what amps for breakers?

Quote
phlat65
The TYCO's seem to be working fine for me, and I have driven hard on some very rough road.

On the Merkur, everything in the engine bay is handled by a seperate fuse box, utilizing blade fuses, and relays for the high current stuff.

I used the same TYCO's in Derik Nelsons M3, and he drives that car hard, still no issues with breakers tripping.

Good for you guys. 'Driving a car hard' does not equte to hitting a deep hole at the wrong angle at 60-80 mph; you know, the one that leaves you wondering for a second if the axles are still under the car. Maybe JVL's suspension is working pretty good!
These are known to have occasional issues with mechanical shocks in small aircraft and the product spec says why. It does not make sense to me to add a possible and known issue to all the things that can go wrong in a rally car, when there are ones designed for ground vehicle applications ready to go. Consider this, or ignore it, as you please; I'm just putting the info out there.

well, i already bought the breakers, so Ill put them through their paces. If it starts giving me problems, then ill look at replacing them. But i just don't have the funding to do anything about it at this point. The idaho rally should be fine with what I am for now. I also make the mistake of going a touch too far with the chassis wiring. I need to try and blend the old fuse box back in for the non essential items like brake lights, turn signals and stuff.

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First Rally: 2010 First RallyX: 2004 (a bunch)
Driver (0), Co-Driver (7)
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Last Updated, Apr 9, 2023

They'll be fine. I've used old Boeing surplus breakers since '85, no problems and I may have hit a bump or 2

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John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
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so for the headlights, which are two 55 watts, totaling like 9.1A. A 10A should give me enough room i suppose. At 14 volts (running voltage it drops to like 7.8A load). Correct?

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First Rally: 2010 First RallyX: 2004 (a bunch)
Driver (0), Co-Driver (7)
Organizer (3), Volunteer (3)
Cars Built (2.5), Engines Blown (2) Cages Built (0) # of rotations (3.5)
Last Updated, Apr 9, 2023

Quote
Gravity Fed
so for the headlights, which are two 55 watts, totaling like 9.1A. A 10A should give me enough room i suppose. At 14 volts (running voltage it drops to like 7.8A load). Correct?

Yep..

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John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

Quote
Gravity Fed
so for the headlights, which are two 55 watts, totaling like 9.1A. A 10A should give me enough room i suppose. At 14 volts (running voltage it drops to like 7.8A load). Correct?

No, sorry but wrong unless these are HID types. For Halogen or quartz or any filament type bulb, the wattage rating is only at a fixed voltage. If the voltage goes up the current WILL go up; it may not go up in proportion to the voltage as filament resistance is not constant with wattage dissapated. But total wattage will go up for anything but a HID type; those are the only constant power types around (unless maybe certain LED designs that may also have a DC-DC power converter).

So if the 55W power of the headlight is at 12V actual, then the opeating current at 14v will be higher than at 12 V. (That is why the lights gets brighter with higher voltage, BTW....!)

Also, running 9 A for any period of time through a 10A breaker is not the way to select breakers. You should run 15 or 20 A. These breakers are partly activated by heat; they are called thermal-magnetic types for good reasons. The only thing you are really able to rely upon these types to do is trip on a short or near short. Being marginally up against the amperage rating all the time, will heat the coil trip action constantly, and the hold-in action may be weakened by this heat if the actual current is always so close to the rating.

I understand you have bought these and so want to use them. No problemo. But understand that the breaker rating needs some margin above normal operating loads to avoid issues. You don't want false trips, especially on your headlights!

(And BTW, I have been doing things like fuse and breaker selection as part of my work on and off for over 30 years. I don't do it every month, but have some actual production equipment design experience in this area.)

And BTW, John, the old Boeing breakers are very likley NOT the same as the TE breakers which have been used in LIGHT aircraft like Cessnas and Pipers. These are the ones being referred to, not commercial Boeing a/c breakers. Give us a PN or series and we'll see if there is a G shock spec out there.

Basically, err on the side of caution and go with a bigger breaker if you think you're cutting it close. Just make sure the wire's gauge is up to snuff and you won't have any issues. When I do wiring in drag cars, the smallest fuse I think I've ever used it 15A. Higher current stuff like fans, pumps, etc will get 25 or 30 amps(or more if it's a killer setup).

I used to run an OEM Taurus fan on my Mustang, and that thing pulled some serious amperage on start-up...You'll hate life it you have to reset a breaker every time you turn the fan on.

Size the Wire to the Load - size the Breaker to the Wire.....

Done properly, you will never needs worry about melty-wires ruining your day (or Week!). Don't forget "headspace" to allow for load fluctuation.

Vehicle Manufacturers are quite-possibly the WORST SORRY-ASS BASTARDS for "undersizing" wiring (cheaper - lighter, quicker, dirtier) so mimicking exactly what they do is not necessarily the best practice, in every case.

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