Do thermal fuses fail from old age?

J

jeff_wisnia

Guest
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.
 
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

Hi,
Click to expand...
I understand they work on bi-metal strips. They can fail from fatigue.
Won't reset when temperature goes down cooling off.
 
"Tony Hwang"

I understand they work on bi-metal strips.
Click to expand...

** 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
 
"Larry Fishel"
"Phil Allison" :
"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.
Click to expand...
But I assume the same applies. The metal heats up and expands somewhat
when in use and contracts when not. That will eventually cause it to
fail


** Maybe so - but has nothing do with bloody bi-metal strips.



..... Phil
 
On Mar 22, 12:17 am, "Phil Allison" <phi...@tpg.com.au> wrote:
"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.
Click to expand...
But I assume the same applies. The metal heats up and expands somewhat
when in use and contracts when not. That will eventually cause it to
fail.
 
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?
Click to expand...
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?
Click to expand...
May it be our biggest problem.
Thanks guys,

Jeff
Click to expand...
 
I repair machines that use use them for a living, they are cheap
protection. they definetely nuisance trip for no reason. oh well it
keeps me working:)

they are so commonly used because of being so cheap. but it would be
far better if a resettable kind were used. lots of perfectly good
stuff must be tossed every year because a thermal fuse fatigued
failed.

I service roll laminating machines for a living. sael, GBC, Laminex,
USI, Idex, Ledco. Sadly nother manufacturer Banner just went out of
business after 38 years.

the economy is far worse than were being led to believe...............:
(
 
"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
Click to expand...

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.
 
"Gareth Magennis"
"Phil Allison"
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


This is the type Peavey have hidden in the mains transformer of the
Classic
30.
Click to expand...
** Eeee - yep.

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?
Click to expand...

** We must be leading parallel lives ..........

I actually have a power tranny from a PV Classic 30 in my used parts bin.

The thermal fuse was open - it resembled the one in my pic.

I replaced it with a new one of slightly higher temp rating and it works
fine.

The customer got a new tranny, as requested.



.... Phil
 
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
Click to expand...
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? o_O

TDD
 
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.
Click to expand...

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.
 
On Mar 22, 12:03 am, jeff_wisnia <jwisniadumpt...@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?

Comments?

Thanks guys,

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10e12 furlongs per fortnight.
Click to expand...
I had one of the hot water dispenser tank settups that goes
under the kitchen sink. A few years in, it failed due to the
thermal fuse failing for no reason. The original was no longer
available and had been replaced by a different type of design,
attachment method, etc. Looks to me like they had a
problem with them and changed the design.

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.
 
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? o_O

TDD
Click to expand...
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.

Cheers

Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

hobbs at electrooptical dot net
http://electrooptical.net
 
Phil Allison wrote:
"Gareth Magennis"
"Phil Allison"
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


This is the type Peavey have hidden in the mains transformer of the
Classic
30.

** Eeee - yep.

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?


** We must be leading parallel lives ..........

I actually have a power tranny from a PV Classic 30 in my used parts bin.

The thermal fuse was open - it resembled the one in my pic.

I replaced it with a new one of slightly higher temp rating and it works
fine.

The customer got a new tranny, as requested.



... Phil

Hi,
Click to expand...
I fiddle with guitar amps. Son is into playing guitar/bass and drum.
Have a crude set up for recording as well. Have some vintage Marshall,
Fender, Boogie amp. Guytron and Soldano. Hugh & Kettner. Built couple
Fender clone and Marshall JMP clone from mono tube amp. Let kids blind
test it placing it side-by-side with real thing. They couldn't tell the
difference.
 
bob haller wrote:
I repair machines that use use them for a living, they are cheap
protection. they definetely nuisance trip for no reason. oh well it
keeps me working:)

they are so commonly used because of being so cheap. but it would be
far better if a resettable kind were used. lots of perfectly good
stuff must be tossed every year because a thermal fuse fatigued
failed.

I service roll laminating machines for a living. sael, GBC, Laminex,
USI, Idex, Ledco. Sadly nother manufacturer Banner just went out of
business after 38 years.

the economy is far worse than were being led to believe...............:
(
Click to expand...
Glad to hear that you've seen nuisance trips too, that makes me feel
like replacing the thermal fuse in our Bunn coffeemaker really "fixed it".

Jeff

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

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.

Cheers

Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

hobbs at electrooptical dot net
http://electrooptical.net
Click to expand...

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 ;-)
 
micky 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
Click to expand...
The one I replaced is about the size of a 1/2 watt carbon resistor and
looks like this:

http://parts.digikey.com/1/parts/726774-thermal-fuse-141c-10a-axial-sdf-df141s.html

The way the original was installed The fuse's leads were left about an
inch long and the flexible insulated wires connecting to them were
fastened with little uninsulated metal crimps. I didn't have any of
those crimps so I just clamped a heat sink to the fuse's lead wire and
quickly soldered the flexible wire to the fuse lead with an 1/8 inch
long lap joint.

(Probably more than you needed to know, eh?)

Jeff


--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10e12 furlongs per fortnight.
 
"Larry Fishel" <ldfishel@yahoo.com> wrote in message
news:8d34fb90-87dd-4f35-b801-484ef1fa60e1@i2g2000vbv.googlegroups.com...
On Mar 22, 12:17 am, "Phil Allison" <phi...@tpg.com.au> wrote:
"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.
Click to expand...
But I assume the same applies. The metal heats up and expands somewhat
when in use and contracts when not. That will eventually cause it to
fail.

That's right; it's "metal fatigue" and those fuses which carry current close
to their limits do wear out faster. I'll also add corrosion. The metal at
the contact points of the fuse corrodes and makes for an intermittent
contact. I had a car once with all kinds of electrical problems -- wouldn't
start, lights flashed, horn didn't work, then it did. Finally replaced all
the fuses and the problems disappeared.

Tomsic
 
Anything that heats up and cools down is likely to eventually fail from
thermal stress (including crystallization). (See Nevil Shute's novel "No
Highway".)
 
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.
Click to expand...

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


Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10e12 furlongs per fortnight.
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top