Anyone knows where I can buy this type of fuse (Glass)? It’s the same size as the original fuse. Thanks. Image Unavailable, Please Login
Hi Mike, any markings on the end caps ? That doesn’t look like a 12v fuse more likely a mains power AC fuse Sent from my iPhone using FerrariChat
According to the rating those eBay fuses are 8A at 32V. That makes them equivalent to a 22A fuse in a 12V circuit. So if the circuit calls for a 22A fuse, they're OK but if it calls for less, then that fuse will not protect the wiring.
Do your research. The rating on the fuse is the voltage rating and has no effect on the opening current rating of the fuse. The voltage rating always has to be greater than the circuit being protected. I am an instrumentation / electronics instructor. You never install a fuse with a voltage rating less than the circuit. Even the original exposed fuse element GBC-8 has the same ratings as the glass type. Image Unavailable, Please Login Image Unavailable, Please Login
Yes per above. Look at any AGC fuse, they say on the fuse end its rated for 250V, and used in a 12V passenger car. Doug
"Do your research. The rating on the fuse is the voltage rating and has no effect on the opening current rating of the fuse." Thank you for the info...As an electronics instructor perhaps you can straighten me out... I have done a lot of work on marine systems that use 24v and 32V as well as 12V DC systems. The fuse used for the same components on a 12 V system typically are 2x the rating of the fuse used on a 24 or 32V system. The wiring is also a couple of gauges larger on the 12 V system running the same components. For example, a 12V bilge pump may need a 10A fuse while a 24/32V bilge pump of the same power (wattage) uses a 5A fuse. Using 10 Amps as an example because it's easy: 10 amps at 12 volts is 120 Watts 10 A at 24 volts is 240 Watts 10A at 250 V is 2,500 Watts Since Watts is the actual power being "transmitted" to do the work - the same fuse cannot provide the proper protection for the wiring at all those voltages. If it could, a 20 amp glass fuse in a car could be used in the 20 amp circuit in my house. So...what am I missing?
Forget about Watts for the moment. When the fuse blows, there is potential for arc. This potential is greater with higher voltage. Therefore, a fuse rated for 12v will not offer the desired arc protection in a 240v circuit. Also, you're perhaps forgetting that AC and DC circuits behave differently - and fuse designs are different for each as well.
Wire sizing is based on wattage of all the loads on the individual circuit. Wiring sizing determines the max current which it can provide safely. (Overheating the wire) Something to look at: https://storage.heightslibrary.org/materials/hrrc/15-Electrical_Repairs/GENERAL_ELECTRICAL/FUSE-WIRE_RATINGS.pdf
Yes, I'm well aware of ampacity - I used those tables extensively in wiring new marine circuits. I also know that the system fuse is to protect the wiring, NOT any individual components attached to it - which may or may not have their own fuses. IOW, we want the fuse to blow before a short circuit overheats the wires and starts a fire. So...I'm back to my original question - if a fuse is rated for 10A in a 32VDC circuit, isn't it the equivalent of a 22 Amp fuse if placed in a 12V circuit? If you put 250V through that 10A Bussman fuse with a variable resistor on the other end to represent a load, and slowly increase the power draw, does anyone believe it could accept 2500 Watts - more than enough to spin the starter motor? The amperage of a fuse (or breaker) has to be specified to operate in the specific amp/volt combination that the circuit uses to deliver power.
You're not accounting for base resistance in the circuit. In your 32v example, the base resistance is 3.2Ω - which is high for a circuit with no active load; in your 12v, it's .5Ω.
Well, OK! I apologize for hijacking the thread! Apparently I don't understand electrical circuits as well as I thought I did. Clearly I need to do some studying/research. If I wasn't on a break from remodeling a bathroom I'd start that research now but it will have to wait till this eve! Hopefully I'll be smarter tomorrow!
Admittedly, this probably belongs in the "who cares?" category. If you need a 10 amp fuse, you go buy a 10 amp fuse, you don't need to know the history of fuses and how they actually function. If you are of that view, no need to read further! However... I did a LOT of reading and these are probably the two docs were the most informative to me: https://www.allaboutcircuits.com/technical-articles/understanding-the-details-of-fuse-operation-and-implementation/ https://www.littelfuse.com/~/media/electronics/application_guides/littelfuse_fuseology_application_guide.pdf.pdf This was my epiphany moment (It appears others here knew/realized this but I didn't): Fuses operate based on voltage drop! Therefore, the amp rating of a fuse is independent of the systems circuit voltage. I use voltage drop testing a LOT in marine and auto circuit testing but it never occurred to me that that's technically what causes a fuse to blow. But as soon as it's pointed out, it's one of those, "DUH! Well, of course!" moments. The voltage drop increases the current which creates the heat that blows the fuse/pops the breaker. So: 1. As Thorn pointed out, the voltage rating of a fuse has nothing to do with its normal operation, only its 'blown" operation to avoid arcing. Just like a capacitor, you can always use a fuse that exceeds the circuit's nominal voltage but you can't use one that is lower. (I replace lots of capacitors - one of my main side-jobs is restoring vintage tube/valve audio gear). 2. As far as a fuse is concerned, amps is amps. The amps that the fuse is concerned with are generated by the voltage drop across the fuse, NOT by the nominal voltage in the circuit. IOW, if all is well, there is no voltage drop across the fuse. 3. I never really thought about temperature and fuses but there can be quite noticeable differences in fuse operation based on ambient temperature since fuses are rated at 25C. Above that they can withstand less current; below that they can withstand more. Ambient temp is NOT air temp; it is the temp where the fuse is located which might be much warmer than air temp.
Sort of related: I've heard the following statement since I was a teen, "It's not voltage that kills you, it's amps." While technically true, it is also very misleading when trying to understand the fundamentals of electrical circuits; one might assume something like "Thousands of volts are safe, I guess. So there's no difference in 10,000v vs 12v." And there most certainly is, of course. A similar (but misleading) statement would be, "It's not speed that kills you, it's impact." Well... yes, the impact is what shatters your skull. But the force of the impact is a direct result of the speed (and mass, sure) you were traveling before you hit the brick wall. Just like speed/impact, volts and amps are related. The voltage is how much potential the source has (in effect) to deliver amperage across the circuit - or any medium - including air.
