Electrical: Bussman fuse letter codes

[Ron Dame]

I found out that my overdrive was not working because of a fuse I had added. It was a 10A AGC. 10 amps is fine, but as far as I can recall, and AGC is not a slow-blow, which can take spikes. But I don't know, I've never known what teh letter stand for, and I have close to 25 packs of various glass fuses of different ampereages and these letter codes.
I've had limited luck on googling for these ancient ( I assume) codes, and am wondering if anyone has a cheat sheet on what these letter codes mean

[Skip Lackie]

AGC indicates a physical size , not an amperage. They come in various amperages. If you have to squeeze one end of the holder to get it to latch, you have the right size, but maybe not the right amperage.

[Ron Dame]

Thanks Skip, I'm not surprised about physical size, but what about slow-blow vs fast(?) blow? Are there any other things to consider?

[ronstrasser]

Ron
All the following are Buss Fuse designations. Other fuse manufactures have their own designation for their equal fuses
AGC is a normal blow glass 1/4 inch round fuse. About 1 1/4 inches long
ABC is a normal blow ceramic Fuse also 1/4 by 1 1/4 inches
MDL is a Time Delay fuse 1/4 inch round and 1 1/4 inches long
MDA is a slow blow equal to the MDL
SFE is the type of fuse that was use in Studebakers. They were designed for automotive use. They are 1/4 inch round and various length depending upon amperage.
Neither AGC or MDL fuses were ever used in Autos as far as I know.

Example A SFE 20 is about 1 1/4 inch long a SFE 14 is about 1 1/16 long
Ron

[Ron Dame]

That's what I wanted to know. Since the fuse that I added to my overdrive somehow blew over winter, I wondered if it was because it was not a slow-blow fuse. Everything else checked out fine, no shorts or anything. And it is fine once again, so I'll stick with it. Thanks!

[Skip Lackie]

Years ago, I bought some 1930s- 1950s Buss Fuse displays, complete with fuses (the kind that every gas station used to have on a shelf), and a couple of Buss fuse catalogs. At the time, I was utterly confused by the different numbers on what appeared to be identical fuses. I happily lived in ignorance and just replaced fuses with identical ones until this thread has prompted me to actually study the matter a bit. As noted above, ACG is/was a fuse size, about 1.25 inches long. I have them in many amperages. Before WWII, the ACG size was called 3AG -- I've got lots of them, too. There were/are smaller sizes, too. 1AG (about 3/8" long) became AGA; 7AG (7/8" long) became AGW; 8AG (1" long) became AGX; 9AG (1 7/16" long) became AGY, etc.

Around 1959, the new SFE system came into use. I'm still confused on the degree to which SFE and AGC fuses are interchangeable --except that Buss says that they are NOT. The SFE fuses seem to get longer as their amperage increases.

[Ron Dame]

Years ago, I bought some 1930s- 1950s Buss Fuse displays, complete with fuses (the kind that every gas station used to have on a shelf), and a couple of Buss fuse catalogs. At the time, I was utterly confused by the different numbers on what appeared to be identical fuses. I happily lived in ignorance and just replaced fuses with identical ones until this thread has prompted me to actually study the matter a bit. As noted above, ACG is/was a fuse size, about 1.25 inches long. I have them in many amperages. Before WWII, the ACG size was called 3AG -- I've got lots of them, too. There were/are smaller sizes, too. 1AG (about 3/8" long) became AGA; 7AG (7/8" long) became AGW; 8AG (1" long) became AGX; 9AG (1 7/16" long) became AGY, etc.

Around 1959, the new SFE system came into use. I'm still confused on the degree to which SFE and AGC fuses are interchangeable --except that Buss says that they are NOT. The SFE fuses seem to get longer as their amperage increases.

That's my issue too. If it fits and the amps are correct, I've been plugging them in, and I have quite a few. and a couple of boxes are C(XX), some are G(XX) Are some slow-blow? Or are there other differences? Eaton/Bussman haven't been really helpful.

[StudeRich]

All you have to do is check the Shop Manual or the Owner's Guide for the correct Fuses, the Overdrive takes a SFE14, it has too much Load for a 10 AMP.

[Ron Dame]

All you have to do is check the Shop Manual or the Owner's Guide for the correct Fuses, the Overdrive takes a SFE14, it has too much Load for a 10 AMP.

Well, I added the fuse, because there was none ('63 Champ) maybe that's why the 10A blew, though it worked for over 15 years! Still, what are the C and G prefixes about?

[ronstrasser]

Ron;
Bussman is now owned by Eaton. Businessman's catalogue's are available online. Other manufactures of 1/4 inch fuses include Little Fuse, Chase Shawmut, Edison and others. You can also Goggle a particular fuse number along with the fuse manufactures. And usually it will include a graph with the blow caricaturist verses time of the fuse in question.
Ron

[Lark Hunter]

* SFE--- Society of Fuse Engineers (not kidding )
* AG--- Automotive Glass. These ones all have a 32 volt maximum, and come in many flavors. I believe the third letter denotes the physical dimensions of the fuse.
* The MDL, MDQ, denotes that the fuse is a slow blow, time delay, or in some way modified from a regular old fuse. You can generally identify these by their non-standard internals; often there's a spring, what looks like a blob of lead, etc. in place of or combined with the standard fuse element. I'm not sure if these types are found in automotive applications.

From there, it splinters off in so many different directions that your head will spin... since tubular glass fuses were and still are used in household and professional electronics, there are a bunch more types tailored to those applications. The ceramic or cartridge style fuses are often filled with sand or some other inert material to quench arcs from clearing a very high overcurrent fault.