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stearman456
Joined: 14 Aug 2010
Posts: 49
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 Posted: Sat Feb 11, 2012 10:34 pm Post subject: Switch Ratings Conversion (AC to DC) for ST23N Toggle Switch |
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Hi Bob,
I just finished reading your article "Switch Ratings, What's it all
Mean?" and Chapter 11 of THE BOOK but I can't quite decipher the data
for some switches I would like to use. I have some old (but mint
condition) ST23N switches salvaged from a DC-3 audio box that was almost
certainly a 28 volt airplane. I want to use them in a 14 volt Stearman
restoration. I like them because they have a nice heavy feel, they're
made in the USA, and they're from an era when people made stuff to work
and to last. They also look nice and "period". Gleaned off the
internet I have the switche's max rating of 250 VAC, and the contact
load current rating at max rated voltage of 2.0 amps inductive AC, and
5.0 amps resistive. My running of the numbers and adding a fudge factor
into it makes me think that 30 amps inductive and 75 amps resistive at
14 volts isn't out of line. Or am I talking out of my butt?
Dan
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user9253
Joined: 28 Mar 2008
Posts: 1927
Location: Riley TWP Michigan
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| Posted: Sun Feb 12, 2012 8:58 am Post subject: Re: Switch Ratings Conversion (AC to DC) for ST23N Toggle Sw |
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Many switch manufacturers rate the ampacity of their snap action switches at 125VAC as equal to the ampacity at about 28VDC. My rule of thumb is that if a switch can carry 5 amps at 125vac, then it can also carry 5 amps at 14vdc. If a snap action switch can carry 5 amps at 250vac, then it should handle 10amps OK at 14vdc. 75 amps resistive at 14 volts IS out of line. A switch will not suddenly fail once its rating is exceeded. But the more it is overloaded, the shorter is its life expectancy. More switches fail from corrosion due to non-use than from being slightly overloaded.
Joe
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Joe Gores |
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