TURTLE wrote:
"zxcvbob" wrote in message
...
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.
No, the one I bought is the "pull-out" kind. I looked at the one with
the "breaker looking" switch in it and decided not to take the risk of
its switch contacts fouling up by themselves. The plug-in contacts look
pretty robust and feel tighter than a virgin's cooze. I'll swap it in
and report back in a year or two. G
I'm still scratching my head in amazement that a closed switch with what
appears to be adequate ratings located in a benign environment will
slowly develop increased contact resistance, but I've seen it and
believe it, so it must be so.
Again, my apologies for wasting all the bandwith on this simple little
problem. It's my engineer's mind dammit, I have an overwhelming desire
to learn why things like that happen, I guess it's one of my my
retirement hobbies, thoroughly non-cost effective, but fun, like many
other hobbies.
Jeff
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
This is Turtle.
Yes they do but your looking at about $68.00 + Tax . It will come with a lever
on the out side and spaded type fuses and the fuses are about $8.00 each even
being 60 amps to 100 amps sizes. The 60 amp disconnect is the breaking point
between commercial and residentiual equipment and the price reflects it. Now
this type fuse box / fused type disconnect will run at 90 amps till the cows
come home but the 60 amp cheap o will run till the sun goes down. .
The standard 60 amp fuse / disconnect $15.00 verses the 100 amp fuse box / fused
disconnect at $78.44 is a far cry between them in quality and in price. At about
5 times the cost the public will not go for 5 times the price when Home Depot
sells them for $15.00 and the home owner can replace them pretty easy.
TURTLE
--
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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