Replacing thermal fuse in wall oven power supply.
Does fuse measure temperature of ambient, or, temperature based on current through fuse?
I ask because I would like to attach wire leads to fuse since I screwed up soldering directly to the board.
Thank you.

Ivan Vegvary wrote:
Replacing thermal fuse in wall oven power supply.
Does fuse measure temperature of ambient, or, temperature based on current through fuse?

It just measures heat, doesn't matter where it comes from. But-

Keep in mind heating the fuse with current will heat the inside to a
higher temp that just warming the outside as there is thermal resistance
of the device package to overcome.

Just be careful soldering the leads and you should be ok.

On 11/09/2015 8:40 AM, Ivan Vegvary wrote:
Replacing thermal fuse in wall oven power supply.
Does fuse measure temperature of ambient, or, temperature based on current through fuse?
I ask because I would like to attach wire leads to fuse since I screwed up soldering directly to the board.
Thank you.


Thermal fuses are supposed to open when their temperature rises above
their design failure point.

Certainly if you pass too much current through it will fail! Most
thermal fuses are on heat sinks or fans and open at relatively low
temperatures to indicate that the fan or cooling system has failed and
this helps to protect the electronics from heat failure.

Due to their sensitivity they are hard to solder without opening
internally! You MUST heatsink the leads to protect the element inside
the thermal fuse from getting too hot. A heatsink can be the jaws of
needle nosed pliers or similar clamp with lots of metal to absorb the
heat of soldering. I'm not certain that all types of thermal fuses can
even be soldered - most I've seen have metal clips clamping them to the
wires. You may have to experiment. You probably should get more than one
in case of failure...

Pigtail screw-on clips might work fine.

John :-#)#

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On 09/11/2015 18:36, John Robertson wrote:
On 11/09/2015 8:40 AM, Ivan Vegvary wrote:
Replacing thermal fuse in wall oven power supply.
Does fuse measure temperature of ambient, or, temperature based on
current through fuse?
I ask because I would like to attach wire leads to fuse since I
screwed up soldering directly to the board.
Thank you.


Thermal fuses are supposed to open when their temperature rises above
their design failure point.

Certainly if you pass too much current through it will fail! Most
thermal fuses are on heat sinks or fans and open at relatively low
temperatures to indicate that the fan or cooling system has failed and
this helps to protect the electronics from heat failure.

Due to their sensitivity they are hard to solder without opening
internally! You MUST heatsink the leads to protect the element inside
the thermal fuse from getting too hot. A heatsink can be the jaws of
needle nosed pliers or similar clamp with lots of metal to absorb the
heat of soldering. I'm not certain that all types of thermal fuses can
even be soldered - most I've seen have metal clips clamping them to the
wires. You may have to experiment. You probably should get more than one
in case of failure...

Pigtail screw-on clips might work fine.

John :-#)#


Another tip is to freezer spray the body of the thermal fuse before
pre-tinning the wires and then repeat freezing before soldering proper.

Ivan Vegvary wrote:


Replacing thermal fuse in wall oven power supply.
Does fuse measure temperature of ambient, or, temperature
based on current through fuse?


** Thermal fuses respond to the temperature of the case and are designed to have low self heating due to current flow. Makers specify the operating temp and also give a max continuous current rating at which self heating is not significant.


I ask because I would like to attach wire leads to fuse since
I screwed up soldering directly to the board.


** The thermal fuses I know have wire leads and look a lot like film capacitors or diodes. What have you got ?


..... Phil

Thanks everyone! Decided to crimp on some 2" leads and thereby keep soldering heat far away from the Thermal Fuse.
Your help is greatly appreciated.

In article ,
Ivan Vegvary wrote:

Thanks everyone! Decided to crimp on some 2" leads and thereby keep
soldering heat far away from the Thermal Fuse.
Your help is greatly appreciated.

Ivan-

When I've soldered a thermal fuse, I held a lead by a heavy pair of
pliers next to the body. The pliers had a rubber band around the
handles so my hands were free. So far there were no failures due to
soldering.

Some thermal fuses are supplied with a little brass sleeve for crimping.
However, it is difficult to get a good crimp between two solid wires.
Be sure you crimp to a stranded wire with the solid wire in the same
bundle.

Fred