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How to Troubleshoot a Chilled Water Fan Coil Unit

Chuck Brown

Contrary to popular belief, many people are not all that fond of the dramatic transition between the warm outside temperature and the supercooled air of some houses and stores. Energy conscious people are increasingly opting for slight cooling, as opposed to a 20-degree difference between their interior living space and the outside. One way to more effectively regulate cooling and target specific hot areas is using by wall air conditioners. These chilled water fan coil units are easier to troubleshoot than their whole-house counterparts.

Single-room wall units eliminate the need for window units.

Step 1

Start the troubleshooting process by turning the unit on. Turn the unit off if it fails to come on when you activate the switch. Open the unit cover, and check the fuse. Pull it out and hold it against a white or lit background to make sure it is not blown. Replace it if it is blown.

Step 2

Check the power plug. Make sure it is completely pushed into the outlet. Unplug the unit and inspect the plug for damage. Use a current detector/probe to confirm there is power to the outlet. Look at the delay timer to verify that it is set correctly, if all power checks are good.

Step 3

Place your hand on the vent to confirm that there is even, strong air flow from the unit. Run your hand along the entire length of the vent to detect any variance in air flow rate. Raise the unit cover and check the condition of the filter if you do not feel strong, even air flow.

Step 4

Lift the air filter out and examine it carefully for any accumulated dust, lint or other obstructions. Replace the filter if it is too dirty to blow out or clean. Check and shut all the doors and windows to the room if you feel weak air current coming from the unit, and that there is sufficient temperature change demand on the unit for it to run.

Step 5

Inspect the air suction and discharge for clogs if the filter is good and all windows and doors are shut, and you still are not getting sufficient air flow. Clear the intake and exhaust areas of any blockages.

Step 6

Take a look at the coil if the unit is emitting an odor. Turn off the unit and inspect it carefully to find any coating from cigarette smoke or other air contaminants that has adhered to the surface of the coils.

Step 7

Wipe the coils clean with a clean, dry cloth. Use a white cloth to better see what you actually wipe off. Restart the air conditioner and repeat the odor test, repeating the process until the coils are clean and odor-free.

Step 8

Monitor the unit after it has run for an extended time. Check the front of it for condensation. Raise the temperature setting of the unit by 5 degrees and increase the fan speed to dry the moisture.