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I've got a PTC thermistor, as pictured. It's being used to detect the output temperature in an in room eletrothermal storage (ETS) unit from Steffes.

One of them fell out. It's like some kind of rough material on the outside and I have no idea how they ever got it to adhere to the board in the first place. Also, the one that fell out is damaged a bit.

Anyway, how would I reattach it? What soldering technique was used to get the one on there on. BTW, I found something like them by the 2500 at digikey. It says "clamp on", maybe that's why the other one fell off, these are just held in by the tension on the wire? That doesn't seem right.

Also, how would I identify just what the specs of the thermistor are? I have some hints. The thermal fuses have two different ratings, the lowest of which is about 160°C and there is 250V going to the board (AC, home heater connection).

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    \$\begingroup\$ What is a "steffes output board"? \$\endgroup\$ – Hearth Feb 13 '19 at 4:52
  • \$\begingroup\$ Steffes is a manufacturer of Electric Thermal Storage units. steffes.com/electric-thermal-storage \$\endgroup\$ – MrGerber Feb 13 '19 at 12:16
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    \$\begingroup\$ Your best bet is probably to go to the manufacturer. Resistance and temperature coefficient are two parameters, as well as the physical characteristics. Usually temperature measurement thermistors are NTC. \$\endgroup\$ – Spehro Pefhany Feb 13 '19 at 12:17
  • \$\begingroup\$ OK, I tried to get something out of the manufacturer. They were willing to give up that the heater is designed to operate at about 93°C output and it sounded like the circuit is designed to open at that temperature. And I know that they're about 500 mohm closed. But I can't seem to find anything with similar specs that can handle 250 VAC. \$\endgroup\$ – John Feb 22 '19 at 3:36

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