Comprehensive Guide: How to Override MRCOOL Thermostat

The MRCOOL thermostat is a crucial component of the MRCOOL Ductless Mini-Split System, allowing users to precisely control the temperature and climate in their living spaces. However, there may be instances where you need to override the thermostat’s default settings to achieve your desired temperature and comfort level. This comprehensive guide will provide you with a step-by-step approach to overriding the MRCOOL thermostat, including both the Comfy feature and advanced methods involving electrical circuits and resistance measurements.

Overriding MRCOOL Thermostat Using the Comfy Feature

The Comfy feature is a convenient way to override the MRCOOL thermostat without delving into complex electrical modifications. This feature allows you to program a temperature range for the system to automatically turn on when the room temperature is 1 degree higher or 1 degree lower than the optimal temperature.

To set up the Comfy feature using the MRCOOL app, follow these steps:

  1. Open the MRCOOL App: Launch the MRCOOL app on your smartphone or tablet and tap on the AC icon.
  2. Select the AC Unit: Choose the specific AC unit for which you want to set the Comfy mode.
  3. Set the AC Mode: Set the AC unit to the “Cool” mode and adjust the temperature to 1 degree Fahrenheit cooler than the desired Comfy range.
  4. Navigate to eSaver: Tap on the “eSaver” option in the navigation bar of the app.
  5. Access My Rules: Select the “My Rules” option within the eSaver menu.
  6. Set the Comfy Temperature Range: Configure the temperature range for the Comfy mode, ensuring that it aligns with your preferred temperature settings. For example, if you choose a range of 68-70 degrees Fahrenheit, the AC unit will automatically turn on when the room temperature falls below 68 degrees or rises above 70 degrees.

It’s important to note that to utilize the Comfy feature, you’ll need a MRCOOL Ductless Mini-Split System, a MRCOOL WiFi Dongle, and a stable internet connection.

Overriding MRCOOL Thermostat Without the Comfy Feature

how to override MRCOOL thermostatImage source: nan

If you prefer to override the MRCOOL thermostat without using the Comfy feature, you can employ a more advanced method involving the use of a relay and resistance measurements. This approach allows you to “fake” the MRCOOL mini-split system into thinking the room temperature is either very cold or very hot, triggering the desired heating or cooling response.

Here’s a step-by-step guide to overriding the MRCOOL thermostat without the Comfy feature:

  1. Identify the Thermistor: Locate the thermistor, which is the temperature sensor within the MRCOOL mini-split system. This component is typically connected to the main control board via a wire.
  2. Cut the Thermistor Wire: Carefully cut the wire running to the thermistor, ensuring that you have access to both the wire leading to the control board and the wire connected to the thermistor.
  3. Measure the Resistance: Using a multimeter, measure the resistance of the thermistor wire. This will provide you with the baseline resistance value that the MRCOOL system expects to see.
  4. Adjust the Resistance: To override the thermostat, you’ll need to set the resistance to a specific value that will make the MRCOOL system think the room temperature is either very cold or very hot. This can be achieved by connecting a relay and a resistor in series with the thermistor wire.
  5. Connect the Relay and Resistor: Attach the relay and resistor to the thermistor wire, ensuring that the resistance value matches the desired temperature you want to “fake” the MRCOOL system into thinking.
  6. Program the Relay: Program the relay to switch on and off at the desired temperature thresholds, effectively overriding the MRCOOL thermostat.

This method requires a good understanding of electrical circuits and resistance measurements, as well as the ability to safely work with the MRCOOL mini-split system’s components. It’s essential to exercise caution and follow all safety protocols when attempting this approach.

Additional Resources

For more information and technical details on overriding the MRCOOL thermostat, you can refer to the following resources:

  1. MRCOOL Blog: Comfy – New Smart Controller Features
  2. SmartThings Community: Controlling a Minisplit Wall AC Directly from Nest/Ecobee Without Flair
  3. MRCOOL Blog: Follow Me Function

Remember, overriding the MRCOOL thermostat can be a complex process, and it’s essential to exercise caution and follow all safety guidelines to avoid any potential issues or damage to your MRCOOL Ductless Mini-Split System.