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CAT # THM-4 (3 Reviews) Write a Review

$6.00 each
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Product Description
Digital module can be programmed to turn equipment on or off at specific, pre-set temperatures. Also has hysteresis setting, delay setting, upper-limit setting and upper limit alarm setting. Displays temperature in Celsius on 3-digit LED display. On-board 20A relay. Waterproof temperature sensor. Three buttons for navigating temperature parameters and other functions. Operating voltage 12 Vdc. Overall dimensions 48mm x 40mm x 14mm.
Spec sheet available in PDF format.
WARNING: May cause cancer or reproductive harm.
California Prop. 65
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Customer Reviews (3 Reviews)

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Capable package, great price

Reviewer: from Hampton Bays, NY

Good capability for the price, but here are some considerations:

- Can only display in degrees C.
- Maximum temperature is 110 C both for setpoint and alarm.
- Minimum temp. is -39 C.
- Total sensor length is about 12 inches, but could be extended.
- Can be configured for heating (relay contacts open on reaching temp.) or cooling (contacts close).
- Relay contacts Normally Open when unit is unpowered.
- Relay case shows contact rating of 20 Amp. at either 14 VDC or 125 VAC, although I would use
it to operate a heavier duty mechanical or Solid State Relay for continuous currents that high.
- Comes with a single page of instructions that are easy to follow.

28 of 28 people found this review helpful. Do you? Yes No  Certified buyer

Device Looks Good, A Little Tough to Program

Reviewer: from USA

I bought 8 of the THM-4s to replace defective thermostats in electric space heaters. The THM-4 needs 12VDC, but they don't tell you what voltage range it can use. Powered by 12.0 VDC it draws 30mA when the relay is not engaged and 80 mA when relay pulls in.
When being programmed, the device will switch back to "idle" mode if you stop pressing the buttons for more than a few seconds. Best to have a list of the parameters and values you want to program before you start.
Press and release SET button to program the temperature set point (press + and - buttons to change value).
Press and hold SET for 5 seconds to access parameters P0 through P6. After "P0" appears in the display, use + and - buttons to select the parameter you want. Then press SET again to access the parameter value. Use + and - buttons to get the value you want. Press SET again to go back to the list of parameters to select another.
The display shows "LLL" if the temperature sensor is unplugged.
I have not used the THM-4 enough to know how the relay will stand up to a 13amp/120VAC heater load switching maybe several times an hour 24/7. I am prepared to use 40A solid-state relay if the on-board relay can not take it.

14 of 14 people found this review helpful. Do you? Yes No  Certified buyer

Great deal!

Reviewer: from Chester, Ca

Very accurate. Easy to program. For heating AND cooling. Buy an extra and you will find a use for it.

10 of 10 people found this review helpful. Do you? Yes No  Certified buyer

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