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Need help with fuse panel.


elwood556
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Originally posted by homnspector

Elwood556, I think what you are asking is "what is a safety fuse". An s fuse has a smaller base. There is a non-removable adapter (screws in, but not out) that should be installed in the fuse socket so you can ONLY screw in a 15 amp safety fuse for that circuit. Jim will correct me if I am wrong, but I don't think there is a safety fuse over 15 amps, as it would defeat the purpose of preventing over-fusing.

Yes i know about them and what they are. Why can't you just use a regular 15A fuse. Is it code to use a safety fuse. That's where i was getting confused. Thanks guys.

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Originally posted by elwood556

Yes i know about them and what they are. Why can't you just use a regular 15A fuse. Is it code to use a safety fuse. That's where i was getting confused. Thanks guys.

You're only supposed to put a regular edison-base fuse in there if there's no evidence of overfusing. Once someone's overfused it, you're supposed to only use S-fuses.

Reference NEC 240.51(B)

- Jim Katen, Oregon

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Hi,

I'm kind of surprised that someone didn't just say, "Get rid of the damned thing. It's an obsolete system without sufficient space in the box for decent wire bending or additional circuits and sure as the sun comes up in the morning someone's going to be tempted to over-fuse it or stick a penny in there when a fuse blows late at night when the stores are closed.

Not that fuses aren't fine - fuses are actually better than breakers - it's just that these old setups lend themselves very easily to jackleg work. Besides, they're all at least 40 years old and most electricians I know say that any electrical components over 40 years old are obsolete and need to go bye-bye.

ONE TEAM - ONE FIGHT!!!

Mike

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Originally posted by hausdok

Hi,

I'm kind of surprised that someone didn't just say, "Get rid of the damned thing. It's an obsolete system without sufficient space in the box for decent wire bending or additional circuits and sure as the sun comes up in the morning someone's going to be tempted to over-fuse it or stick a penny in there when a fuse blows late at night when the stores are closed.

Not that fuses aren't fine - fuses are actually better than breakers - it's just that these old setups lend themselves very easily to jackleg work. Besides, they're all at least 40 years old and most electricians I know say that any electrical components over 40 years old are obsolete and need to go bye-bye.

ONE TEAM - ONE FIGHT!!!

Mike

Well sure. But my impression was that Elwood started this thread as an excercise in defect recognition.

In the context of a home inspection, I'd just tell them to pitch the sucker.

Whenever you see overfusing and double taps in an old fuse box, it's a pretty good indication that the service is outdated and obsolete.

- Jim Katen, Oregon

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Just in case it's useful to anyone who isn't very familiar with these Edison-base fuses (or "screw-ins", as they're called locally):

If the fuse number starts with "W", that's an old, one-time fuse with a standard Edison base. If it's "T", that's also the standard base, but in a more modern time-delay type (not as quick to blow). If it's "S", it's a safety fuse. There may be an exception out there someplace, but as far as I know all manufacturer's of Edison-base fuses use those designations.

Brian G.

And the Penny Behind the Fuse Is Known as a "Jumper" [;)]

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Originally posted by Jim Katen

Originally posted by StevenT

If the white wire is one leg of a 240 circuit, isn't that the same as a 240 circuit in breakers not tied together?

How do you handle that in a fuse box?

You have separate fuses. Generally in the age of fuses there was no such thing as simultaneous trips.

- Jim Katen, Oregon

So isn't that a problem/defect? Since someone may not realize that a piece of equiptment is still energized, even though one leg is "blown". Kinda like Jim's humming saw and blown lights.

Additionally, the two bare copper wire that are lugged together... are they "grounds that have been energized? Or, are they insulated wires that have been stripped too far?

I know 1/4" is the amount of "casing" that should enter a panel, I don't recall how much/little insulation should be stripped at points of connections/splices.

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Originally posted by StevenT

Originally posted by Jim Katen

Originally posted by StevenT

If the white wire is one leg of a 240 circuit, isn't that the same as a 240 circuit in breakers not tied together?

How do you handle that in a fuse box?

You have separate fuses. Generally in the age of fuses there was no such thing as simultaneous trips.

- Jim Katen, Oregon

So isn't that a problem/defect? Since someone may not realize that a piece of equiptment is still energized, even though one leg is "blown". Kinda like Jim's humming saw and blown lights.

It's not really a defect; it's just the way that fuse panels worked. You can't call an older technology defective just because it doesn't behave like a newer technology. Perhaps "obsolete" or "archaic" would be better words.

Additionally, the two bare copper wire that are lugged together... are they "grounds that have been energized? Or, are they insulated wires that have been stripped too far?

Those aren't bare. They have black plastic insulation on them. You can even see the clear plastic coating bunching up slightly near where the wires are crimped. The plastic is stripped off right at the point were the wires hit the screw head.

I know 1/4" is the amount of "casing" that should enter a panel, I don't recall how much/little insulation should be stripped at points of connections/splices.

It depends on the device. Each device usually has instructions that tell you how much insulation to strip off. For most things, it's about 5/8".

- Jim Katen, Oregon

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