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EcoSmart Thermistor Long metal tips, Black and Red Wires THRM QC S103

Original price $34.99 - Original price $46.94
Original price
$34.99 - $46.94
Current price $34.99

NOT for the ECO36.

Also 100% compatible with the following heater models:
≈ iHeat/Drakken AHS27D, AHS18D, AH27, AH18
≈ Eemax HomeAdvantage HA018240, HA027240
≈ Eemax ProAdvantage PR018240, PR027240
≈ Eemax EEM24018, EEM24027 (blue color units)
≈ Rheem RTEX-18, RTEX-27
≈ Rheem RETEX-18, RETEX-27
≈ Richmond RMTEX-18, RMTEX-27


Thermistor part for EcoSmart ECO 18, ECO 24 ECO27


NOTE: Make sure you choose the correct size for your water heaters! NO RETURNS ON THIS ITEM.

MAKE SURE YOUR THERMISTOR TIPS (plug connectors) EXACTLY MATCH as shown in the product photos above! You may call EcoSmart tech support for assistance at 877-474-6473.

Thermistor Long metal tips. Black and Red Wires

  • Sizes: Medium/Large, and Xlarge

Thermistor Size Medium/Large (Long metal tips. Black and Red Wires): Compatible with models 18kW, 24kW & 27kW

Thermistor Size XLarge (Long metal tips. Black and Red Wires): Compatible with models 36kW


ECO 18, ECO 21, ECO 24 and ECO 27 Thermistors Troubleshooting Steps
Turn off breaker.
Unscrew cover.
Locate temperature sensors on inlet and outlet pipes. It is the nut with wires coming out of it.
Follow cable to electronic board.
Remove electronic board cover.
Disconnect from board.
Turn on breakers.
Turn on hot water tap.
Wait 3 to 5 minutes.

If water still does not heat up, further technical troubleshooting is needed. Volt meter is required.

If the water heats up, then the thermistors are bad. Just leave them disconnected (creating a bypass) until you can replace the thermistors.

EcoSmart tankless water heater technical overview

The ECO 18 is the medium sized model and carries (2) heating elements and exchangers using (2) 9 kW @ 240 Volts.
The ECO 21, ECO 24, ECO 27 and ECO 36 have the largest-sized form factor and they each use three heating elements and exchangers. The ECO 21 uses three 7 kW elements running at 240 Volts. The ECO 24 uses three 8 kW elements operating at 240 Volts. The ECO 27 uses three 9 kW elements running at 240 Volts. The ECO 36 uses four 9 kW elements running at 240 Volts.

Parts Description
1. Electrical Conduit Connection
2. Flow Sensor
3. Ground Connector
4. Terminal Block
5. Triac Cooling Plate
6. Triacs
7. Temperature Control Setting Knob
8. Inlet Temperature Sensor (thermistor)
9. Electronic Board and Protector
10. Fuse and Fuse Holder
11. Copper Heating Elements
12. Thermostats
13. Mounting Bracket
14. Back Casing
15. Copper Heat Exchanger
16. Outlet Temperature Sensor (thermistor)
17. Hot Water Outlet Connection
18. Cold Water Inlet Connection