(This is related to question How to solder a 70 °C (158 °F) thermofuse).

Would it be a good idea to use a temperature/thermal fuse inside a terminal block like the picture below.

I see only benefits:

  • No problem destroying the fuse because of excessive heat (no soldering needed)
  • Solid tight to the PCB
  • When the fuse blows, it is very easy to exchange it.

Are there reasons why not to do this?

(and what about doing the same for VST diodes?)

enter image description here

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    \$\begingroup\$ Any reason you are not using a resettable? \$\endgroup\$ – PlasmaHH Oct 16 '18 at 13:07
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    \$\begingroup\$ @– MichelKeijzers: "Resettable thermal fuse" should be a good search term \$\endgroup\$ – PlasmaHH Oct 16 '18 at 13:10
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    \$\begingroup\$ @MichelKeijzers there are even latching ones which require a power cycle to reset. The design of those is a bit more involved (they use a heating resistor which gets turned on in case of over temperature to keep the over temperature). \$\endgroup\$ – Arsenal Oct 16 '18 at 13:15
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    \$\begingroup\$ @MichelKeijzers: I would consider it in a device that needs to be safe, and that under no normal operating conditions should ever overheat. \$\endgroup\$ – PlasmaHH Oct 16 '18 at 13:31
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    \$\begingroup\$ @MichelKeijzers: It is an answer for a different question. Your actual question would have a different answer that some other visitor might have asked. \$\endgroup\$ – PlasmaHH Oct 16 '18 at 13:35

In a commercial project the main disadvantage would be cost. A terminal block requires space and additional space to access it (might not be available at the point where the fuse should sit).

And it probably requires manual labor to mount it, which is also costly.

For a low volume product I don't see a problem with that approach. You could even market it as easily repairable.

From a technical standpoint I don't see a problem with the terminal block as long as the current carrying capability is high enough. If the block fails, it probably fails open, which is the safe state of the fuse, so that is good.

As mentioned in the comments, there are resettable fuses available. In some situations those might not be the preferred solution as the device turns on again after the fuse got cold. As the fuse should only act on a quite severe failure, that cycling could be considered bad (something gets more damaged).

For that there are latching resettable thermal fuses available where a heating resistor gets turned on when a failure occurs to keep the fuse in the open state until a power cycle occurs.

The cost for resettable fuses is usually higher and the current capability lower than the non resettable fuses I have come across so far. So that might be a reason why you can't use one of those.

  • \$\begingroup\$ Thanks for this comment... I ordered resettable fuses a few minutes ago (takes 2-8 weeks to receive but that's no problem). My project is far from commercial. I wouldn't even dare to ask money for it (it's for personal, well for usage in the band I play in). In my case I bought 73 degrees, so if it keeps resetting it will be no problem. I'm intending to build only one (I hope). \$\endgroup\$ – Michel Keijzers Oct 16 '18 at 13:43

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