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Is this conversation what you were refering to? 7/22/01<br><br>
Others offered caution to this approach, but clearly the subject was
switches, not breakers.<br><br>
Allan at Positive Energy wrote:<br><br>
<blockquote type=cite class=cite cite=""><font size=2>2. ...<i>
</i>I am using float switches to control 48V mercury displacement relays
for these DC pumps. Can anyone suggest a source of SPST, SPDT, and DPDT
bat (or any style) switches suitable for 48VDC nominal, low current
loads? These would be for a custom relay control enclosure with override
and remote low tank alarm signal circuits.<br>
</font> </blockquote><br>
My frequent observation on DC ratings for mechanical switch contacts is
that it's amp rating at 125VAC equals its amp rating at 28VDC. This is
consistent in the specifications of a great many switches, relays, etc.
If there are higher voltage ratings, then if voltage is doubled,
amps is half.<br><br>
When 48V is not specifically listed (nor any higher DC voltage), I feel
safe following that rule if I apply a good safety margin, as long as the
switch has a rapid snap action like a toggle switch does. For the low
current control and alarm loads you describe, I would feel forevever safe
using a switch with a 15A rating at 28VDC. If you need to get official
approval, ask the manufacturer of the switch you propose to use.<br><br>
Windy<br><br>
<br>
Bill Loesch wrote at 05:10 PM 5/13/2010:<br>
<br>
<blockquote type=cite class=cite cite=""> <br>
Fellow Wrenches,<br>
<br>
Some time ago, Windy Dankoff had a rule of thumb to substitute
(conservatively) an AC breaker for use in a DC application. <br>
<br>
Is anybody's memory, or perhaps even the old dog himself; if he is
listening, better than mine?<br>
<br>
TIA,<br>
<br>
Bill Loesch<br>
Solar 1 - Saint Louis Solar<br>
314 631 1094<br>
<br>
<br>
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