Cigarette lighter amperage?

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JOhnH

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Is there a standard amp rating for the 12 v lighter outlet in an airplane? Will it safely provide a steady 5 amps? (I'm thinking one of those portable air conditioners). That sounds like a heavy draw.
 
JOhnH said:
Is there a standard amp rating for the 12 v lighter outlet in an airplane? Will it safely provide a steady 5 amps? (I'm thinking one of those portable air conditioners). That sounds like a heavy draw.
Click to expand...

The max continuous draw should be some fraction of the breaker protecting the circuit. I don't know a specific code or standard, but I wouldn't want to draw more than 50% of the breaker rating. For those cooler box AC units, you also have to consider inrush current to the pump on startup, some multiple of the continuous draw. That value might be labeled on the pump somewhere.
 
We had to upgrade ours so we could power ipads and such. 1977 182Q had a 2 amp circuit breaker for cig lighter and we had it changed out to a 5.
 
Be careful with this stuff, both electrically and legally. There's an AD against Cessnas regarding cigarette lighters:

http://rgl.faa.gov/Regulatory_and_G...D175D2296B42FCD686256A34006AA97C?OpenDocument

The lighter had been connected to the ammeter (basically, the bus) without any breaker whatever. Some nasty fires resulted. Breakers or fuses are there to protect the wires, and with no protection, any short will light up that wire like a filament in a bulb. It will set fire to anything around it.

Breakers are sized to the wiring connected to it, and the wiring is sized to the load. Increasing the size of breaker without also increasing the size of the wire it feeds will present a similar hazard.

Dan
 
Ok, I found out that I have a 10amp breaker, so I should be good to go.
But a 5 amp draw still seems like a lot, but I guess on a 12 v circuit it is only 60watts.
 
btw....the wiring diagrams in the maintenance manual shows the circuit, appropriate wire size, and its rating. Your A&P should have access to this....if you don't.
 
JOhnH said:
Is there a standard amp rating for the 12 v lighter outlet in an airplane? Will it safely provide a steady 5 amps? (I'm thinking one of those portable air conditioners). That sounds like a heavy draw.
Click to expand...

It depends if it was intended to take a cigarette lighter or not, old planes were made to have an electric lighter in them, and IIRC they draw between 12 & 15 amps. Just check the fuse/breaker that it is on for the value on your plane.
 
Henning said:
It depends if it was intended to take a cigarette lighter or not, old planes were made to have an electric lighter in them, and IIRC they draw between 12 & 15 amps. Just check the fuse/breaker that it is on for the value on your plane.
Click to expand...

I guess that is why Cessna's AD on the wiring says to fuse it to 10 AMPS.
 
Tom-D said:
I guess that is why Cessna's AD on the wiring says to fuse it to 10 AMPS.
Click to expand...

At 100% or even 110% load, it takes the typical thermal breaker quite a while to blow... Minutes maybe. Long enough to warm up the lighter.

They blow in a couple seconds or less into a dead short.

Cessna did kind of fuse them, though, in an odd manner... There was a thermal breaker integral to the back of the lighter socket. It would protect against an overload or short on the load connected to the lighter socket. But the wire between the bus and the lighter was unprotected, hence the AD.

Paul
 
All of the 12V outlets I've seen lately have been fused at 10A.
 
Upping a breaker without upgrading the wiring is fire waiting to happen unless the wire was oversize to begin with.
 
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