One of the major advantages of the bulb over the circuit breaker is that the 
bulb will allow other locomotives in the same power district to continue to 
operate during the short.

Chris Borgmeyer

Re: DC Power supply  (use automotive bulbs as fuses)
Posted by: "dhultay" [email protected]   dhultay
Tue Nov 29, 2011 10:48 am (PST)

Bill,
Sorry to take so long to reply, was enjoying the Thanksgiving weekend.

Responses regarding "current limiters" are correct, an automotive bulb will 
glow brightly below facia with a medium current draw (2.5amps) on power 
district. 
However, they will burn-out when a larger amount is drawn from power supply 
(i.e. sustained dead short) preventing melted plastic trucks with derailments.
It can get costly to replace automotive bulbs if you have alot of derailments 
/dead shorts.
Advantage over $30 electronic circuit breakers for each power district is they 
tolerate transient shorts better, allowing trains (and other power districts) 
to continue to operate when only minor rough spots are encountered.

On the mighty Pennsy with a busy mainline running multiple head end power, a 10 
amp power supply should last longer than a 5 amp supply. If you are drawing 3 
amps for one A/B/A unit, you will be operating at 60% rating of 5 amp power 
supply, but only 30% of 10 amp supply. When another consist closely follows 
A/B/A unit, you may be maxing out 5 amp supply.

Same can be said for decoders. If A/B/A unit has three 1amp decoders, just need 
to spend time programming via handheld controller for MU lash-up. However, if 
you wire one decoder for A/B/A unit, would be better to use MRC 3amp decoder.

Once you start running layout, you will be the best judge on how to adjust 
power districts, circuit breakers and decoders. However, don't feel like you 
have to add alot of extra $30 electronic circuit breakers, when a $2 automotive 
bulb may do the trick. Regards,

Dennis H.
Soon to be in Saratoga NY


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