toggle switch rating

[lucaperazzolli]

Help with my confusion !

I'm using the MIL-S-3950 (MS24523-23) toggle switch for everythings (I found a surplus stock from a friend).

I searched into Aeroelectric, forum, other source and I can't figure a clear idea about the current rating and if I'm using the right toggle switch.

Please help me to 'open my mind'.

My system is @ 12volts and I switch for :

- master master solenoid
- alt field 5a cb
- avionics master 25a cb
- landing lights 15a cb
- strobe lights 10a cb (whelen pwr pack)
- nav lights 10a cb
- interior/panel lights 1a cb (most on leds).

Here's the current rating for MIL-S-3950.

Contact Ratings (Maintained): @ 28 VDC ? 20 A (resistive), 15 A (inductive), 5 A (lamp load); @ 115 VAC ? 15 A (resistive), 10 A (inductive), 3 A (lamp load).
Contact Ratings (Momentary): @ 28 VDC ? 15 A (resistive), 10 A (inductive), 4 A (lamp load); @ 115 VAC ? 15 A (resistive), 7 A (inductive), 2 A (lamp load).

Min. 35-40 mA @ 6 VDC.

[chaskuss]

Luke,
Since your project is a 14 volt system, use the ratings listed for the 115 volt AC. These ratings are VERY close the the 14 volt ratings.
FYI, each cell in a common wet cell battery generates 2.2 volts. 6 cells multiplied by 2.2 = 13.2 volts. Add a slight (0.4 to 1.4) voltage increase to charge the battery and you see that it should be called a 14 volt system.
You should buy a copy of Bob Nuckholls excellent book on aircraft electrical systems THE AEROELECTRIC CONNECTION 12th Edition. You can order it below. It will answer nearly every question you have regarding your electrical system. See

https://matronics.com/aeroelectric/C...ECcatalog.html

Charlie Kuss

[apatti]

Charlie is right. Bob says to use the 115V ratings.

On a related note... I see you have an avionics master with a 25A CB. You are going to have trouble getting a switch for that. I have been going through this myself recently. I guess you won't be throwing the switch while simultaneously transmitting and the current draw will be a good bit less than 25A. But I don't know if it will be enough less to get you down to 15A. One thing I am considering is using both sets of contacts on double pole switch. I wouldn't double the rating of the switch if I do this though. However, I think a DP switch rated at 15A would be alright for switching 20A if you tie the contacts together.

Of course the other option is using a relay for the avionics master. This is does add another failure point, though.

Also, you may want to get some in-rush current limiters for you non-LED lamp loads (i.e. landing & taxi lights). Notice the lamp load limits on your switches are in the 2-3A range. This is because of the in-rush current.

Good luck!

[lucaperazzolli]

Originally Posted by apatti

........ On a related note... I see you have an avionics master with a 25A CB. You are going to have trouble getting a switch for that. I have been going through this myself recently.

Also, you may want to get some in-rush current limiters for you non-LED lamp loads (i.e. landing & taxi lights). Notice the lamp load limits on your switches are in the 2-3A range. This is because of the in-rush current.

Good luck!

Thanks for reply. I've just changed my 25cb into two of 15, I've cut the bus bar in two pieces.

I don't know the in-rush current limiter applications

Thanks