Why thermal fuses in series?

Discussion in 'General Electronics Chat' started by Gdrumm, Jul 20, 2010.

  1. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
    684
    36
    I was recently working on an old coffee pot, and found that it had two thermal fuses, in series.

    Any ideas as to why?

    They were rated the same.

    Thanks,
    Gary
     
  2. timrobbins

    Active Member

    Aug 29, 2009
    318
    16
    They are most likely put in positions that best monitor overheating in the pot. Were they in different locations, and were the locations a good choice to detect possible problems, or protect sensitive areas - could be a few reasons for their placement.

    I use them on heatsinks. I've seen them retrofitted into audio amps on heatsinks in line with speaker connection. They will most likely be in any commercial device with heaters (irons, hair dryers, radiators, oil heaters).

    They are very cheap and pretty reliable - I've only come across a few failures in ul rated devices. I think they are sometimes mandated in standards.

    Ciao, Tim
     
  3. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
    684
    36
    That makes sense, they were each near an end of the heater tube.

    I didn't pay attention to their orientation (the wax plug end), but it was probably nearest the end of the tube.

    Thanks,
    Gary
     
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