessories do you anticipate powering from this Accessory Bus?



Ross Kudlick


From: WiringForDCC@... [mailto:WiringForDCC@...]
Sent: Wednesday, November 12, 2014 1:47 AM
To: WiringForDCC@...
Subject: [WiringForDCC] DC Circuit Breaker?



Our club is rebuilding their layout for DCC. As part of the electrical, we are including a 12VDC bus to power accessorie. The bus is powered by a regulated power supply, capable of outputting 4amps. We would like to install some circuit protection, preferably an auto resetting breaker. Do any of you have a recommendation on what we should use?


Bill Hastings

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