TURTLE wrote:
"Jeff Wisnia" wrote in message
...

TURTLE wrote:


"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"


This is Turtle

Jeff , These fuse disconnects are stated as rated at 60 amps but if you read
the amp draw rating in the data plate with it. You will see it is suppose to
be used on amp draws of less than 40 amps.

It states that it will handle short time useage of near 60 amps but when put
in a contenous amp draw the 40 amps your drawing on it become the max it will
handle. I have the Connecuit Electric type I use on condenser outside and
they are rated at 60 amps but if you read closely you will see it says
contenous use 40 amps is the MAX. it will handle. You just don't run anything
at Max. By running this disconnect at 40 amps is like it says on the Lexus
LS-400 Maxium operating speed is 161 M.P.H. and then you can run it at that
speed and be safe. So if you don't run your car at Max. Speed 160 M.P.H ,
Don't run your 60 Amp disconnect Rated at Max. Amps 40 Amps.

Well now, I'll check the specs and if that's the case it sure makes sense now!
And too bad the original installer didn't see it that way too, it would have
saved me a lot of nuisance fixups.

Thanks, and I hope the 60 amp Aquare-D non-fused plug type disconnect switch I
just bough yesterday isnn's similarly rated. G

Jeff




This is Turtle.

No that Square - D breaker looking disconnect is rated above the 40 amps but
usely in about 2 to 4 years the breaker will burn inside the breaker and go out
and then you can replace it with a real breaker square- D and keep going. A lot
of HVAC people don't like them for that call back coming in 2 to 4 years. Now if
you replace it now with a real breaker to apply to the application you will not
see it down the road.

TURTLE




Do they make a 100A disconnect that just has a pull-out block with 2
cartridge fuses in it? That's what I think I would use if they are
available that big. Put in whatever size fuses you actually need to
protect the heater, (45A?) or just put 100A fuses in it and let the
breaker back in the main panel provide the protection.

Bob