On 3/25/2012 11:08 PM, Jeff Liebermann wrote:
On Sun, 25 Mar 2012 20:24:33 -0700 (PDT), bob
wrote:

a 15 amp thermal fuse on a high inrush load causes premature failure
of the fuse, not from device malfunction but the repeated high current
rush.

this can and does cause cause the thermal fuse to fail while the
device is fine.

with gasoline so expensive i want to minimize unnecessary calls. they
annoy the customer and waste my time.//

I am ordering some high current thermal fuses in the AM

What is the device? I ask because it might be easier to install a
thermistor inrush current limiter on the input power leads, than a
bigger thermal fuse.

Inrush current limiting devices:
http://www.ametherm.com/inrush-current/
http://www.rtie.com/category-s/48.htm
According to the data sheets they have devices rated from 1 to 36
amps.


Back about 4 decades when I tried my hand at TV repair, me and the guys
I worked with had to replace a lot of what were called
"glowbars/globars", they were actually PTC devices hooked to the
degaussing coil around the CRT of a TV set to power the degaussing coil
for a short period every time a TV set was turned on. When you first
turn on a TV or CRT monitor equipped with one you may hear a "GRONK"
sound and that's the degaussing circuit. The PTC thermistor allows a big
rush of current to the coil until it heats up which causes its
resistance to increase stopping the flow of current until it cools off.
There could be a way to use a globar and one of those mil spec power
resistors in that finned aluminum case that has mounting ears and one
flat surface. The resister could be epoxied to the metal in the
appliance and hooked in series with the thermistor across the incoming
power to temper any inrush current before it hit the heating element
circuit. I see several diagrams forming in my mind's eye including one
with a low value power resister in series with the heating element
connected to the thermistor circuit and another with an NTC device in
series with the heating element and the power. The only problem would be
coming up with a thermistor that could handle the current of the heating
element when it's connected in series with it. Oh well, it's my mind,
I'll have fun playing in there. ^_^

TDD