I have one of those medium sized AC-units (don't know the model name at the moment) and a very basic Honeywell thermostat that the installers put in when the house was built. However, there doesn't seem to be much options. I can only turn the fan on or off, AC on or off, set the schedule, and the desired temp. Is there a way to control the fan speed (It's quite loud and I'm planning on renting the basement out... with the AC unit right next to the basement window) like those portable AC units? Is this dependent on the thermostat or the AC unit itself? If you're talking about controlling the speed of the fan in the outside condensing unit, the answer is no. The job of this fan, is to remove heat from the refrigerant flowing through the system. Reducing the speed of the fan would reduce the cooling effectiveness of the system, and could lead to damage to, or premature failure of the system. If you're talking about reducing the speed of the blower fan (the fan that circulates air throughout the house), the answer is no again.

The job of this fan is to add heat to the refrigerant flowing through the system. There are numerous instructional videos on how to change the air speed CFM on an airhandler, so YES. Rather than a switch, it is achieved by the wiring. There will be a chart and a wiring diagram on the unit that will direct you. One speed of air does not match all configurations. A specific CFM on a 3 ton unit with a single trunk line feeding a shotgun house might not be the same as a 4 ton unit with a different duct set up, yet the air handler itself might be the same.wooden ac unit coverBrowse other questions tagged air-conditioning thermostat or ask your own question.warranty on ac unit You are here » Room Air Conditionershome ac units explained Variable Air Volume (VAV) is a type of heating, ventilating, and/or air-conditioning (HVAC) system.

Unlike constant air volume (CAV) systems, which supply a constant airflow at a variable temperature, VAV systems vary the airflow at a constant temperature. The advantages of VAV systems over constant-volume systems include more precise temperature control, reduced compressor wear, lower energy consumption by system fans, less fan noise, and additional passive dehumidification. The simplest VAV system incorporates one supply duct that, when in cooling mode, distributes supply air at a constant temperature of approximately 55 °F (13 °C).[1] Because the supply air temperature is constant, the air flow rate must vary to meet the rising and falling heat gains or losses within the thermal zone served. Even a simple VAV system has several advantages over a CAV system. One is more precise temperature control. To meet a space cooling load, a CAV unit operates the fan and compressor at full capacity until the temperature drops to a specified limit, and then the compressor turns off. This on/off cycling causes the temperature to fluctuate above and below the temperature setpoint.

In a single-zone VAV unit, the fan speed varies depending on the actual space temperature and the temperature setpoint, while the compressor modulates the refrigerant flow to maintain a constant supply air temperature. The result is more precise space temperature control. Another advantage is energy savings and reduced wear. VAV fan control, especially with modern electronic variable-speed drives, reduces the energy consumed by fans, which can be a substantial part of the total cooling energy requirements of a building. Modulating control of the compressor also reduces wear and delivers further energy savings. A final advantage is increased dehumidification. Because VAV air flow is reduced under part-load conditions, air is exposed to cooling coils for a longer time. More moisture condenses on the coils, dehumidifying the air. Thus, although a constant-volume and a single-zone VAV unit maintain the same room temperature, the VAV unit provides more passive dehumidification and more comfortable space conditions.

The air blower's flow rate is variable. For a single VAV air handler that serves multiple thermal zones, the flow rate to each zone must be varied as well. A VAV terminal unit,[3] often called a VAV box, is the zone-level flow control device. It is basically a calibrated air damper with an automatic actuator. The VAV terminal unit is connected to either a local or a central control system. Historically, pneumatic control was commonplace, but electronic direct digital control systems are popular especially for mid- to large-size applications.[4] Hybrid control, for example having pneumatic actuators with digital data collection, is popular as well. A common commercial application is shown in the diagram. This VAV system consists of a VAV box, ductwork, and four air terminals. Control of the system's fan capacity is critical in VAV systems. Without proper and rapid flow rate control, the system's ductwork, or its sealing, can easily be damaged by overpressurization. In the cooling mode of operation, as the temperature in the space is satisfied, a VAV box closes to limit the flow of cool air into the space.

As the temperature increases in the space, the box opens to bring the temperature back down. The fan maintains a constant static pressure in the discharge duct regardless of the position of the VAV box. Therefore, as the boxes closes, the fan slows down or restricts the amount of air going into the supply duct. As the boxes open, the fan speeds up and allows more air flow into the duct, maintaining a constant static pressure. One of the challenges for VAV systems is providing adequate temperature control for multiple zones with different environmental conditions, such as an office on the glass perimeter of a building vs. an interior office down the hall. Dual duct systems provide cool air in one duct and warm air in a second duct to provide an appropriate temperature of mixed supply air for any zone. An extra duct, however, is cumbersome and expensive. Reheating the air from a single duct, using electric or hot water heating, is often a more cost-effective solution. ^ a b c d ^ Systems and Equipment volume of the ASHRAE Handbook, ASHRAE, Inc., Atlanta, GA, 2004