Can someone confirm what the "sand" in typical cartridge fuses is put there for? I suspect it probably has to do with quenching a high current arc before it eats everything up. I'm looking at a 60 amp 250 vac fuse right now which is labled "Class K5, 50,000 amps internal rating" and which spilled sand on me when it crumbled apart yesterday as I was pulling it out of its holder.If arc extinguishing is what the sand is there for, is maybe a chemical reaction involved?My focus on fuses right now is because I've been living at home for the past 19 years with a 60 amp GE fused disconnect which has a proclivity for having its contacts start heating up after about a year or two of service protecting the circuit to a HVAC heat pump air handler with auxillary resistance make up heaters in it.The stationary switch contacts are just the flat sides of the fuse clips on the input end of the fuses. (The other side of those clips are curved to match the fuse end caps.) So, when the contacts start oxidizing, they eventually get hot enough to melt the solder joining the fuse link to the inside of the fuse end cap, the circuit opens, and the air handler quits.Along the lines of "Things which go away by themselves usually come back by themselves.", if I disassemble the switch parts and dress all the contacting parts clean, then apply a little Kopper-Shield to them, the darn thing works like a charm for so long that I forget about it until we wake up to "no heat" on a cold morning and I have to climb into the attic to fix it. I even went as far as to buy a new set of GE guts for the thing about 8 years ago, thinking maybe the original installer had just gotten a dud. but the same thing happened a year or so later.Yesterday I went out and bought a Square-D non-fused disconnect to replace that GE fused disconnect. It looks like it's got much "tighter" contacts in it.I understand the safety importance of having a disconnect next to the equipment, but as the circuit is protected by a...

Hi, Jeff.The sand is not to quench the arc, but to hold the fusable materialsteady through all those years of heating almost to the fusing point,and then cooling. Without the sand support, the thin material wouldrather quickly break. Paul, KD7HB

OT- What's this sand in cartridge fuses?

Jan 12, 2005 23 Replies

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RoyJ 21 years ago

Good grief NO!!!!! I was talking about the puny 13.8 KV that will merely fry a tree that leans against the wire. That clip was some of the

100++ KV l> RoyJ wrote:

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Robert Nichols 21 years ago

In article , Jeff Wisnia wrote: : :Sort of like this? : :

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:I don't know if the clip is real or fake, but it is impressive. : :Jeff

It's real. It's from SWEPCO in Shreveport, LA with the explanation:

"This is a 3 phase 500KV motor operated disconnect that is NOT intended to be opened under load. There is a switcher that is designed to open under load in the circuit that is supposed to open load and then the disconnect opens. In this case, one phase of the switcher failed to open, resulting in one phase of the disconnect opening under load. The resulting arc was truly spectacular. The reason that this event was caught on camera is because this particular switcher has had a failure to open in the past so every time the switcher was opened, a camera has been set up. This time they got the failure on tape"

The arc sustained until an upstream circuit breaker stopped the current.

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Jon Danniken 21 years ago

Bert Hickman has a few other "arcs and sparks" up on his page here, for those who are into this sort of thing: http://205.243.100.155/frames/longarc.htm Jon

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Jeff Wisnia 21 years ago

Oh, then it must have been more like this one. One tough and lucky bear:

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Jeff

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