Measuring tools: Test items: Relative Humidity, Wet Bulb Temperature, Dew Point, Overheating Background: Single-level residential refrigeration equipment. The homeowner complained that the humidity was too high at the desired thermostat settings. Observations: The houses are low-rise bungalows; air handling units and piping systems are located in the attic; concrete structures; carpets indoors; temperatures set at 74 °F; air conditioning systems were installed last summer and were based on "mixed/wet" temperatures. The district's ACCA best method calculates the load. Action: You think this is too simple. It may be related to the system (dust filter, low voltage, dirty condenser, etc.). But you also realize that at that time the weather is cooler than most of the summer to. You measured the room temperature and relative humidity and found that the temperature and humidity were 74.5 °F, 68% RH, 66 °F WB, and 63.3 °F DP. * You think the problem is related to the following reasons: the weather is cooler than usual summer, the equipment works less time (less moist air is discharged), the carpet on the concrete hides the moist gas and forms an environment conducive to the breeding of fungi. You also want to know if there is a layer of sand that can hold moisture between the moisture barrier and the concrete floor, which will exacerbate the problem of moisture under the carpet. The carpeted floor was measured using a Fluke 60 series infrared thermometer and the measured temperature was 68 °F. This temperature is higher than the dew point. It is known from the chart that the vapor pressure in the carpet is higher than the vapor pressure in the air, so the moisture will flow from the carpet to the air. This condition is good for carpets, but it will cause higher relative humidity in the living space. This is advantageous because the problem of handling relative humidity is simpler than dealing with the wetness of the ground. You asked whether the homeowner had transformed the house. They said: "No. Wait. We have installed a new roof. Is that okay?" You asked again: "The roof of the same structure?" They said: "Yes , but we changed the aquamarine to white." You said: "Thanks. I also noticed that you kept the fan on all the time. Is there any reason?" They said: "We think that will keep the air flowing. Make the house more comfortable." You think that you should make comments after you have collected the data. You open the insulation and find that there is a pipe seam that is not well welded. This can explain the reason for the drop in temperature at this location. You rewelded the seams, wrapped the insulation, and resealed the cadmium gas layer. So far, to solve the problem before it becomes more serious, you are confident that the foil overlay will stay above the dew point and turn your attention to the issue of indoor relative humidity. The filter is relatively clean, you reinstall it and check the evaporator. The evaporator is also clean but not horizontal. The water behind the pan is higher than the drain. You are fortunate that the evaporator and the stove are connected with basket screws. You adjust the basket screw to get the best drainage. This will help prevent moisture from being drawn back into the airflow during the off period, but you want the evaporator to use a TXV (thermal expansion valve) instead of a fixed current limiting device because you know that TXV is at partial load Can provide better performance. Optional measures: Now you need to determine what measures to take to improve performance under partial load conditions. 1. The performance has been initially improved by rearranging the condenser water tray to allow better drainage. 2. It is recommended that the homeowner put the fan in an “automatic†state to reduce the re-absorption of moisture during the shutdown cycle. 3. You tell them to use a best-quality electronic thermostat to adjust the temperature difference setting. You are sure to change the temperature difference from 1 °F to 1.5 °F to make the opening time longer and get a more stable dehumidification time. 4. You measured the Delta-T of the evaporator at 18 °F using a Fluke digital multimeter and two 80PK-26 universal temperature probes. You can reduce the speed of the air supply, but it is not possible to determine the temperature of the pipe surface in other operating conditions. 5. Replace the fixed restrictor valve with TXV. Replace the wavy evaporator with a straight-plate evaporator so that the fin spacing is greater. Because wavy heat sinks store more water, and the smaller the heat sink spacing, the more water
Temperature and humidity meter, pipe clamp probe, IR thermometer, digital multimeter