Amp ratings for AC switches

jakerock · Post by **jakerock** » Mon Oct 13, 2008 10:51 am

The on / off switch on my recording interface (Presonus Firepod) stopped working and I have been trying to find a replacement.

The original one (PRONIC T85?), that is broken is a simple switch (2 connections=SPST?) I assume that it simply breaks the connection between the two wires... Its rated at 5A / 250VAC or 10A / 125VAC

When I look at my options at radio shack, choosing by the Amp rating, I have only a few choices, and they are very bulky and seem alot more "heavy duty" than the one I am replacing, also requiring that I drill a larger hole in the sheetmetal of the unit to install.

I think it is this one:
http://www.radioshack.com/product/index ... age=search

There are much more elegant switches available at R.Shack that are old school cool toggle style, and would fit the existing hole in the sheet metal, but they are rated @ 3A / 125VAC or thereabouts.

The wires leading to the switch are no bigger than 22 gauge, so I am wondering if replacing with a 3A rated switch is really an issue at all...

Any thoughts?
Thanks alot
-Jake

Nate Dort · Post by **Nate Dort** » Mon Oct 13, 2008 11:14 am

Put a meter between the two wires and see how much current it is drawing. That should tell you if 3A will be enough.

jakerock · Post by **jakerock** » Mon Oct 13, 2008 11:23 am

Thanks for being kind to the noob nate!

{EDIT} OK I am REALLY a NOOB.

I set the meter to 150ACV and bridged the wires that connect to the switch...
Got a reading of 100V
Then I googled, learning that the formula for determining amps is:
Amps = Watts / Volts

I apologize in advance, but how do I determine the watts to make this calculation?

Thanks very much!

Best, Jake

Nate Dort · Post by **Nate Dort** » Mon Oct 13, 2008 11:31 am

Wait, there's an easier way to figure this out. I just checked this page:
http://www.presonus.com/products/Detail ... roductId=3

It says:

Power Requirements (Continuous) 20W

20W @ 120VAC is 167mA, so a 3A switch should be plenty. There's probably some momentary startup current that goes higher than 167mA, but I still think a 3A switch should handle it.

jakerock · Post by **jakerock** » Mon Oct 13, 2008 11:49 am

Oh OK!!!!
Thanks alot for your help Nate...

Fantastic.

So, I guess this also answers my question above about determining watts...
One way is to RTFM!!!! Jesus.

Thanks again, jake

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Amp ratings for AC switches

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