Re: Fuse for an AC motor

Homer J Simpson wrote:
"ehsjr" <ehsjr@xxxxxxxxxxxxxxxx> wrote in message news:ebgyh.7968$xu4.1923@xxxxxxxxxxx


Sure. If the resistor opens the cap, pot and opto

...

failed to energize it.

So suppose you tell us why it is a bad idea.


What happens if that motor fails? What are the safety implications? Are there fire or injury risks?


It's in the first post. If the motor draws
more current than the set point, the overload
circuit I proposed disconnects power to it, and
must be manually reset before the motor can be
started again.

Stating it for the second time: tell us why the
circuit is a bad idea. Support your contention -
maybe you have something worth discussing.


But will it continue running the motor at .37 to .45
amps, and disconnect it when current rises above
that? Nope. The CR101 is rated at 16 amps. This motor
draws .37 amps, nominal. And what happens if it fails?


You fail to understand this device. As part of the installation, a small, carefully chosen, heater element is installed which automatically opens the switch if that motor has a sustained overload.

It was spelled out in my post at 9:36 this morning.
I'll repeat it: The CR101 will *not* protect the motor.
the smallest CR101 heating element is rated at .48
amps, and requires a 125% draw to trip. The locked
rotor amps on this motor is .49 amps. The CR101 will
do nothing - it can't trip unless current drawn equals
or exceed .60 amps, and the motor draws only .49 amps
when it is jammed.
That information appears in the GE catalog on page 164 at
http://www.gecatalogs.com/content/offline/control/01_CC.pdf



16 Amps is the maximum rating only.


The same scenario as above, either the motor won't run,
or jam detection won't work. Except in your device, jam
detection won't work in the first place. So it's a
useless expenditure of money - and the expense will be
relatively huge compared to proposed circuit. Parts
for the circuit I proposed cost about $12.00, not
including the junction box, receptacle, miscellaneous
hardware.


Plus $400 or more for development and testing. Plus $1,000 to get it passed by the inspectors (assuming it ever is). Plus $200 or more for repair on each failure since no electrician will touch it.

Why are you attempting to twist the DIY project I proposed
into a commercial product? Is it because you cannot support
your contention that it is a bad idea, or are you saying
that a DIY project (not the circuit) is a bad idea for the
op when a commercial product is available?



What does the device you propose cost?


List Price: $38.00 UL/CSA listed.


That's 38 dollars, plus the electrician's fee, down
the toilet, because it cannot protect his motor.
Then you can add the cost of the replacement motor
and installation. Plus there's whatever safety
implications and fire and injury risks you had in
mind in your question, and any associated costs.
I call *that* a bad idea, and support my contention
with the information on page 164 of the url:
http://www.gecatalogs.com/content/offline/control/01_CC.pdf


The good news is that the (considerably more expensive
at $99, plus $12 for the required enclosure, plus $27 for
the heater because you have to order at least 3, plus
installation cost) CR1062R at the url you posted will
most likely do what he wants. You can get a heater for
it rated at .37 amps, so the trip current would be .4625.
That should work, except the CR1062 is designed for
infrequent starting. That may preclude it - I can't
say.

So, all that remains if for you to tell us what is bad
about the circuit I proposed. Or is your point that
he'd be better off to use the CR1062, which makes
using a DIY circuit bad in your view?

Ed






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