Chinese Fuses - Danger Will Robinson

When the grand-kids come over, 10 and 7, I like to take them into the shop and do experiments. It's fun for me and maybe educational for them. I had recently mounted a combination amp and voltage gauge. We talked about volts and amps, then for some hands on I decided to show how fuses protect the circuit. I demonstrated this by shorting out a fine strand of wire which got red hot, smelled terrible and ultimately flamed off the insulation. We would need a fuse to prevent that fire.

I had them fashion a short circuit with a fuse to protect the wiring. They watched the fuse pop when the circuit was energized. We blew several fuses so each of them could look closely at the glint as the fuse blew to prevent damage to the wiring. We had one inconsistent result during the process where a fuse refused to blow so I quickly switched off the circuit before my wiring heated up to the point of melting the insulation. We continued the excitement, blowing many more fuses.

A couple days later, I thought about that one fuse that refused to immediately blow. It was a slightly different hue, though similar in color than the rest of the fuses we had tried. I looked around my collection for other fuses with the same appearance. Yup, there was a small bag of them that came with a fuse block I had installed on the boat. I decided to put them to the test by rigging them in a short circuit. I watched the gauge as I switched on the power. 

My 12 volt lawn mower battery fed the circuit. Here's what I saw when I switched on the power. The volts would drop to less than 5 and the amperage got over 66.

 

Here are the results:

The 5 and 10 amp fuses did blow, but not until plastic case melted. I cut the power on the 20 and 30 amp fuses before they blew because my wiring got too hot. I wiggled the 5 and 10 amp fuses out of the holder before they cooled off. I waited until the 20 and 30 were cool before removing them.

So folks, it's a good idea to use only name brand high quality fuses.