Today's Message Index:
----------------------
1. 09:00 AM - Re: Switch Ratings Conversion (AC to DC) for ST23N Toggle Switch (user9253)
2. 09:39 AM - Re: Switch Ratings Conversion (AC to DC) for ST23N Toggle Switches (Robert L. Nuckolls, III)
3. 11:40 AM - Re: Switch Ratings Conversion (AC to DC) for ST23N Toggle Switches (Dan Jones)
4. 01:29 PM - Impulse Coupled Mag/Elec Ignition Wiring (Jerry Jerome)
Message 1
| INDEX | Back to Main INDEX |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Switch Ratings Conversion (AC to DC) for ST23N |
Toggle Switch
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
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=366136#366136
Message 2
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Switch Ratings Conversion (AC to DC) for ST23N |
Toggle Switches
At 12:31 AM 2/12/2012, you wrote:
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?
Study the data chart more closely and keep in mind that
a switch has THREE ratings: The ability to BREAK a circuit
(which is where the high voltage ratings come from) and
the ability to MAKE a circuit (which is the largest
influence on the high current ratings. Finally, there is
the ability to CARRY a current . . . which is generally
not a published rating because it is so heavily
influenced by ambient conditions and to some extent,
installation techniques. But in any case, the CARRY
current is not less than the max MAKE current.
Emacs!
I could not find detailed data on the switch number you
quoted . . . but the data I did find gives me the impression
that these are pretty much plain vanilla, two pole toggle
switches. If you got them out of an audio box, the likelihood
that they were tasked with handling a lot of current seems
unlikely.
You would be on safe ground stressing these switches to
the lightest of the categories in the data chart
(Electrical Code Rating of 2). There are few instances
where the switch needs to be much more robust.
How would you LIKE to use them? In any case, your
assumption that the current ratings are inversely
proportional to operating voltage is flawed. There
are numerous, interleaved influences on the SERVICE
LIFE of contacts be they in switches, relays or
contactors.
Bob . . .
Message 3
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Switch Ratings Conversion (AC to DC) for ST23N |
Toggle Switches
Message 4
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Impulse Coupled Mag/Elec Ignition Wiring |
Hi Bob,
I wired the electrical system on my RV3 per Z-11 and installed the two
S-700 toggle switches for the magnetos/starter. I recently discovered that
that my engine (O-320 D2J) has two impulse coupled magnetos, not one as I
thought initially, and they are both shot so I am considering replacing one
magneto and replacing the other with a LSE Plasma III electronic ignition.
Would it be be better to replace the one mag with an impulse coupled mag
rather than go to a non-impulse coupled one? If so, how would that system
be wired? I see Figure Z-27 shows how to wire up a non-impulse coupled mag
and one electronic ignition, but does not show the wiring if that mag were
impulsed coupled. Having one IC mag would allow me the advantage of
starting the engine on that mag should I lose the electronic ignition. I
could go to a full electronic system, but feel there is an advantage to
keeping one mag because of having the different failure modes. Also, not
sure if there is any difference in how an IC mag is driven by the engine
such that it could, if desired, be replaced by a non IC mag. The mags I
have now are both Slick 4251s with left hand rotation. Thanks
Jerry
Other Matronics Email List Services
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|