in commercial disconnects of time gone past,
it wasn't odd to see 'fuse clip clamps' adding pressure to the clip the fuse
snaps into as they would get weak with age and heat up, usually just melting
the link.
clip clamps look like little springy packman jaws with a knob that tightens
them adding additional spring pressure. imagine there's still some out
there doing their job.
"Jeff Wisnia" wrote in message
...
bumtracks wrote:
I'm just curious
.. if you know. what make and part number fuse have you been using
OK, I got your question in time to pull the remains of the fuses out of
the workshop trash can.
The fuse which opened this time, because the solder holding the fuse
link to the end cap next to the switch contacts melted, has GE's name on
it and is marked 60 AMP, One-Time Fuse, 250 VAC or less, 10,000 Amps
Internal Rating, Class H.
The other fuse in the disconnect, which fell apart when I pulled it out
because the fibre had toasted but the fuse link was still intact and
soldered to both caps, Was marked "Ace Hardware", Type NON, One-Time
Fuse, 250 Volts or less, 50,000 Amps internal rating, Class K5.
Gee, maybe now that Matt guy will come back in to tell me the problems
I've had with this disconnect were likely caused either by using an Ace
Hardware fuse in a GE fused disconnect or the fact that the pair of
fuses was "unbalanced" by 40,000 Amps. G
I am always suprised to see just how skinny fuse links actually are in
relation to the gage of the wires in the circuit they are protecting. I
just miked the link from one of those charred fuses and its only .008"
thick by .065" wide at the narrow spots. Obviously it has to be that
size to perform its function, but that small a cross section sure
doesn't "look" like it'd carry 60 amps continuously.
Sorry to waste so much bandwidth on this thread guys, it's my curious
mind always wanting to find the "real reason" why things happen.
Jeff
"Jeff Wisnia" wrote in message
...
We have a 60 amp 240 volt two pole GE fused disconnect switch in our
attic supplying the air handler/auxillary electric heat for one of our
heat pump HVAC systems. It is fed from a dedicated 60 amp breaker in the
home's load center.
That switch has been a nuisance since the house was built about 19 years
ago. Every year or so the switch contacts start heating up and will
eventually heat the end carp on one of the fuses enough to melt the
solder joining the fuse's link to the cap, shutting down things. The
overheated fuse usually falls apart when I take it out, as its fiber
tube is crisped.
I take the switch apart, clean up all the discolored switch parts with a
fine file, paint some Kopper-Shield on them and put it all back together
with a new fuse. My cleaning fixups last for another year or so and the
same contact heating thing repeats.
About six years ago I gave up and figured maybe I just had a "bad"
disconnect switch, so I bought an same model GE disconnect and just
swapped in the guts to avoid having to mess around changing the housing
and cable entries. The same switch contact heating problem happened
again a year later.
The disconnect is in a dry area, and the switch is never thrown except
when I have to fix it, so why does this happen? The current draw with
the auxiliary heaters on is less than 40 amps, and as I'm using regular
quick blow cartridge fuses, I doubt if there's much surge even when
those heaters are cold, or the fuses would blow. After a cleanup I've
let the auxiliary heaters run for ten minutes and then felt the
disconnect switch parts (with the breaker off of course). They feel like
they're only a few degrees above ambient then.
Is it just that GE fused disconnects are likely to be ****e, or am I
possibly overlooking something?
Methinks I'll just pick up a non-fused disconnect and next weekend deep
six that darned fused GE disconnect I spent an hour cleaning up this
morning, when we woke up with no heat. I can't really understand why the
installers used a fused disconnect there anyway. I appreciate the need
for a disconnect in close proximity to the equipment, but having fuses
in it when it's fed from a dedicated breaker of the same rating seems
redundant. Am I right about that?
Comments?
Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
"As long as there are final exams, there will be prayer in public
schools"
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
"As long as there are final exams, there will be prayer in public
schools"
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