48V hardware [RE-wrenches]

[Kent Sheldon]

yes and no bill, switches may be operated under the peak ac voltage 
rating (125 x root2), as long as they are not used for load  breaking. 
system isolation purposes only is fine. voltage clearance is not the 
issue, current breaking with no zero crossing is. you are correct about 
the ul rating, the device must be rated for the application to realize 
the listing. and current protection devices must be listed and rated 
for any dc application.


Kent 

-----Original Message-----
From: Bill Brooks <billbrooks7 at earthlink.net>
Date: Wed, 18 Jul 2001 21:45:01 -0700
Subject: RE: 48V hardware [RE-wrenches]

> Windy,
> 
> I would be very careful suggesting any correlation of 125 VAC with DC
> there
> is no good correlation between AC and DC on switches, circuit
> breakers, or
> fuses. It must be tested and listed for DC.
> 
> Bill.
> 
> 
> -----Original Message-----
> From: Windy Dankoff, Dankoff Solar [mailto:windy at dankoffsolar.com]
> Sent: Saturday, July 14, 2001 3:51 PM
> To: RE-wrenches at topica.com
> Subject: Re: 48V hardware [RE-wrenches]
> 
> 
> 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
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