Defrost thermostat Introduction for Beginners

Defrost thermostat Introduction for Beginners


Last updated on June 30th, 2023 at 05:34 pm

Please learn that all of our defrost thermostats are for thawing the frost on evaporation but not condenser or other coilers

Why use the defrost thermostat?

The ice or frost is the most common cause of inefficiency in evaporator coils, to improve the efficiency of the evaporator, you could install a defrosting unit like a heating mat on the evaporator, or just let it thaw naturally, or make the compressor reverse roll to get hot gas; No matter which kind of method you will take,  you just need a dual function digital thermostat, which owns both the ability of refrigeration control and defrosting process managing, that is what defrost thermostat does.

Here is a good post about “Commercial Refrigeration Temperature & Defrost Control and Optimization”  from KE2 Therm Solutions Inc, which will help you to learn more about the frosting process.

Haswill-Electronics offers multiple universal defrost thermostats for refrigerators, and part of them could control the evaporative fan or output signal to an external alarm, what is the purpose, and what is the difference between them? which one is the most suitable for you?

This page will help you fix this question, meanwhile, learn the features and benefits of each of them.

Basic Parameters

7 defrost thermostats compares

From the “Function” column of the above table, we could learn that

  1. The STC-8080A+, STC-8080H, and STC-2302 seem the same, we will analyze the difference between them in this article;
  2. The STC-2304 and the STC-9200 looks the same, please read 6 difference between STC-9200 and STC-2304 for more details of the difference;
  3. The STC-9100 with a unique feature that controls the external alarm output function, but it adopts the same hardware as the STC-9200.
  4. For more differences between STC-2302, STC-2303, and the STC-2304, please read Touch-sensitive keys thermostat 

Although there are seem the same in the function column, however, we will find more differences from the other columns, e.g. push-type buttons or touch-sensitive keys, the measurable and the controllable temperature range; Delay time is editable or fixed, the mount size, the front panel dimension, and more.

As the below menu shows, we divide them into 3 types.

Defrost Thermostat Types

  • 2 Relays, Refrigeration + Defrost
  • 3 Relays, Refrigeration + Defrost + Alarm
  • 3 Relays, Refrigeration + Defrost + Fan

The Differences in Functions

Let’s make a comparison from the function menu list, to find what distinguishes the existence of each digital defrost thermostat.


  • Slide left and right to see more columns if more than 5 Products.
  • or download the PDF; or view it on Google Sheet

ON TEMP / Startup TemperatureF1F1shortcutshortcutshortcut
OFF TEMP/ Stop TemperatureF2F2shortcutshortcutshortcut
Defrosting Lasting TimeF5F8F1F1F1
Defrosting Cycle / Interval TimeF4F7F2F2F2
Defrosting Cycle / Interval Time Count mode××F3F3F3
0: The sum working time of the controller××
1: The sum working time of the compressor××
Water dripping Time××F4F4F4
Defrosting by,××F5F5F5
0 = Electric-Thermal, ××
1 = Hot Air, ××
2 = Natural Wind××××
Defrosting Stop Temperature×××F6F6
Fan mode××××F7
Delay Time for the fan 1st time running
(count time from the water dripping over moment )
Editable Delay Time for Compressor Protection×F4F9F9F9
Alarm Delay time T1
(count time from the controller power on)
Over-Temperature Value to Trigger AlarmF6F5F11F11F11
Alarm Delay time T2 after T1
(count time from the T1 over moment)
Calibration = Real - Measured TemperatureF3F3F13F13F13

As the defrost controller for the refrigerator, all of them offer 2 essential options, the refrigeration defrost cycle time and the interval/loop time, we will not make a deeper discussion here, now let’s see the differences.

STC-8080A+ and STC-8080H are almost the same except

  • 8080H offers an editable delay time for the compressor protection, on the other hand, the 8080A+ owns a fixed 3min delay time;
  • 8080H supplies an editable delay time for alarm, 8080A+ without this option.

As we mentioned above, The STC-2302 and the STC-8080A+/H look the same, but you will find from the above comparison table that, STC-2302 owns

  • the additional refrigeration defrost timer count mode for thawing;
  • the additional water dripping time;
  • the additional defrosting units types, by Electric-Thermal or hot air for selection
  • the editable delay time for compressor protection
  • two alarm time delay settings.

STC-8080A+/H has no above features, however, STC-2303 owns all the features like the STC-2302, and one more option, is the defrosting stops temperature F6, with this option the thawing progress will stop even if the last time has not run out, this will prevent the evaporator become not cold.

More Differences

You will find more differences from the manual of each defrost controller, For instance, the different methods to set the ideal temperature range, All STC-230x offers the shortcut key to set it, but you have to enter the menu list to set it in STC-8080A+/H.


Different models of our defrost controllers for the refrigerator have different characteristics, which can be summarized as follows

  1. STC-8080A+ with fixed 3min compressor delay time, and the alarm function without delay;
  2. STC-8080H with editable protection time for the compressor, Besides, it offers a changeable alarm time delay option;
  3. STC-9100 owns all functions like the STC-8080H, furthermore, it prepared the 3rd relay for external alarm, the 2nd sensor for evaporator temperature measuring, and offer more controllable elements related to defrosting;
  4. STC-9200 is a defrost evaporator like 9100, but the 3rd electronics channel for fan control.
  5. STC-2032 & STC-2033 own all features of STC-8080H, meanwhile, it offers extra timer mode, water dripping time, thawing unit types, and an extra-alarm time delay setting for the 1st-time boot period.
  6. STC-2303 thawing thermostat offers a stop-thawing temperature option like STC-9X00, which is why it owns 2 sensors, others just need 1 NTC probe.
  7. STC-2304 is nearly as same as the STC-9200 and could control fan action, moreover, it holds all the features of STC-2303.

At last, let’s stress it again, all of our defrost thermostats offer the below features

  • working on evaporation defrosting;
  • the over-temp alarm by visible and audible methods;
  • Artificial forced defrost available;

If you still have difficulty when choosing a suitable one from the below defrost temperature controllers, please contact Haswill-Electronics or visit all refrigeration thermostats.