Issue link: https://hi.iaq.net/i/248503
www.epa.gov/iaq/moisture Control Sequence Guidance 1: Maintain HVAC system components in accordance with the manufacturer's requirements and the moisture control recommendations in this guidance. At a minimum, the following HVAC components should be inspected as part of a PM program: • Make sure the clocks on all systems read the correct time and date (if applicable); adjust if necessary. • Check that equipment is turned off or energized according to the control sequence. (Observe the actual operation of fans, dampers and valves as well as the operation of the control unit.) Thermostats • Thermostats should be checked in the fall and spring, shortly after switching to or from daylight saving time, or whenever complaints about thermal comfort are received. Outdoor Air Intakes • Inspect the area around intakes for potential contaminant sources such as dumpsters, garbage cans, decaying organic matter and automobile idling or parking areas. If there are contaminant sources near the intakes, move them if possible. If contaminant sources are not mobile, other steps may be required to prevent the intake of airborne contaminants. These steps may include relocating intakes or instituting policy changes such as prohibiting vehicle idling. Checking Thermostat Operation and Calibration • If the thermostat is programmable, make sure the time is set correctly and the thermostat is programmed for the hours when the building is occupied. • Place a calibrated thermometer next to the thermostat. Place a paper towel or other material between the thermometer and the wall to make sure the wall temperature is not influencing the thermometer reading. • Inspect the outdoor air intake louver and the debris screen behind it. Check for signs of rain leaks and clogged screens. If rainwater intrudes into the outdoor air intake, modify as needed to prevent entry. Remove grass clippings, leaves, dust and other materials that obstruct the air intake. Take care when doing this during the warmer months because bees, wasps or other stinging insects may have nested in the intake. NOTE: Do not use a pesticide if insects are found in the outdoor air intake. • Allow the thermometer to stabilize. How long this takes will depend on the thermometer used. • Compare the thermostat and thermometer readings. If the thermostat differs by more than 1°F, there is a problem and you should do the following: yy Remove the faceplate and check whether the thermostat is dirty. Carefully brush or blow away any accumulated dust. • If outdoor air intakes are close to ground level, ensure that all landscape plantings are at least 5 feet from the intake. Require lawns to be mowed in a manner that directs the cut grass away from the building and the intakes. yy If contact points are accessible, clean them with a soft cloth. Do not use sandpaper or other abrasive materials. yy If the thermostat has a mercury switch, check that it is level. Be very careful not to break the vial that contains the mercury. Outdoor Air Dampers yy Check behind the thermostat to make sure the hole for the wires is caulked to prevent air within the wall from influencing the thermostat reading. • Determine the outdoor air damper control sequence, then change the parameters to force the dampers to open and close. Do not rely on observing linkages; watch the outdoor air dampers for movement. Make necessary repairs to ensure dampers open and close in accordance with the control sequence. yy Allow temperatures to stabilize and compare the thermostat and thermometer readings again. If they still differ by more than 1°F, replace the thermostat. • Measure outdoor air volumes on a regularly scheduled basis and whenever indoor air quality problems arise. Either purchase equipment such as balometers, anemometers, manometers and pitot tubes to take these measurements, or hire a qualified contractor. 100