How to Adjust a Honeywell Thermostatic Mixing Valve

A thermostatic mixing valve regulates the temperature of the water in a hot water heater. It mixes the hot and cold water in the proper proportion to maintain the desired temperature. You can adjust the mixing valve to increase or decrease the maximum temperature. Honeywell recommends setting the mixing valve at a temperature no higher than 120 degrees Fahrenheit to prevent scalding. The specific directions for adjusting the valve vary, depending on which Honeywell model you have.

AMX Series DirectConnect

Step 1

Remove the temperature range label on the thermostatic mixing valve to access the temperature controls.

Step 2

Fit a 3/16-inch Allen wrench into the screw.

Step 3

Turn the wrench counterclockwise to raise the temperature, or clockwise to lower the temperature.

Step 4

Run hot water out of any faucet in your home. Use a thermometer to measure the temperature. Readjust the thermostatic mixing valve as needed to correct the temperature.

Proportional Thermostatic Mixing Valve

Step 1

Locate the hand wheel on top of the main valve body.

Step 2

Use a screwdriver to loosen the screw on top of the hand wheel. Don't remove the screw entirely.

Step 3

Lift the hand wheel slightly, but do not attempt to remove it. Lifting it allows you to adjust the temperature.

Step 4

Turn the hand wheel counterclockwise to reduce the temperature. Turn the wheel clockwise to increase the temperature.

Step 5

Press the hand wheel down gently to lock in the temperature setting. Tighten the screw.

Step 6

Measure the hot water temperature from any faucet in your home. Readjust the temperature setting as needed.

About the Author

Catherine Chase is a professional writer specializing in history and health topics. Chase also covers finance, home improvement and gardening topics. She holds a Bachelor of Arts in American studies from Skidmore College.