Do thermal fuses fail from old age?

[Phil Hobbs]

N_Cook wrote:

Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote in message
news:4F6B3337.79C9D482@electrooptical.net...
The Daring Dufas wrote:

On 3/21/2012 11:03 PM, jeff_wisnia wrote:
Over the years I've had a few thermal fuses in houshold appliances go
open for no apparent reason. When I've replaced them with ones with
the
same temperature rating they stayed working fine for years more.

A couple of days ago our three year old Bunn coffee maker quit,
because
a 141 degree celcius overtemperature thermal fuse on the water tank
opened. It might possibly have happened because the water tank
thermostat stuck closed, but after I repaired it the thermostat cycled
just as it should.

I was suprised to find that there were TWO identical thermal fuses
connected in series located right next to each other, the bodies were
actually touching. That seemed like a belt and suspenders approach,
unless there's a significant likelihood that a thermal fuse won't open
when it should?

Comments?

Thanks guys,

Jeff



I could understand parallel fuses because one may not handle the
current. Perhaps in series it's safer because the unit will shut
off if one fails to open?

TDD

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.

Perhaps the voltage rating was lower than the required use, ie in fused
state not rated for the service voltage across the broken section so someone
thought, I know , we'll put 2 in series ;-)

Nah, even good equipment is made that way. I sort of collect
European-made espresso machines, and they all have two thermal fuses in
series with the thermostat. (I don't collect the fancy ones, you
understand--I just took a fancy to the long-discontinued Krups Il Primo,
because it has the best designed valve in the business. I've bought
about 5 off eBay at various times.)

Cheers

Phil Hobbs

 

[Phil Hobbs]

jeff_wisnia wrote:

N_Cook wrote:

jeff_wisnia <jwisniadumpthis@conversent.net> wrote in message
news:Su6dnWicsZ8DOffSnZ2dnUVZ_gmdnZ2d@giganews.com...

Over the years I've had a few thermal fuses in houshold appliances go
open for no apparent reason. When I've replaced them with ones with the
same temperature rating they stayed working fine for years more.

A couple of days ago our three year old Bunn coffee maker quit, because
a 141 degree celcius overtemperature thermal fuse on the water tank
opened. It might possibly have happened because the water tank
thermostat stuck closed, but after I repaired it the thermostat cycled
just as it should.

I was suprised to find that there were TWO identical thermal fuses
connected in series located right next to each other, the bodies were
actually touching. That seemed like a belt and suspenders approach,
unless there's a significant likelihood that a thermal fuse won't open
when it should?

Comments?

Thanks guys,

Jeff


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



The larger resettable switch type are usually rated as combined
(self-heating) current and thermal cutout. Maybe similar for "Woods" metal
types , say if in circuit with fast switching on and off thermostat or poor
contacts , so repeated inrush curent combined with a standing temperature.



The thermal fuse in our Bunn coffeemaker was marked as being made by
MicroTemp, labled series G7.

Just for Ss & Gs I looked them up today and learned that there's more
inside them than just a "fuse link" that melts at the trip temperature.

There's quite a bit of stuff in that little sucker.

Look here:

http://tinyurl.com/786eslm

Works just like the little plastic things that come in Thanksgiving
turkeys.

Cheers

Phil Hobbs

 

[Jim Yanik]

"Gareth Magennis" <sound.service@btconnect.com> wrote in
news:L6SdnfoCxPZWmPbSnZ2dnUVZ7sOdnZ2d@bt.com:

"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:9svnffFicfU1@mid.individual.net...

"Tony Hwang"

I understand they work on bi-metal strips.


** Nope - that is a temperature switch.

Thermal fuses like this one use the melting point of some material
and rely on a spring to open the circuit.

http://media.digikey.com/photos/Cantherm%20Photos/SDJ1%20DF100S.jpg



.... Phil



This is the type Peavey have hidden in the mains transformer of the
Classic 30.
I only discovered it by accident when I decided to dissect an "open
circuit" one, no mention in the schematics AFAIK.

The owner had had 2 mains transformers replaced previously, seems,
from Googling, these transformers are woefully underpowered and often
break. Wonder if the only failing part is actually this switch?


Gareth.

see if you can get to the thermal fuse and replace it with something rated
better,or just bypass it for test,using an external fuse.

ISTR reading in SER about others who eliminated the thermal fuse and
successfully reused transformers.


Also,consider how instrument amps are often used.(misused?)



--
Jim Yanik
jyanik
at
localnet
dot com

 

[Jeff Liebermann]

On Thu, 22 Mar 2012 00:03:41 -0400, jeff_wisnia
<jwisniadumpthis@conversent.net> wrote:

Over the years I've had a few thermal fuses in houshold appliances go
open for no apparent reason. When I've replaced them with ones with the
same temperature rating they stayed working fine for years more.

A couple of days ago our three year old Bunn coffee maker quit, because
a 141 degree celcius overtemperature thermal fuse on the water tank
opened. It might possibly have happened because the water tank
thermostat stuck closed, but after I repaired it the thermostat cycled
just as it should.

Yep. See UL CHAT (conductive heat aging).
<http://www.intercontrol.de/00_img/pdf/article_TH100_en.pdf>
UL tests for thermal cutoff problems in appliances. The logic is that
if the thermal fuse is going to fail, it should always fail in the
direction of safety. So, if the cutoff threshold drifts, it should
always drift toward opening early. The same logic applies to thermal
type electrical circuit breakers, which are designed to lower the
threshold value after being tripped a few times.

I was suprised to find that there were TWO identical thermal fuses
connected in series located right next to each other, the bodies were
actually touching. That seemed like a belt and suspenders approach,
unless there's a significant likelihood that a thermal fuse won't open
when it should?

The coffee distillery is double insulated, which means it doesn't need
a ground pin on the power plug. Since a fault can affect either side
of the power line in such a symmertical arrangement, two fuses are
required. Note that the thermal fuses also act as an internal short
protector. I doubt if the fuse died from CHAT. My guess is it had an
internal fault, probably from internal water accumulation during
washing, which blew the fuse.

Jeff

Yet another Jeff.


--
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 00:03:41 -0400, jeff_wisnia
jwisniadumpthis@conversent.net> wrote:


Over the years I've had a few thermal fuses in houshold appliances go
open for no apparent reason. When I've replaced them with ones with the
same temperature rating they stayed working fine for years more.

A couple of days ago our three year old Bunn coffee maker quit, because
a 141 degree celcius overtemperature thermal fuse on the water tank
opened. It might possibly have happened because the water tank
thermostat stuck closed, but after I repaired it the thermostat cycled
just as it should.


Yep. See UL CHAT (conductive heat aging).
http://www.intercontrol.de/00_img/pdf/article_TH100_en.pdf
UL tests for thermal cutoff problems in appliances. The logic is that
if the thermal fuse is going to fail, it should always fail in the
direction of safety. So, if the cutoff threshold drifts, it should
always drift toward opening early. The same logic applies to thermal
type electrical circuit breakers, which are designed to lower the
threshold value after being tripped a few times.


I was suprised to find that there were TWO identical thermal fuses
connected in series located right next to each other, the bodies were
actually touching. That seemed like a belt and suspenders approach,
unless there's a significant likelihood that a thermal fuse won't open
when it should?


The coffee distillery is double insulated, which means it doesn't need
a ground pin on the power plug. Since a fault can affect either side
of the power line in such a symmertical arrangement, two fuses are
required. Note that the thermal fuses also act as an internal short
protector. I doubt if the fuse died from CHAT. My guess is it had an
internal fault, probably from internal water accumulation during
washing, which blew the fuse.


Jeff


Yet another Jeff.

In response:

The Bunn coffee maker we have uses a 3 pin grounding cord and plug.

The two thermal fuses were definitely in series with each other in the
hot side of the line feeding the thermostat controlling the storage tank
water temperature, and the also feeding the switch which controls the
"keep warm" heater under the carafe.

I think we've about "saucered and blowed" this subjuct by now, thanks all.

Jeff

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

 

[Jules Richardson]

On Thu, 22 Mar 2012 05:53:14 -0700, trader4@optonline.net wrote:

I would suspect that part of the problem today is a lot of the thermal
fuses are being made in places like China with poor quality control.

I would suspect that part of the problem today is a lot of the thermal
fuses are being made in places like China, who will build to whatever
level of quality they're told to build to, and unfortunately there aren't
many of us who want to pay an extra ten cents for our product to ensure
that the fuses don't fail prematurely. ;-)

cheers

Jules

 

[Jules Richardson]

On Thu, 22 Mar 2012 11:25:06 -0400, Phil Hobbs wrote:

Look here:

http://tinyurl.com/786eslm

Works just like the little plastic things that come in Thanksgiving
turkeys.

What, the bag of guts?

 

[Geoffrey S. Mendelson]

Jules Richardson wrote:

I would suspect that part of the problem today is a lot of the thermal
fuses are being made in places like China, who will build to whatever
level of quality they're told to build to, and unfortunately there aren't
many of us who want to pay an extra ten cents for our product to ensure
that the fuses don't fail prematurely. ;-)

Not only that but the vendors at your end don't want them to last anyway.
Except for consumer electronics, people don't get rid of old items and buy
new ones because they are obsolete with enough frequency to keep them
in business.

They really do make it in volume, and not on single sales.

So if your coffee maker did not die after a year or two you would probably
be using it for the next 20 years.

The latest innovation in coffee makers is the cartridge ones, where the
profit is in the single use cartridges that you must buy.

I am packing up for a crosstown move, after 16 years in this apartment, and
I a finding kitchen items that I had when I moved in, some of which are still
in use everyday. Some I have had that are still in use, but not daily, since
the 1970's, but they are not electric.

Geoff.

--
Geoffrey S. Mendelson, N3OWJ/4X1GM
My high blood pressure medicine reduces my midichlorian count. :-(

 

[jeff_wisnia]

Geoffrey S. Mendelson wrote:

Jules Richardson wrote:


I would suspect that part of the problem today is a lot of the thermal
fuses are being made in places like China, who will build to whatever
level of quality they're told to build to, and unfortunately there aren't
many of us who want to pay an extra ten cents for our product to ensure
that the fuses don't fail prematurely. ;-)


Not only that but the vendors at your end don't want them to last anyway.
Except for consumer electronics, people don't get rid of old items and buy
new ones because they are obsolete with enough frequency to keep them
in business.

They really do make it in volume, and not on single sales.

So if your coffee maker did not die after a year or two you would probably
be using it for the next 20 years.

The latest innovation in coffee makers is the cartridge ones, where the
profit is in the single use cartridges that you must buy.

I am packing up for a crosstown move, after 16 years in this apartment, and
I a finding kitchen items that I had when I moved in, some of which are still
in use everyday. Some I have had that are still in use, but not daily, since
the 1970's, but they are not electric.

Geoff.

It gives me great joy to beat the manufacturers at that game Goeff.

Instead of spending about an hour driving to and from a Walmart to buy a
new Bunn Coffeemaker for $99.00 (plus 6.25% sales tax) I spent less than
a dollar on a thermal fuse and maybe half an hour in my workshop fixing
it while SWMBO cooked up a batch of eggplant melanzano (yummy) for
dinner. (She loves to cook and I love to fix busted things others have
to toss out.)

'Course the current miniscule size of todays 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. 'Twas much easier in the vacuum tube era of my
youth 65 years or so ago when I occasionally even ecountered those old
fashioned resistors which were just round sticks of carbon composition
with right angle solid wire leads wrapped around each end, then painted
and color coded with paint dots.

Jeff

PS: Do you find folks screw around with the second "e" in your first
name by leaving it out or moving it ahead of the "r"?

My first name has only one "e" in it, but unless it goes from my
keyboard to an address or salutation without ever encountering a human
the odds are many to 1 that some jerk will assume I don't know how to
spell my own name and stick an extra "e" in it for me.

The spelling of my name isn't that unusual:

Google Hits on:

Jeffry 9.3 million

Jeffery 48.8 million

Jeffrey 264.0 million

But yours is the winner...

Geoffrey 86.2 million

Geoffry 0.812 million

Geoffery 1.8 million



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

 

[gregz]

micky <NONONOmisc07@bigfoot.com> wrote:

On Thu, 22 Mar 2012 00:03:41 -0400, jeff_wisnia
jwisniadumpthis@conversent.net> wrote:

Over the years I've had a few thermal fuses in houshold appliances go
open for no apparent reason. When I've replaced them with ones with the
same temperature rating they stayed working fine for years more.

A couple of days ago our three year old Bunn coffee maker quit, because
a 141 degree celcius overtemperature thermal fuse on the water tank
opened. It might possibly have happened because the water tank
thermostat stuck closed, but after I repaired it the thermostat cycled
just as it should.

I was suprised to find that there were TWO identical thermal fuses
connected in series located right next to each other, the bodies were
actually touching. That seemed like a belt and suspenders approach,
unless there's a significant likelihood that a thermal fuse won't open
when it should?

I wouldn't think they fail just from age, but what do I know?

I r eally posted to ask how you crimp them in place, what kind of
connector do you use?

And where do you buy them?

Comments?

May it be our biggest problem.

Thanks guys,

Jeff

I solder them back in. With heat sinks of course. I used to buy them from
mcm. I had different temps in my storage.

 

[Phil Allison]

"Jeff Liebermann"

The coffee distillery is double insulated, which means it doesn't need
a ground pin on the power plug. Since a fault can affect either side
of the power line in such a symmertical arrangement, two fuses are
required.

** Horse manure.

One fuse is sufficient to break the circuit in case of current overload.

Note that the thermal fuses also act as an internal short
protector.

** Even worse horse manure.

Thermal fuses act on temperature, not current at all.

The max current rating given by makers is based on self heating to ensure
the fuse stays within temp rating tolerance.



..... Phil

 

[Michael A. Terrell]

N_Cook wrote:

Perhaps the voltage rating was lower than the required use, ie in fused
state not rated for the service voltage across the broken section so someone
thought, I know , we'll put 2 in series ;-)

Which would do nothing, if they couldnn't handle the voltage.

Have you ever looked at the wiring in a furnace? They use multple
thermal shutdowns, for liability in the US.


--
You can't have a sense of humor, if you have no sense.

 

[N_Cook]

Michael A. Terrell <mike.terrell@earthlink.net> wrote in message
news:OeGdncrMOvJ61_HSnZ2dnUVZ_iydnZ2d@earthlink.com...

N_Cook wrote:

Perhaps the voltage rating was lower than the required use, ie in fused
state not rated for the service voltage across the broken section so
someone
thought, I know , we'll put 2 in series ;-)


Which would do nothing, if they couldnn't handle the voltage.

Have you ever looked at the wiring in a furnace? They use multple
thermal shutdowns, for liability in the US.


--
You can't have a sense of humor, if you have no sense.

so you have no visual sense for emoticons

 

[The Daring Dufas]

On 3/23/2012 5:44 AM, N_Cook wrote:

Michael A. Terrell<mike.terrell@earthlink.net> wrote in message
news:OeGdncrMOvJ61_HSnZ2dnUVZ_iydnZ2d@earthlink.com...

N_Cook wrote:

Perhaps the voltage rating was lower than the required use, ie in fused
state not rated for the service voltage across the broken section so
someone
thought, I know , we'll put 2 in series ;-)


Which would do nothing, if they couldnn't handle the voltage.

Have you ever looked at the wiring in a furnace? They use multple
thermal shutdowns, for liability in the US.


--
You can't have a sense of humor, if you have no sense.


so you have no visual sense for emoticons

It's known as H.I.S.I., pronounced "hissy", it describes the disease
Humor Irony Sarcasm Impairment. People with that particular mental
disease are said to have H.I.S.I. fits and often put on a big display of
pseudo-intellectualism about the subject at hand when they fail to see
the humor or bizarreness of statements made by someone who is attempting
to pull their leg. It's also called The Mr. Data response
in some circles. ^_^

P.S. They often get mad when someone like me is teasing them.

TDD

 

[N_Cook]

The Daring Dufas <the-daring-dufas@stinky.net> wrote in message
news:jkhorv$6ho$1@dont-email.me...

On 3/23/2012 5:44 AM, N_Cook wrote:
Michael A. Terrell<mike.terrell@earthlink.net> wrote in message
news:OeGdncrMOvJ61_HSnZ2dnUVZ_iydnZ2d@earthlink.com...

N_Cook wrote:

Perhaps the voltage rating was lower than the required use, ie in
fused
state not rated for the service voltage across the broken section so
someone
thought, I know , we'll put 2 in series ;-)


Which would do nothing, if they couldnn't handle the voltage.

Have you ever looked at the wiring in a furnace? They use multple
thermal shutdowns, for liability in the US.


--
You can't have a sense of humor, if you have no sense.


so you have no visual sense for emoticons



It's known as H.I.S.I., pronounced "hissy", it describes the disease
Humor Irony Sarcasm Impairment. People with that particular mental
disease are said to have H.I.S.I. fits and often put on a big display of
pseudo-intellectualism about the subject at hand when they fail to see
the humor or bizarreness of statements made by someone who is attempting
to pull their leg. It's also called The Mr. Data response
in some circles. ^_^

P.S. They often get mad when someone like me is teasing them.

TDD

The only theoretical justification I can come up with for having 2 same type
and batch thermal fuses in series is this possibility.
Over time they were getting returns where the then single fuse had blown but
no one could work out whether its due to heat or current carrying. Assuming
they have space to mount 2 in at production and one is closer to the
monitored source of heat than the other. Then if practically all the returns
showed the hotter one to have failed then its not so likely the cuurrent
carrying self-heating that is the issue.

 

[JW]

On Fri, 23 Mar 2012 07:04:16 -0500 The Daring Dufas
<the-daring-dufas@stinky.net> wrote in Message id:
<jkhorv$6ho$1@dont-email.me>:

^_^

Speaking of emoticons, those look like emoticons used by the late Matthew
Moulton, AKA DiaperBoy. Hmmm...

 

[The Daring Dufas]

On 3/23/2012 7:46 AM, JW wrote:

On Fri, 23 Mar 2012 07:04:16 -0500 The Daring Dufas
the-daring-dufas@stinky.net> wrote in Message id:
jkhorv$6ho$1@dont-email.me>:

^_^



Speaking of emoticons, those look like emoticons used by the late Matthew
Moulton, AKA DiaperBoy. Hmmm...

Hatter isn't the only one to use them, they're actually common in Asia.
Besides, Matty was loads of fun to screw with and watch him melt down.

TDD

 

[The Daring Dufas]

On 3/23/2012 7:43 AM, N_Cook wrote:

The Daring Dufas<the-daring-dufas@stinky.net> wrote in message
news:jkhorv$6ho$1@dont-email.me...
On 3/23/2012 5:44 AM, N_Cook wrote:
Michael A. Terrell<mike.terrell@earthlink.net> wrote in message
news:OeGdncrMOvJ61_HSnZ2dnUVZ_iydnZ2d@earthlink.com...

N_Cook wrote:

Perhaps the voltage rating was lower than the required use, ie in
fused
state not rated for the service voltage across the broken section so
someone
thought, I know , we'll put 2 in series ;-)


Which would do nothing, if they couldnn't handle the voltage.

Have you ever looked at the wiring in a furnace? They use multple
thermal shutdowns, for liability in the US.


--
You can't have a sense of humor, if you have no sense.


so you have no visual sense for emoticons



It's known as H.I.S.I., pronounced "hissy", it describes the disease
Humor Irony Sarcasm Impairment. People with that particular mental
disease are said to have H.I.S.I. fits and often put on a big display of
pseudo-intellectualism about the subject at hand when they fail to see
the humor or bizarreness of statements made by someone who is attempting
to pull their leg. It's also called The Mr. Data response
in some circles. ^_^

P.S. They often get mad when someone like me is teasing them.

TDD


The only theoretical justification I can come up with for having 2 same type
and batch thermal fuses in series is this possibility.
Over time they were getting returns where the then single fuse had blown but
no one could work out whether its due to heat or current carrying. Assuming
they have space to mount 2 in at production and one is closer to the
monitored source of heat than the other. Then if practically all the returns
showed the hotter one to have failed then its not so likely the cuurrent
carrying self-heating that is the issue.

I do believe I wrote something like that early in the thread. ^_^

TDD

 

[Jeff Liebermann]

On Fri, 23 Mar 2012 13:33:04 +1100, "Phil Allison" <phil_a@tpg.com.au>
wrote:

"Jeff Liebermann"

The coffee distillery is double insulated, which means it doesn't need
a ground pin on the power plug. Since a fault can affect either side
of the power line in such a symmertical arrangement, two fuses are
required.

** Horse manure.

Yep. My neighbors just unloaded some Llama manure in their "garden".
Doesn't smell too bad.

One fuse is sufficient to break the circuit in case of current overload.

<http://www.freewebs.com/valvewizard/fuses.html>
Some appliances use two fuses, one for live and one for
neutral. While there is some argument against using a
neutral fuse, there is no law against it (in the UK anyway).
You can buy IEC inlet sockets with built-in fuse holders,
which greatly simplifies construction.

<http://www.appliance411.com/faq/dryerheat.shtml>
There are 2 fuses or breakers for the dryer, both must
be good in order for the dryer to function properly.

Note that the thermal fuses also act as an internal short
protector.

** Even worse horse manure.

Well, there are things worse than horse manure. I've never tried
skunk manure, but I suspect that would qualify.

Thermal fuses act on temperature, not current at all.

True.

The max current rating given by makers is based on self heating to ensure
the fuse stays within temp rating tolerance.

The max current rating is the maximum current at which it will operate
safely without self-heating and blowing the fuse. I found out the
hard way that it's much like the rating on a typical wire fuse. If
you run a 5A fuse, at 5 amps at room temperature, it will eventually
blow. Same with a thermal fuse. 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. With a short circuit across
the power line, the self-heating will blow the thermal fuse almost
instantly. It's not designed to be a power fault protection device,
but does the job nicely anyway.


--
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 Thu, 22 Mar 2012 19:30:18 -0400, jeff_wisnia
<jwisniaDumpThisPart@conversent.net> wrote:

'Course the current miniscule size of todays 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 use a microscope camera:
<http://www.ebay.com/itm/260969643003> $30
I have it plugged into a junk computah and LCD display. The original
plan was to attach it to a wrist strap, to make it easier for me to
see what I'm doing while soldering, but that didn't work. So, I now
use it on a plastic camera tripod, which works well. Saving the JPG's
has been handy for recording my work.

Unfortunately, I still have to wear my reading glasses in order to see
the LCD display. You can also use some cell phone cameras as a
microscope, if they have auto-focus (iPhone 3GS, most Droids, etc).



--
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