Clean & check call today.70% humidity,84 degree ambient.Delta-t(temp-split)only 10 degrees, but superheat running at 20.I know I can accept the 10 degree temp-split,but can I accept a 20 degree superheat with the house having all windows open durring my check with 84 ambient and 70% humidity? I don't want to overcharge customers systems and I know so many of you can answer this off the top of your heads.Please believe I very much appreciate the replies.
Does high humidity affect superheat readings?
grodan1
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Clean & check call today.70% humidity,84 degree ambient.Delta-t(temp-split)only 10 degrees, but superheat running at 20.I know I can accept the 10 degree temp-split,but can I accept a 20 degree superheat with the house having all windows open durring my check with 84 ambient and 70% humidity? I don't want to overcharge customers systems and I know so many of you can answer this off the top of your heads.Please believe I very much appreciate the replies.
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Maybe this will help you:
For a constant air entering dry bulb temperature, the DT across a coil increases with decreasing relative humidity. This is because the coil condenses a decreased moisture (latent) load. If a coil doesn’t have to condense much moisture from the air, it can perform more sensible cooling. Sensible cooling is what we are measuring. Humidity can account for several degrees of dry bulb deviation. Therefore, on a humid day, the sensible DT reading will be lower as more of the air conditioner’s capacity is used to dehumidify. Conversely, if the relative humidity of the return air is low, the sensible DT will be higher. On the average, about a quarter of an air conditioner’s capacity is used to dehumidify at 50% relative humidity. As an example, a 4 ton air conditioning system uses about 3 tons for sensible cooling, while one ton is used to dehumidify. This sensible heat factor (SHF) should be taken into consideration when taking the dry bulb DT over an evaporator to determine airflow. The dry bulb DT could vary from about 15oF, very humid return air, to 25oF, very dry return air. The 20oF DT is assuming about 50% relative humidity return air.
For a constant air entering dry bulb temperature, the DT across a coil increases with decreasing relative humidity. This is because the coil condenses a decreased moisture (latent) load. If a coil doesn’t have to condense much moisture from the air, it can perform more sensible cooling. Sensible cooling is what we are measuring. Humidity can account for several degrees of dry bulb deviation. Therefore, on a humid day, the sensible DT reading will be lower as more of the air conditioner’s capacity is used to dehumidify. Conversely, if the relative humidity of the return air is low, the sensible DT will be higher. On the average, about a quarter of an air conditioner’s capacity is used to dehumidify at 50% relative humidity. As an example, a 4 ton air conditioning system uses about 3 tons for sensible cooling, while one ton is used to dehumidify. This sensible heat factor (SHF) should be taken into consideration when taking the dry bulb DT over an evaporator to determine airflow. The dry bulb DT could vary from about 15oF, very humid return air, to 25oF, very dry return air. The 20oF DT is assuming about 50% relative humidity return air.
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