DC rated rocker switches?

[Glenn Ashmore]

I think I know the answer to this but I would like some other opinions:

I am trying to select some sealed DC rated miniature rocker switches to
be used as manual overrides for a remote digital DC lighting system.
Real estate on a boat electrical panel is limited so the circuit is SMT
and designed to be very small. Size of the switches is important. DC
switching is harder on the contacts than AC because of arcing but these
switches will be used only to operate navigation lights should the
digital system fail so they will cycle much less than 30-40 times a
year. Maximum load on any circuit will be about 4 amps with a maximum
inrush load of possibly 8 amps.

It seems that only one in ten miniature rockers is DC rated and those
that are are 3 to 4 times as expensive. Almost all DC rated rockers are
"standard" size. Evidently to give the contacts more thermal mass.

In the course of my search I was surprised to find that the rockers on
Cessna, Beachcraft and many other light aircraft are not DC rated. The
reasoning being that a typical landing light switch might be operated at
most 2-3,000 times over 10 years so derating a 25,000 cycle AC rated
switch by 90% is acceptable to the FAA.

So, unless someone comes up with a good reason not to, I am going to use
15A@120VAC switches.

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

 

[Mark Fergerson]

I think I know the answer to this but I would like some other opinions:

I am trying to select some sealed DC rated miniature rocker switches to
be used as manual overrides for a remote digital DC lighting system.
Real estate on a boat electrical panel is limited so the circuit is SMT
and designed to be very small. Size of the switches is important. DC
switching is harder on the contacts than AC because of arcing but these
switches will be used only to operate navigation lights should the
digital system fail so they will cycle much less than 30-40 times a
year. Maximum load on any circuit will be about 4 amps with a maximum
inrush load of possibly 8 amps.

It seems that only one in ten miniature rockers is DC rated and those
that are are 3 to 4 times as expensive. Almost all DC rated rockers are
"standard" size. Evidently to give the contacts more thermal mass.

In the course of my search I was surprised to find that the rockers on
Cessna, Beachcraft and many other light aircraft are not DC rated. The
reasoning being that a typical landing light switch might be operated at
most 2-3,000 times over 10 years so derating a 25,000 cycle AC rated
switch by 90% is acceptable to the FAA.

So, unless someone comes up with a good reason not to, I am going to use
15A@120VAC switches.

Have you looked at automotive parts? They may not be
labeled as waterproof, but I've never seen one with water in
it (ask me about the rare, but enthusiastic thunderstorms
and the time my driver's-side window gasket failed).

If panel space is that tight, how about an add-on panel
with the "right" parts??

Mark L. Fergerson