Circuit breakers

[daveymc29]

I'm no electrician so this has me stumped. I have the, looks like a brown square bakelight, circuit breaker with the silver rivet on one end and copper on the other holding the round pieces, that fit into the fuse holder, onto the bakeliight. I hadn't noticed the difference in the rivets until they were pointed out on this site with the precaution that there is a forward and a backward way to install them. Sure enough I tried and if I mount it one way I can detect a spark as it settles into the fuse holder. If I install it the other way around I don't see the spark. I installed one so I don't see the spark and will check it tomorrow to see if the battery has lost charge. I had no idea these things were directional. Are the fuses also? I have had dead batteries with both fuses and circuit breakers, but much more so with fuses. How do it know, is there a thermos in there? Must be to know the difference from hot and cold. (We had that discussion in a firehouse determining that the smartest invention of man was the thermos, it knew to keep hot, hot, and cold, cold.) Serious stuff we used to discuss around the dinner table. Any comments will be welcome. The circuit breakers I use are 30 Amp, 12 volt, placed into the starter located fuse holders on a 12V, Neg grd car and also on a 6V, Pos. Grd car.

[Synchro909]

Dave, I don't bother with a circuit breaker, I just carry a few spare fuses. If I blow one or two, I repair them at a little higher ratring. Been doing it for decades.

[eagle]

They use two different types of metal with different temperature characteristics. As the current flows through them to a certain level, they don't heat enough to move but eventually as the current increases, the bimetal actuator heats up and bends, separating the contacts. When the contacts are separated the current stops flowing, allowing the bimetal to cool, thus returning to its original shape, closing the contacts. Rinse, repeat... These type of circuit breakers are suseptible to high ambient temperatures, and do deteriorate with continued over-current. Pros: automatically reset, slow blow Cons: they get weak with use, affected by ambient temps, not as accurate or as fast as a fuse

[WHN]

Stick with fuses. They won’t automatically reset.

Also fuses can be put in either way. Enjoy.

[rotorwrench]

Shortstop circuit breakers use studs as terminals. The use of the term rivet is confusing. They have the copper terminal so that a person can tell which side that is directly connected to the fixed end of the bi-metallic strip inside. Many have "bat" molded in the plastic next to that copper terminal to indicate that it is the buss power in side. The tin coated silver terminal connects to the accessory to be powered and that is the side that is connected directly to the bi-metallic strip.

They will work either way but they will act faster as a breaker when properly connected. An aircraft manual reset type circuit breaker would be another choice to use rather than a fuse. With a fuse, you have to carry spares. In any case, if it opens the circuit protector then it indicates a short or high resistance that needs to be corrected before restoring power to the circuit.

Here is a you tube. https://www.youtube.com/watch?v=vA1cz021OvU

[Badpuppy]

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Breakers and fuses are nonpolar. They won't by themselves cause the battery to drain. A current of only a few amps will drain a battery in a short time, so a 30A breaker won't prevent that. Note that just leaving a dome or dash lamp on overnight will do a job on the battery. You need to find the cause of the current draw - you may have a pinched/frayed (yellow) battery wire or possibly a cutout, horn, or lighting switch on its way south.

And always check your ammeter for discharge after you shut off the engine.

[Mike V. Florida]

Some of them are marked as to the supply and the accessory. On the ones that are marked, the copper end goes to the positive of the battery and the chrome goes to the negative. Now depending on how your car is set up depends on the direction in the holder.

Some like them and as you can read some don't. I for one use them as does most of the members of our club. To each their own.

[rotorwrench]

With respect, the ground has nothing to do with circuit protection other than it being a source for short circuits when there is damage or deterioration to the conductor in the circuit. The copper terminal is always connected to the buss side of the battery whether it is positive or negative. The non buss side of the battery is ground whether positive or negative. I only bring this up due to confusion between positive or negative ground.

A circuit protective device protects the wire conductor of the whole circuit all the way from the fuse or breaker to the accessory that draws the current to function. If the wire conductor shorts to ground, the whole circuit will get hot until it is opened by the protector regardless of where the short in the circuit is located. Wires burn fast too if unprotected.

[katy]

I have the, looks like a brown square bakelight, circuit breaker with the silver rivet on one end and copper on the other holding the round pieces, that fit into the fuse holder, onto the bakeliight.

Got a picture? So I can understand what you're talking about.

[The Master Cylinder]

Originally Posted by katy

Got a picture? So I can understand what you're talking about.

Like this. This is the kind I use. They don't reset until the problem is corrected when installed correctly. Fits in the fuse holder sold by the vendors.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[rotorwrench]

It's definitely not a short stop type.

The thing shouldn't spark at all when being pushed into fuse holder clips. If it does spark then some circuit is powered up or it has a short somewhere. Something is completing a circuit to ground in the system. That is the only way it can spark. Later model cars have clocks that are hot all the time but I can't think of any other circuits that would be operational all the time for a model A.

[LEM]

All the information I could find on these circuit breakers told me that they are for up to 12 V, so are these OK to use in a 6 V system?

[rotorwrench]

First off, they are amperage sensitive. Most modern automobiles are 12-volt so they have to mention that they are low voltage rated for the average automotive application. Any low voltage system can use them including 6-volt. The system voltage will have no affect on the amperage they are rated for unless a person tried to use them for higher voltages like 60-volts or more. A person can weld with higher DC voltages.

[katy]

The information for the CB says: "Opens automatically on overload. Remains open for protection until trouble is corrected."

I understand that they reset when power is restored to the circuit, so they must have something inside that requires a bit of power to do the resetting. This is possibly where the small spark comes from when re-installing them.

Do they reset if installed wrong polarity?

[Badpuppy]

Originally Posted by LEM

All the information I could find on these circuit breakers told me that they are for up to 12 V, so are these OK to use in a 6 V system?

The Bussman/Cooper/Eaton CBF breakers are Type II which stay open after trip, until power is removed. The latching circuit is designed for 12V, and may not operate at 6V. If not, it will simply act as a standard type I and cycle on and off, perhaps much more rapidly than the usual thermal type, which will give less protection.

I'd stick with the glass tube fuse, or wire in a thermal breaker. They operate reliably at any voltage that doesn't arc through the insulation.

[Badpuppy]

Originally Posted by katy

The information for the CB says: "Opens automatically on overload. Remains open for protection until trouble is corrected."

I understand that they reset when power is restored to the circuit, so they must have something inside that requires a bit of power to do the resetting. This is possibly where the small spark comes from when re-installing them.

Do they reset if installed wrong polarity?

It's the latch that requires a tiny amount of power, through the overload. The latch is released when power is removed.

I've never seen a circuit interrupter that requires a polarity.

[rotorwrench]

The CBF type breakers are type II. They just reset on their own after power is taken away from the circuit. These don't cycle like a type I breaker but they work the same way. They use a resistor connected internally to hold the breaker open. It would be important to have these connected correctly or they might not reset. Here is a Data Sheet for Littlefuse. https://www.littelfuse.com/~/media/a...t_breakers.pdf


A good 30-amp resetable Klixon breaker is more expensive but at least it can be manually reset after it pops. I've used short stop type breakers for years on Harley Davidson motorcycles and for lighting in big trucks and they are reliable enough. Ford used them for a long time in both cars and trucks. They are easy to wire in too. I just use a piece of thick copper buss bar connected to the power source and then attach the breaker by the copper stud to hold it in place. You can then attach the buss feed wire to the silver terminal. The only bad thing is that you have to to isolate each circuit one by one to find a short.

[Mike V. Florida]

Maybe these will help a little,
As you can see some are marked with polarity and the other shows how it works, small wire heats up, bi-metal springs open and since the current can only go through the small wire it stays hot until the voltage it removed and the bi-metal cools off.

[30 Closed Cab PU]

So if the small wire is taking the short, max amps, why doesn't the small wire blow?

[eagle]

It's a heat coil only. Only heats when bimetal contactor is open, produces enough heat to keep the bimetal hot. When load is removed, no current and no heat, bimetal closes and off to the races you go.