Is he confused about fuses?

[John Kogel]

I don't see a lot of fused disconnects but on Thursday I had two of them.

My client for the AM brought his electrician pal along, so i invited comments from him.

He said those are nothing special fuses, they don't have a delayed response. What is he saying? Is there a slow-blow version of these cartridge fuses?

They are 100 amp Jefferson fuses, and the house is about 100 years old.

In the PM in a 1964 house I found a Pushmatic panel powered by these Federal fuses. They are 100 amp fuses marked '80' both in pencil and with stickers. What does the 80 signify? 80%?

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[Marc]

The sparky may have been referring to super lag fuses. They don't belong in residential, only in circuits supply certain motor loads.

I don't know what the 80 means but if you ask me, fuses are far more dependable than breakers. Breakers have taken the market because they can be reset and because fuses are quite expensive when they're that big.

Marc

[Jim Katen]

Yes, there's such a thing as a 100-amp slo blo fuse.

No idea what the 80 means.

[ghentjr]

No idea about the "80" but those appear to be renewable fuses which use an internal link that can be replaced. Google renewable fuses.

[Garry Sorrells]

Motors have a high draw on start up then lower as normal run. Similar to an electric motor that is being stressed, loaded down, as it runs will increase its electrical draw. Table saw will run at 11 amps but will pull 18 to 20+ briefly at start-up. Well pumps will act in the same manor.

I know fuses as " time delay cartridge fuses" for motor circuits. The will withstand a surge as opposed to "quick acting" (typical used). Both types will be found in residential installations. Its about application.

[John Kogel]

Thanks, y'all.

"Renewable" makes sense. Those older Jefferson fuses have screws securing the caps, so they can be refurbished with a new link. They are Canadian fuses, so they got to use Robertson head screws. []

The "Renewable" lettering is too dusty to come out clear in my pics.

Jefferson Electric also made toy train transformers. I had a 'Little Jeff' transformer in my junk box for a few years, sold it at a radio swap meet.

[kurt]

Digression, but interesting observation about heads.

We used to have to import Robertson drive fasteners 25 years ago, at ridiculous expense. It's amazing to me that we had to wait 30+ years to get a decent fastener. In the US, they're still only available in some fasteners, not all. Pathetic.

[John Kogel]

Digression, but interesting observation about heads.

We used to have to import Robertson drive fasteners 25 years ago, at ridiculous expense. It's amazing to me that we had to wait 30+ years to get a decent fastener. In the US, they're still only available in some fasteners, not all. Pathetic.

Henry Ford Sr was partially to blame for the lack of Robertson head screws in the US. When Mr Robertson refused to give up his patent, Ford refused to use Robertson's screws and put a curse on him to boot. They say Mr Robertson died peniless, but the curse has affected all ye who have struggled with Phillips all these years (and now Torx, yuk).

The Robertson screwdriver is tapered so it jams in the screw head. I carry one bit that fits all the Robertson screws I normally encounter, and the one smaller size for removing receptacles. Those heads are a size smaller.

The Phillips screwdriver is there in the bag for the odd time someone subs a screw from the junk drawer.

Jefferson Electric applied for a patent of the renewable fuse design in 1927, so that dates those fuses as later additions to the house, interesting. I guess the electrician was referring to that feature and I wasn't getting it, thus there was confusion on my part. []

[Garry Sorrells]

Slo Blow Fuse ------ Time Delay Fuse ---- 100amp

FRN Series 100 Amp Fusetron Time-Delay Fuse

[Speedy Petey]

I bet someone replaced the elements in those fuses with 80A.

The 100A is the rating of the fuse cartridge itself. The element inside can be less, just like a one-time fuse.