Do not reset chilled-water temperature up to save energy.However, it may raise energy usage and may not be possible with some equipment and controls. Real-time monitoring and alarming of humidity levels in the ORs require near-constant water temperature and this will keep the humidity levels in the ORs constant. Ensure that the chilled water temperature is a constant 42 degrees F (typically) because staging on and off chillers may cause spikes in the chilled-water temperature.This strategy saves energy and limits the amount of moisture brought into the AHU. Calibrate the air-flow sensor to ensure that more outside air is not being brought in than is minimally required.The advantage of this strategy is its low cost. The following strategies are ranked in order of estimated implementation cost, from least expensive to most expensive:

If conditions are not acceptable, there are steps that can be taken to improve the performance of an existing air-handling unit (AHU). Understanding that the driving factor of the relationship between the temperature being produced by the air handler and the humidity in the air helps the hospital engineer to properly operate the HVAC system. Related Article HAIs present facility challengesīeing able to maintain the lowest possible temperature in the OR that does not cause the relative humidity to exceed 60 percent is important to be able to avoid this risk. If the humidity levels exceed the allowable amount in the air, there can be an increased risk of infections. As this air is cooled, the humidity level in the air will increase. The air that enters the system will contain a certain amount of humidity. While it should be noted that every hospital system is different and will perform differently than the example given here, the concepts are the same. The concept of the beakers can be applied to how a typical HVAC system supplies air to the operating rooms (ORs) and can be explained by a simplified graphic (, upper right). A spreadsheet showing the calculations for a range of temperatures also can be found at the ASHE member link. Now the height of the 500-ml beaker represents 100 percent humidity, or dewpoint, at 90 degrees F. This is illustrated in a training video that can be accessed by American Society for Health Care Engineering (ASHE) members at The premise of using the beakers is to let 1 ml equal 1 grain per cubic foot and then calibrate amounts so that the moisture in the air at 90 degrees F will equal 500 ml. After many failed attempts, it was finally realized that it was much easier to explain psychrometrics and, more specifically, the relationship between temperature and humidity, by using 500 milliliter (ml) beakers.

Willis carrier psychrometric chart