Wow, Michael, look at the monster you have created, Dr.
Frankensolarbozo!
Yes, that's the thread. And I was about to post that Windy left today
for Costa Rica...just a trip, not a move.
William, there are certain perfectly appropriate applications - such as
a pressure switch controlling a DC pump, or an A/C disconnect (Square D
CU200) 2-pole array disconnect for an array-direct pump. Historically
there was nothing DC-rated available, and conservative use of available
AC equiipment worked fine and lasted forever. Sometimes it just don'
matter how it's Listed, ya just gotta use it...ya know?
Allan
Michael Welch wrote:
Is this conversation what you were refering to? 7/22/01
Others offered caution to this approach, but clearly the subject was
switches, not breakers.
Allan at Positive Energy wrote:
2. ...
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.
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.
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.
Windy
Bill Loesch wrote at 05:10 PM 5/13/2010:
Fellow Wrenches,
Some time ago, Windy Dankoff had a rule of thumb to substitute
(conservatively) an AC breaker for use in a DC application.
Is anybody's memory, or perhaps even the old dog himself; if he is
listening, better than mine?
TIA,
Bill Loesch
Solar 1 - Saint Louis Solar
314 631 1094
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