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#37814 - 05/07/04 02:49 PM dc lamps
rmiell Offline

Registered: 11/09/00
Posts: 261
Loc: La Junta, Co. USA
This may be a dumb question, but I guess I have not thought about it before.

Can I put a regular incandescent lamp (120v, 100watts) on a 125vdc circuit?

I looked quickly through a couple of lamp catalogs, and did not find any DC rated lamps, the voltage rating were just listed as 120v, or 12v.


Rick Miell

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#37815 - 05/07/04 04:12 PM Re: dc lamps
cpalm1 Offline

Registered: 01/06/04
Posts: 62
yes, you can put a standard bulb on that circuit. however, you may wish to use "commercial" 130V bulbs rather than 120V bulbs since your circuit is 125V

#37816 - 05/07/04 09:34 PM Re: dc lamps
Bjarney Offline

Registered: 04/10/02
Posts: 2561
Loc: West-Southern Inner-Northeast ...
Incandescent lamps run fine on DC. One hitch though—most flush toggle switches are AC only. For tungsten-lamp switching, a DC {“T”} tungsten-rated switch is needed. They make plenty of racket during operation …none of that quiet AC-only stuff. They are listed as AC-DC General Use Snap Switches — UL Guide WJQR.

#37817 - 05/08/04 08:10 PM Re: dc lamps
frenchelectrican Offline


Registered: 02/06/03
Posts: 938
Loc: Wi/ Paris France { France for ...

most indscent lamps can run on dc with out any troble but bear in mind that the dc verison will run slightly dimmer but not a whole alot but bulb life will be little longer too also.. i am not sure if you know this or not when bulb fail they do flash over pretty good btw just like 277 volts ac bulbs go out simuir idea so i dont know but i will guess you allready knew this or not put a over current device there to prevent serouis arc falut.

as far for switch use the genral usage snap switch .

merci , marc

p.s. i did work on one tug boat before it ran everything on dc before so i got pretty good idea how it react with it .
Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)

#37818 - 05/09/04 01:51 AM Re: dc lamps
pauluk Offline

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
Filament lamps run on DC just fine, and if connected to a 125V DC supply you will obtain the same amount of illumination as on a 125V RMS AC supply.

Switches need to be the "quick-break" type for DC operation. The common "tumbler" switches used in this country when DC supplies were common employed a spring-action contact and opened and closed with a really noticeable clunk. The quiet AC-only switches will end up with burned contacts if used on DC.

#37819 - 05/09/04 05:37 AM Re: dc lamps
Joe Tedesco Offline

Registered: 10/07/00
Posts: 3325
Loc: Boston, Massachusetts USA
Will these switches work too?

Joe Tedesco, NEC Consultant

#37820 - 05/10/04 10:56 AM Re: dc lamps
rmiell Offline

Registered: 11/09/00
Posts: 261
Loc: La Junta, Co. USA
Ok, Thanks guys.

These lamps will be run thru a contactor, so switching will not cause a problem.

I knew you guys would give me a straight answer!!!!

Rick Miell

#37821 - 05/11/04 08:57 AM Re: dc lamps
Mean Gene Offline

Registered: 10/20/03
Posts: 137
Loc: Ohio, USA
Joe, what were you doing at my mother's house?

She still has a few of those and they work like brand new. Amazing, for being 80 years old now.


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