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.

From A 1975 Dairy Queen House Rag

 

We did end up buying a 27' sailboat. We lived aboard for about 3 years sailing from New England to the Caribbean.

New Tech For Old Boat

Big Duck is a 1972 Land-n-Sea houseboat. I've owned her for a little over 10 years.

Here's the story on Big Duck
 

The last time out with the family, the macerator wouldn't work. I had run clean water into the black tank and wanted to pump it out. The macerator pump wouldn't come on. It can get stuck after not being used for a time, so I thought it just needed a manual nudge with a screwdriver -- but that didn't get it going. It had to be the fuse. If I ran the macerator for too long, sometimes it would blow the fuse. I'd stopped most of that problem by putting a 5 minute timer in the circuit, but even then if it had to work real hard sometimes the fuse would pop.

Sure enough, when we returned home I could see the fuse had blown. The fuse panel is in the bilge and is not easy to see or access. This panel runs circuits in the bilge that are independent of the helm, like the macerator, bilge lights and bilge spotlight, two separate bilge pump circuits (with different buzzers for each so I can tell from the helm when they come on), a relay for the electric fuel pump and hookup posts to conveniently hook up the timing light (rather than having to get to a battery).

Not only being tough to see, it's a rats-nest of wires which yes, I'll get around to sanitizing one day. Then while changing the macerator fuse I noticed my secondary bilge pump came on. That pump is only supposed to run if the bilge water overpowers the primary pump. The fuse for the primary bilge pump was good, so I assumed the primary bilge pump or switch had failed. 

I ordered and installed a new bilge pump switch. I like these because there' no moving parts.

After installing the new primary pump switch, the primary bilge pump still wouldn't come on. It wasn't the pump because I could jump it to get it running. Figuring I'd screwed up the installation or had a defective switch, I pulled the switch back out and tested it on the bench. It worked fine. I totally rewired the primary pump to be sure the wiring wasn't the culprit. The damn pump still wouldn't come on. 

Then guess what? I discovered the fuse was blown. After all that work, I'd probably blown that fuse either taking the old switch out or putting the new one in. What a waste of time!

 Deciding I was never going to go through that again I decided to modernize the fuse panel. Today's fuse panels come with little led indicators that light up when the fuse has blown.

 I got the new panel here.

So now, I can easily tell when a fuse is blown without standing on my head and squinting. 

This is a bad macerator fuse - as witnessed by the red led.

And while I was at it. I decided to install a meter for testing 12 volt stuff. Testing that new bilge pump switch and future testing was made easier by incorporating a new volt and ammeter circuit on my workbench

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