switch current limits

[bobmarkert]

I have convinced myself that a 20 amp switch mean it can withstand 20 amps flow during the on-off cycle. Once contact is made can a 20 amp switch pass through more than 20 amps? What's driving this question is my desire to use a switch, without a relay, to power/de-power my avionics buss. The current is less than 20 amps when turning the switched ON, but once ON the the transponder and VHF radio may occasionally take the load above 20 amps during simultaneous transmissions. Will this be a problem as long as the load is less than 20 amps during the switching cycle?
Thank You

[airguy]

Yes, that is going to be a problem. Put in dual switches and split the avionics bus. This might be a good time to make them basically redundant (comm1 on one bus, comm2 on the other, etc) so that if you lose one bus you don't lose all functionality.

[bobmarkert]

Originally Posted by airguy

Yes, that is going to be a problem. Put in dual switches and split the avionics bus. This might be a good time to make them basically redundant (comm1 on one bus, comm2 on the other, etc) so that if you lose one bus you don't lose all functionality.

Ok so that got me thinking,..... Will a DPST 20 amp switch handle 20 amps per pole (side?) for a total of 40amps? If anyone can point me to basic "switch 101" class I'll gladly do the research

[az_gila]

Yes, wire two poles in parallel.

It might not make 40 amps but it will be better than one pole.


Check that the 20 amp rating you are using is a 12 V DC rating.

[bird]

I would like to add a reminder also that switches are rated in ac and dc currents, please make sure you buy a switch, for your airplane, that is rated in dc amperes.
The difference is very important. Happy building.

Bird

[6 Gun]

Thats a lot of amps for two radios and a transponder what are you using.
Bob

[bobmarkert]

Originally Posted by 6 Gun

Thats a lot of amps for two radios and a transponder what are you using.
Bob

2 x G3X screens
GMC305 AP controller
Dual ADAHARS
Dual magnetometer's
Dual TCW backup battery
GTN 650
PAR 100EX
GDL 39
GTX 23 ES transponder
proton torpedo generator

i have yet to do the math with a sharp pencil but the GTN Comm and GTX23 in reply mode eats up some amps. there is another thread running right now about an EFIS switch which has me considering moving the screens to the main buss

[Jeff A]

Originally Posted by bobmarkert

2 x G3X screens
GMC305 AP controller
Dual ADAHARS
Dual magnetometer's
Dual TCW backup battery
GTN 650
PAR 100EX
GDL 39
GTX 23 ES transponder
proton torpedo generator

A VP-X would complement all that awesome equipment very nicely. Use any switch you'd like to turn equipment on/off.

They don't pay me, I'm just a big fan.

[bobmarkert]

thanks Jeff,
I thought long and hard about VP-X and decided against it, so that decision is behind me and in my mind irrevociable. I know the cost will be similar for VP-X and traditional CB's. I'm starting to pull wires for a conventianal electrical system.

[Neal@F14]

Personally, I'd put the EFIS/EMS/ADAHARS/etc on an "instruments" breaker and switch circuit that is separate from the radios/xponder breaker and switch. Having it all on one single "avionics" switched circuit is putting a lot of eggs into one basket. Just my personal opinion anyway.