Do thermal fuses fail from old age?

[Jeff Liebermann]

On Sat, 24 Mar 2012 09:24:35 -0700 (PDT), bob haller <hallerb@aol.com>
wrote:

My job involves repairing machines with thermal fuses. does anyone
make 20 amp or 30 amp rated ones?

<http://www.thermodisc.com/uploads/specs/TCO.pdf>
G8 series goes to 25A.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[jeff_wisnia]

Jeff Liebermann wrote:

On Thu, 22 Mar 2012 10:12:07 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:


Nasty cheap Chinese thermal fuses->higher rate of failure to open in a
real overtemp condition->using two in series may keep your house from
burning down, if they don't both fail the same way.


Maybe. Such guesswork would be greatly reduced if the original poster
would kindly provide the Braun model number.
https://www.google.com/search?&q=braun+coffee+maker&tbm=isch

If the coffee maker is of the drip type automatic variety, then there
are two heaters. The upper heater, that heats the water before it
goes through the coffee filter, and the warmer at the base, that keeps
the pot of coffee warm. Such a derrangement requires two thermal
fuses, one for each heater.

Incidentally, I had a really old Mr Coffee maker overheat and melt the
plastic case. The thermal fuse never blew. The consensus was that
water somehow invaded the Microtemp thermal fuse, and rusted
everything in place.

Our Bunn is a Model GRX.

The two thermal series connected fuses are both located side by side on
top of the heated water tank.

There was no accessable thermal fuse I could see located on the warmer
heater, but maybe one was buried inside it.

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10e12 furlongs per fortnight.

 

[bob haller]

My job involves repairing machines with thermal fuses. does anyone
make 20 amp or 30 amp rated ones?

the machines i repair have 15 amp thermal fuses on high inrush loads,
and the fuses fatigue fail from being close to or at their current
limit. the machines draw a instaneous 20 amps for a moment on start up

i would rather install a higher amp fuse, of the right temp, and save
tons of time and gasoline replacing the same part over and over
again.........

 

[mjb]

On 3/24/2012 7:30 AM, Stormin Mormon wrote:

Reminds me of the one time I was helping extend some HVAC duct work. The
other fellow had spent all day cutting a rectangle shaped hole in a
cinderblock wall. We came back the next day, the cable TV installer had run
a wire diagonally through our hard won duct hole. I suggested taking the
wire out with diags.

Christopher A. Young
Learn more about Jesus
www.lds.org
.

"The Daring Dufas"<the-daring-dufas@stinky.net> wrote in message
news:jkjom7$7c6$1@dont-email.me...


I was doing some control work with an engineer friend of mine I had met
when we worked on a construction project for The Star Wars "SDI" program
back in the 80's and we were installing a large HVAC control system for
a new school in the 90's and on that job, one of the young don't give a
damn electricians decided to cut and pull our control wire out of a roof
penetration conduit so he could use it. The conduit was 40' in the air
and luckily one of the other electricians told us before the ceiling was
installed. The kid's excuse for ripping out our wire was that it was in
his way and when asked why he didn't tell us so we could handle the
problem was the fact that we weren't there that day. I don't know if
personal civilian Tasers were available at the time but I would have
liked to have owned one. ^_^

TDD


TDD - Please fix your newsreader so it indents the previous poster's

contribution. It's very confusing when its all at the same indent level.

 

[Stormin Mormon]

Would it help to put two thermals, in parallel?

Christopher A. Young
Learn more about Jesus
www.lds.org
..

"bob haller" <hallerb@aol.com> wrote in message
news:09dac57f-fa1a-49b6-b21d-0d07406b105f@r27g2000vbn.googlegroups.com...
My job involves repairing machines with thermal fuses. does anyone
make 20 amp or 30 amp rated ones?

the machines i repair have 15 amp thermal fuses on high inrush loads,
and the fuses fatigue fail from being close to or at their current
limit. the machines draw a instaneous 20 amps for a moment on start up

i would rather install a higher amp fuse, of the right temp, and save
tons of time and gasoline replacing the same part over and over
again.........

 

[Jeff Liebermann]

On Sat, 24 Mar 2012 14:04:36 -0400, "Stormin Mormon"
<cayoung61***spamblock@hotmail.com> wrote:

Would it help to put two thermals, in parallel?

No. You could not guarantee that the current would split evenly
between the two thermal fuses. A more serious problem is that it
would require BOTH thermal fuses to blow in order to protect the
appliance.


--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Jeff Liebermann]

On Sat, 24 Mar 2012 13:11:45 -0400, jeff_wisnia
<jwisniaDumpThisPart@conversent.net> wrote:

Our Bunn is a Model GRX.

Thanks. Is it GRX-B, GRX-W, GRX-Basic???
<http://www.walmart.com/ip/Bunn-O-Matic-10-cup-Black-Professional-Coffee-Brewer-GRX-B/4891346>
<http://www.bunnathome.com/products/velocity-brew/velocity-brew-gr>
<http://www.bunnathome.com/sites/bunnathome.com/files/GR_use&carebooklet_english.pdf>
That style would require two thermal fuses. One on top and one on the
warmer. I couldn't find anyone selling internal repair parts that
might also have an exploded view showing the fuses.

Looks like it has a 3 year warranty. Find your receipt.
Support 1-800-352-2866. Call and ask.

The two thermal series connected fuses are both located side by side on
top of the heated water tank.

Well, that's the most likely to overheat, but it certainly would not
require two fuses to do the job. Something is wrong here.

There was no accessable thermal fuse I could see located on the warmer
heater, but maybe one was buried inside it.

Maybe, but more likely the factory forgot to install one on the
warmer. So they put it where it would fit easily, which is next to
the upper heater fuse. QA? Whazzat?

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Roy]

On 3/24/2012 1:30 PM, mjb wrote:

On 3/24/2012 7:30 AM, Stormin Mormon wrote:
Reminds me of the one time I was helping extend some HVAC duct work. The
other fellow had spent all day cutting a rectangle shaped hole in a
cinderblock wall. We came back the next day, the cable TV installer
had run
a wire diagonally through our hard won duct hole. I suggested taking the
wire out with diags.

Christopher A. Young
Learn more about Jesus
www.lds.org
.

"The Daring Dufas"<the-daring-dufas@stinky.net> wrote in message
news:jkjom7$7c6$1@dont-email.me...


I was doing some control work with an engineer friend of mine I had met
when we worked on a construction project for The Star Wars "SDI" program
back in the 80's and we were installing a large HVAC control system for
a new school in the 90's and on that job, one of the young don't give a
damn electricians decided to cut and pull our control wire out of a roof
penetration conduit so he could use it. The conduit was 40' in the air
and luckily one of the other electricians told us before the ceiling was
installed. The kid's excuse for ripping out our wire was that it was in
his way and when asked why he didn't tell us so we could handle the
problem was the fact that we weren't there that day. I don't know if
personal civilian Tasers were available at the time but I would have
liked to have owned one. ^_^

TDD


TDD - Please fix your newsreader so it indents the previous poster's
contribution. It's very confusing when its all at the same indent level.

Actually, Stormin Mormin is the one with the broken newsreader.

 

[jeff_wisnia]

Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10e12 furlongs per fortnight.

Jeff Liebermann wrote:

On Sat, 24 Mar 2012 13:11:45 -0400, jeff_wisnia
jwisniaDumpThisPart@conversent.net> wrote:


Our Bunn is a Model GRX.


Thanks. Is it GRX-B, GRX-W, GRX-Basic???
http://www.walmart.com/ip/Bunn-O-Matic-10-cup-Black-Professional-Coffee-Brewer-GRX-B/4891346
http://www.bunnathome.com/products/velocity-brew/velocity-brew-gr
http://www.bunnathome.com/sites/bunnathome.com/files/GR_use&carebooklet_english.pdf
That style would require two thermal fuses. One on top and one on the
warmer. I couldn't find anyone selling internal repair parts that
might also have an exploded view showing the fuses.

Looks like it has a 3 year warranty. Find your receipt.
Support 1-800-352-2866. Call and ask.


The two thermal series connected fuses are both located side by side on
top of the heated water tank.


Well, that's the most likely to overheat, but it certainly would not
require two fuses to do the job. Something is wrong here.


There was no accessable thermal fuse I could see located on the warmer
heater, but maybe one was buried inside it.


Maybe, but more likely the factory forgot to install one on the
warmer. So they put it where it would fit easily, which is next to
the upper heater fuse. QA? Whazzat?

I'm finding it somewhat hard to believe that the warmer heater would
overheat, since there's no thermostat in or on it which could fail in
the closed mode and cause such overheating.

I'll await comments from others regarding the need and/or usage of a
thermal fuse on the warmer.

Jeff

 

[Jeff Liebermann]

On Sat, 24 Mar 2012 08:48:09 +1100, "Phil Allison" <phil_a@tpg.com.au>
wrote:

If you run it near it's rated
maximum current (usually 5A, 15A, or 30A), it will eventually get warm
enough to melt the wax and trip the fuse.

** MASSIVE BULLSHIT !!!!!!!!!!

With a short circuit across
the power line, the self-heating will blow the thermal fuse almost
instantly.

** Nope - it will trip the supply breaker.

With a 10 times or more overload, breakers trip in a few milliseconds.

You stupid asshole.

See: UL 60691 for testing of the the thermal fuse:
<http://bbs.dianyuan.com/bbs/u/32/1122972217.pdf>
Section 10.8 discusses its use as a short circuit protection
overcurrent fuse. (This is rev 3. Rev 5 is the current version).



--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Jeff Liebermann]

On Sat, 24 Mar 2012 18:55:44 -0400, jeff_wisnia
<jwisniadumpthispart@conversent.net> wrote:

I'm finding it somewhat hard to believe that the warmer heater would
overheat, since there's no thermostat in or on it which could fail in
the closed mode and cause such overheating.

UL coffee maker standards:
<http://ulstandardsinfonet.ul.com/scopes/1082.html>
<http://bbs.dianyuan.com/bbs/u/33/1127541096.pdf>
Section 18.x for thermal cutoff requirements.
Section 23.x for whether a thermal cutoff is required.
Table 33.1 shows the maximum temperature rise allowed. As I read
between the lines, any part that might rise above the stated
temperatures, requires a thermal fuse.

UL 60691 for testing of the thermal fuse:
<http://bbs.dianyuan.com/bbs/u/32/1122972217.pdf>
Section 10.8 discusses its use as a short circuit protection fuse.

You might find this interesting:
<http://www.fixya.com/search/p89511-bunn_nhb_coffee_maker/thermal_fuse>
It's a different model Bunn coffee maker, but the problems are
probably similar.

I'll await comments from others regarding the need and/or usage of a
thermal fuse on the warmer.

Ah, truth by consensus and acclamation. Much as I like the concept,
I've seen it fail far too often.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Robert Green]

"Jeff Liberian" <jeffl@cruzio.com> wrote in message
news:ubnsm7d9jgsucm7sde447abi7r905avags@4ax.com...

On Sat, 24 Mar 2012 18:55:44 -0400, Jeff_wins
jwisniadumpthispart@conversent.net> wrote:

I'll await comments from others regarding the need and/or usage of a
thermal fuse on the warmer.

Ah, truth by consensus and acclamation. Much as I like the concept,
I've seen it fail far too often.

If I were to reassemble the device differently than the way it was designed,
I would be certain to run it in an area with nothing nearby that could catch
fire for a while to see if the consensus was correct. (-:

Protection devices are sometimes added to products when beta testing reveals
a potentially dangerous condition. Their requirement might not be obvious
by simple inspection later on.

I would only omit a fuse or protective device if it was impossible to find
an identical replacement. Even then, I would probably use the most similar
component I could find. We're talking about a device that's often operating
out a human's presence that has ignition potential. Bad kimshi.

--
Bobby G.

 

[gregz]

"Stormin Mormon" <cayoung61***spamblock@hotmail.com> wrote:

I'd like to hear. I've learned a litle about these, but I'm sure your first
hand experience will be interesting.

Christopher A. Young
Learn more about Jesus
www.lds.org
.

"The Daring Dufas" <the-daring-dufas@stinky.net> wrote in message
news:jkjom7$7c6$1@dont-email.me...

P.S. Some day I'll have to tell you of my adventures the with the Halon
fire suppression system I installed in Mission Control at the missile
range.

TDD

All I know, I got a little handheld unit. Aren't you suppose to vacate ?

Greg

 

[Stormin Mormon]

Well, Bob Haller said he had 15 amp thermals, and occasional 20 amp inrush.
Why would that need to be "current split evenly"? Supposing they are
carrying 15 amps and 5 amps. What's the problem?

If the thermals are properly placed, they would both melt open when the
device overheated.

And suppose one thermal fails from old age? Then, Bob is back where he was
when he started.

I don't see the big problem.

Christopher A. Young
Learn more about Jesus
www.lds.org
..

"Jeff Liebermann" <jeffl@cruzio.com> wrote in message
news:s86sm7t4uqtl8v4150ljpl3th24lnedo84@4ax.com...
On Sat, 24 Mar 2012 14:04:36 -0400, "Stormin Mormon"
<cayoung61***spamblock@hotmail.com> wrote:

Would it help to put two thermals, in parallel?

No. You could not guarantee that the current would split evenly
between the two thermal fuses. A more serious problem is that it
would require BOTH thermal fuses to blow in order to protect the
appliance.


--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

On Fri, 23 Mar 2012 13:27:05 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:

On Fri, 23 Mar 2012 12:48:47 -0700, "William Sommerwerck"
grizzledgeezer@comcast.net> wrote:

'Course the minuscule size of today's electronics and my aging
eyesight makes it a no-win game for me to try and do much
fixing of that kind of stuff those days.

I just bought an illuminated head-mount magnifier from Harbor Freight for
$5. It's surprisingly good. The optics have little distortion and no
chromatic aberration. There are four magnifications, but the lights "focus"
at only the lowest magnification.

I don't really like the plastic head mounted magnifiers. I'm
constantly going from whatever I'm working on, to picking up tools,
soldering iron, parts, probes, etc, on the bench. I have to keep
raising and lowering the magnifier in order to switch. With an LCD
screen, everything is roughly the same distance away, so no raising or
lowering.

If I were to buy a head mounted magnifier, it will probably be a
surgical loupe.
https://www.google.com/search?q=surgical+loupe&tbm=isch
Lots of styles and types to choose from, all seriously expensive. I've
played with some and am rather impressed. If I can keep the working
distance constant, it's as good or better than my USB camera
microscope. Mounted on eyeglasses, they are a bit heavy, but headband
mounts are available.
I use magnifiers in my work regularly and have been using a camera and

display for some of the work I do. I bought a camera and lens and
display and set it up for lathe work. But I need to get better
components because some of the details I need to see accurately are
less than .001". So even though the system I put together seemed at
first to be fine it is still has problems with contrast and
distortion. One thing that has really helped with magnifiers though is
bright lights. The really bright lighting, by causing my pupils to
constrict, gives me much more depth of field.
Eric

 

[bob haller]

On Mar 25, 7:53 am, "Stormin Mormon"
<cayoung61***spambl...@hotmail.com> wrote:

Well, Bob Haller said he had 15 amp thermals, and occasional 20 amp inrush.
Why would that need to be "current split evenly"? Supposing they are
carrying 15 amps and 5 amps. What's the problem?

If the thermals are properly placed, they would both melt open when the
device overheated.

And suppose one thermal fails from old age? Then, Bob is back where he was
when he started.

I don't see the big problem.

Christopher A. Young
Learn more about Jesus
 www.lds.org
.

"Jeff Liebermann" <je...@cruzio.com> wrote in message

news:s86sm7t4uqtl8v4150ljpl3th24lnedo84@4ax.com...
On Sat, 24 Mar 2012 14:04:36 -0400, "Stormin Mormon"

cayoung61***spambl...@hotmail.com> wrote:
Would it help to put two thermals, in parallel?

No.  You could not guarantee that the current would split evenly
between the two thermal fuses.  A more serious problem is that it
would require BOTH thermal fuses to blow in order to protect the
appliance.

--
Jeff Liebermann     je...@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

I have used thermal fuses in parell. But really dont like it as it
would cause too many problems if a fire occured.

thanks for the link for the high current thermal fuses anything that
decreases my gasoline expense is well worth it.........

 

[Jeff Liebermann]

On Sun, 25 Mar 2012 07:53:23 -0400, "Stormin Mormon"
<cayoung61***spamblock@hotmail.com> wrote:

Well, Bob Haller said he had 15 amp thermals, and occasional 20 amp inrush.
Why would that need to be "current split evenly"? Supposing they are
carrying 15 amps and 5 amps. What's the problem?

A 15A thermal fuse will not blow on a 20A inrush. It needs some time
to melt the wax inside the fuse and blow. I'm not sure how much is
required to blow it up reliably, but a short circuit across the line
should do the trick.

The problem with unequal current distribution is that the fusing
current is not predictable. However, you're partially correct. If
one fuse blows at some current, the full current load will transfer to
the other parallel fuse, which will then have enough current to blow.
The problem is that if it takes one minute for the first fuse to blow,
it will probably take more than an additional minute to blow the 2nd
fuse because of the higher series resistance which is what causes the
unequal current distribution in the first place. In effect, such a
derangement extends the time it takes for the power to be cut, and a
fire prevented.

If the thermals are properly placed, they would both melt open when the
device overheated.

That's a big if. Presumably, if the heating element was one
contiguous device, with no possibility of a partial short to the metal
water tank, there would be no thermal gradient across the water tank.
However, if the heater was a series of heating elements, distributed
in some artistic pattern across the bottom of the water tank, and only
a partial short occurs, the resulting thermal gradient will cause one
thermal fuse to be much hotter than the other, especially if the water
tank is empty.

And suppose one thermal fails from old age? Then, Bob is back where he was
when he started.

From: UL 60691 Pg 17
NOTE 2 For reasons of safety, it should be made clear in the
documentation that a THERMAL-LINK is a non-repairable item
and that, in case of replacement, an equivalent THERMAL-LINK
from the same manufacturer and having the same catalogue
reference should be used, mounted in exactly the same way.
This might explain why every pot warmer I could find has the plastic
base solvent welded shut, or metal base riveted together, to prevent
(or at least discourage) thermal fuse replacement.

However, in the case of the coffee machine, UL contradicts itself:
From: UL 1082 Pg 26
18.1 If an appliance is provided with a thermal cutoff, it
shall be secured in place and shall be so located that it will
be accessible for replacement without damaging other connections
or internal wiring. See 50.6.

So, one spec says it should be un repairable, while another says that
it should be accessible for replacement. Toss a coin.

Incidentally, if the thermal fuse blows, one should consider asking
why it blew. It isn't always old age or crappy quality. There may be
an intermittent or obscure fault causing it to blow.

I don't see the big problem.

Look harder and you'll see. What you're suggesting is not in itself
unsafe. It is possible to run parallel thermal fuses and still have
it perform its intended function. However, it's much safer to put
them in series.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Jeff Liebermann]

On Sun, 25 Mar 2012 20:24:33 -0700 (PDT), bob haller <hallerb@aol.com>
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.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[bob haller]

On Mar 25, 7:01 pm, Jeff Liebermann <je...@cruzio.com> wrote:

On Sun, 25 Mar 2012 07:53:23 -0400, "Stormin Mormon"

cayoung61***spambl...@hotmail.com> wrote:
Well, Bob Haller said he had 15 amp thermals, and occasional 20 amp inrush.
Why would that need to be "current split evenly"? Supposing they are
carrying 15 amps and 5 amps. What's the problem?

A 15A thermal fuse will not blow on a 20A inrush.  It needs some time
to melt the wax inside the fuse and blow.  I'm not sure how much is
required to blow it up reliably, but a short circuit across the line
should do the trick.

The problem with unequal current distribution is that the fusing
current is not predictable.  However, you're partially correct.  If
one fuse blows at some current, the full current load will transfer to
the other parallel fuse, which will then have enough current to blow.
The problem is that if it takes one minute for the first fuse to blow,
it will probably take more than an additional minute to blow the 2nd
fuse because of the higher series resistance which is what causes the
unequal current distribution in the first place.  In effect, such a
derangement extends the time it takes for the power to be cut, and a
fire prevented.

If the thermals are properly placed, they would both melt open when the
device overheated.

That's a big if.  Presumably, if the heating element was one
contiguous device, with no possibility of a partial short to the metal
water tank, there would be no thermal gradient across the water tank.
However, if the heater was a series of heating elements, distributed
in some artistic pattern across the bottom of the water tank, and only
a partial short occurs, the resulting thermal gradient will cause one
thermal fuse to be much hotter than the other, especially if the water
tank is empty.

And suppose one thermal fails from old age? Then, Bob is back where he was
when he started.

From: UL 60691 Pg 17
   NOTE 2 For reasons of safety, it should be made clear in the
   documentation that a THERMAL-LINK is a non-repairable item
   and that, in case of replacement, an equivalent THERMAL-LINK
   from the same manufacturer and having the same catalogue
   reference should be used, mounted in exactly the same way.
This might explain why every pot warmer I could find has the plastic
base solvent welded shut, or metal base riveted together, to prevent
(or at least discourage) thermal fuse replacement.

However, in the case of the coffee machine, UL contradicts itself:
From: UL 1082 Pg 26
   18.1 If an appliance is provided with a thermal cutoff, it
   shall be secured in place and shall be so located that it will
   be accessible for replacement without damaging other connections
   or internal wiring. See 50.6.

So, one spec says it should be un repairable, while another says that
it should be accessible for replacement.  Toss a coin.

Incidentally, if the thermal fuse blows, one should consider asking
why it blew.  It isn't always old age or crappy quality.  There may be
an intermittent or obscure fault causing it to blow.

I don't see the big problem.

Look harder and you'll see.  What you're suggesting is not in itself
unsafe.  It is possible to run parallel thermal fuses and still have
it perform its intended function.  However, it's much safer to put
them in series.

--
Jeff Liebermann     je...@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

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

 

[The Daring Dufas]

On 3/25/2012 11:08 PM, Jeff Liebermann wrote:

On Sun, 25 Mar 2012 20:24:33 -0700 (PDT), bob haller<hallerb@aol.com
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