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 dedicated 60 amp breaker
in the home's load center, and the load is primarily resistance heating,
I think that local fusing there is redundant.

Jeff

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"As long as there are final exams, there will be prayer in public
schools"

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

Paul, KD7HB

wrote:

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

Paul, KD7HB


Got it, thanks!

I understand how a fuse works, but I'm always a little suprised when I
see just how small a cross section a fuse link has. The unblown 60 amp
links in those two Kentucky fried fuses I was ranting about measure
..008" thick by .065" wide at the narrow part. That's quite small
compared to the size of the wires needed to carry a 60 amp load.

Jeff

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"As long as there are final exams, there will be prayer in public
schools"

The sand is an essential component in current limiting fuses. It provides a
heat sink and absorbent for the metal vapor created when the fuse element
blows. Without it, the fuse barrel would be filled with ionized gases and
metallic vapor when interrupting high currents. Current interruption(if it
occurred at all) would have to wait for a natural current zero before enough
time would elapse to allow the ionization to dissipate. Conversely, current
limiting fuses have the ability to interrupt the current flow well before
the first half cycle completes. This feature much reduces total energy
released by a fault, saving equipment damage and reducing fire hazard. A
side benefit is that the fuse does not vent any hot gases into the enclosure
in which it is mounted.

Randy


wrote in message
oups.com...
Hi, Jeff.
The sand is not to quench the arc, but to hold the fusable material
steady through all those years of heating almost to the fusing point,
and then cooling. Without the sand support, the thin material would
rather quickly break.

Paul, KD7HB

R. O'Brian wrote:
The sand is an essential component in current limiting fuses. It provides a
heat sink and absorbent for the metal vapor created when the fuse element
blows. Without it, the fuse barrel would be filled with ionized gases and
metallic vapor when interrupting high currents. Current interruption(if it
occurred at all) would have to wait for a natural current zero before enough
time would elapse to allow the ionization to dissipate. Conversely, current
limiting fuses have the ability to interrupt the current flow well before
the first half cycle completes. This feature much reduces total energy
released by a fault, saving equipment damage and reducing fire hazard. A
side benefit is that the fuse does not vent any hot gases into the enclosure
in which it is mounted.

Randy


wrote in message
oups.com...

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

Paul, KD7HB


Exercising some rarely displayed diplomacy I ask, "Is it possible that
both you guys are correct about what the sand accomplishes?"

Jeff

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"As long as there are final exams, there will be prayer in public
schools"

What if I filled my renuable fuses with sand?


"R. O'Brian" wrote in message
news:7DdFd.21187$Wo.3145@lakeread08...
The sand is an essential component in current limiting fuses. It provides
a
heat sink and absorbent for the metal vapor created when the fuse element
blows. Without it, the fuse barrel would be filled with ionized gases and
metallic vapor when interrupting high currents. Current interruption(if
it
occurred at all) would have to wait for a natural current zero before
enough
time would elapse to allow the ionization to dissipate. Conversely,
current
limiting fuses have the ability to interrupt the current flow well before
the first half cycle completes. This feature much reduces total energy
released by a fault, saving equipment damage and reducing fire hazard. A
side benefit is that the fuse does not vent any hot gases into the
enclosure
in which it is mounted.

Randy


wrote in message
oups.com...
Hi, Jeff.
The sand is not to quench the arc, but to hold the fusable material
steady through all those years of heating almost to the fusing point,
and then cooling. Without the sand support, the thin material would
rather quickly break.

Paul, KD7HB

On Wed, 12 Jan 2005 18:51:06 GMT, Tom Gardner wrote:
What if I filled my renuable fuses with sand?

You'd change their characteristics in unknown ways. Why would you
do that?

Jeff Wisnia wrote:
wrote:

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


Got it, thanks!

I understand how a fuse works, but I'm always a little suprised when I
see just how small a cross section a fuse link has. The unblown 60 amp
links in those two Kentucky fried fuses I was ranting about measure
.008" thick by .065" wide at the narrow part. That's quite small
compared to the size of the wires needed to carry a 60 amp load.

Jeff

No, that's quite small when compared to the size wire to _safely_ carry
a 60 amp load.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

The least of my worries if the "Fuse Police"! Do you think I alter their
characteristics when I double-up the links?
(Actually I have fazed-out renewables in favor of 1-times due to advice I
got here and I am better for it.)


"Dave Hinz" wrote in message
...
On Wed, 12 Jan 2005 18:51:06 GMT, Tom Gardner wrote:
What if I filled my renuable fuses with sand?

You'd change their characteristics in unknown ways. Why would you
do that?

Tim Wescott wrote:
Jeff Wisnia wrote:

wrote:

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


Got it, thanks!

I understand how a fuse works, but I'm always a little suprised when I
see just how small a cross section a fuse link has. The unblown 60 amp
links in those two Kentucky fried fuses I was ranting about measure
.008" thick by .065" wide at the narrow part. That's quite small
compared to the size of the wires needed to carry a 60 amp load.

Jeff

No, that's quite small when compared to the size wire to _safely_ carry
a 60 amp load.


My, what sharp eyes you have Grandma!

Your correct of course.

Jeff (Who wonders where this thread he started is going to end up...He
sees that it's already reached the IED stage.)

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"As long as there are final exams, there will be prayer in public
schools"

On Thu, 13 Jan 2005 00:11:50 GMT, Tom Gardner wrote:
What would happen if I replaced the sand with black powder? GGG


Turns into a different kind of fuse, and makes you top-post.
Nasty stuff, that. Oh, and I think you mean FFFG.

On Wed, 12 Jan 2005 11:55:52 -0500, Jeff Wisnia
wrote:



I understand how a fuse works, but I'm always a little suprised when I
see just how small a cross section a fuse link has. The unblown 60 amp
links in those two Kentucky fried fuses I was ranting about measure
.008" thick by .065" wide at the narrow part. That's quite small
compared to the size of the wires needed to carry a 60 amp load.

Jeff
At 60 amps, your fuse is close to melting while the wire is still
safely cool.
Gerry :-)}
London, Canada

On Thu, 13 Jan 2005 00:17:17 GMT, yourname wrote:
Tom Gardner wrote:

What would happen if I replaced the sand with black powder? GGG

You'd know when the fuse blew......

You don't need to add any black powder for that - Trust me, if
there's a short on the line you'll know when it blows.

("Wow! He must have jumped 30 feet, straight up!")

A 30-amp Renewable fuse on a 480V 3Ph motor circuit makes one hell
of a BANG! blowing on a short circuit all by itself. Since there is
no sand to quench the arc, they arc over inside the body tube for
quite a while.

-- Bruce --

--
Bruce L. Bergman, Woodland Hills (Los Angeles) CA - Desktop
Electrician for Westend Electric - CA726700
5737 Kanan Rd. #359, Agoura CA 91301 (818) 889-9545
Spamtrapped address: Remove the python and the invalid, and use a net.

On Thu, 13 Jan 2005 00:10:27 GMT, Tom Gardner wrote:
The least of my worries if the "Fuse Police"! Do you think I alter their
characteristics when I double-up the links?

Ya think? And what's a fuse police? You asked 'what if', and I
responded "who knows?" with a followup of "why".

(Actually I have fazed-out renewables in favor of 1-times due to advice I
got here and I am better for it.)

Um, ok.

RoyJ wrote:

The big high voltage fuses used by the power company to disconnect
13.8KV feeder lines do have a powder charge in the base. It's needed to
blow out the plasma arc. Roughly equivilent to a 12 ga shotgun shell. I
have one that sits about 100' from my bedroom window, feeds a very old
underground line to the neighbor's place. When the cable faults late at
night in the heat of summer and the windows are open, it sure gets the
adreneline going!!!

Side note: A few weeks back, one of those fuses did NOT blow out the arc
properly. Lit up the neighborhood like a search light for 45 minutes
until the power company boys showed up to put it out. (Man, that's a job
I don't want!) Fire department showed up, parked 200' away and just
watched it.



Sort of like this?

http://home.comcast.net/~jwisnia18/temp/zap.mpg

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

Jeff

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"As long as there are final exams, there will be prayer in public
schools"

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 lines!!! I've seen that kind of switch gear, never seen it in
action. Wild!

Jeff Wisnia wrote:
RoyJ wrote:

The big high voltage fuses used by the power company to disconnect
13.8KV feeder lines do have a powder charge in the base. It's needed
to blow out the plasma arc. Roughly equivilent to a 12 ga shotgun
shell. I have one that sits about 100' from my bedroom window, feeds a
very old underground line to the neighbor's place. When the cable
faults late at night in the heat of summer and the windows are open,
it sure gets the adreneline going!!!

Side note: A few weeks back, one of those fuses did NOT blow out the
arc properly. Lit up the neighborhood like a search light for 45
minutes until the power company boys showed up to put it out. (Man,
that's a job I don't want!) Fire department showed up, parked 200'
away and just watched it.




Sort of like this?

http://home.comcast.net/~jwisnia18/temp/zap.mpg

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

Jeff

In article ,
Jeff Wisnia wrote:
:
:Sort of like this?
:
:http://home.comcast.net/~jwisnia18/temp/zap.mpg
:
: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.

--
Bob Nichols AT comcast.net I am "rnichols42"

"Robert Nichols" wrote:
Jeff Wisnia wrote:
:
:Sort of like this?
:
:http://home.comcast.net/~jwisnia18/temp/zap.mpg
:
: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.

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

RoyJ wrote:
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 lines!!! I've seen that kind of switch gear, never seen it in
action. Wild!

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

http://home.comcast.net/~jwisnia18/temp/bearclimb.wmv

Jeff

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"As long as there are final exams, there will be prayer in public
schools"