Outside Air Temperature-Humidity Sensor Outside Air Temperature-Humidity Sensor  - The outside air temperature sensor uses a thermistor to read the outside temperature. This sensor also senses humidity using a humidity transducer. The temperature and humidity readings are collected by a direct digital control system and used in a program. Aside from using this information for user interfaces, the information is also used in a control program to open and close an outside air damper. 

Outside Air Temperature-Humidity Sensor

Even when temperatures outside are mild the inside of buildings need cooling. The air conditioner can handle cooling the building just fine. However, there are times when running the air conditioner is unnecessary when the temperature of the outside air is ideal. Engineers have designed systems to include ductwork that leads outside. Inside this duct is a damper which leaves the system closed off to the outside unit the control system calls for the damper to open. This is often referred to as an airside economizer or free cooling. These systems are designed to meet code requirements and offer free cooling economizing.

The control systems open the outside air damper based on outside air temperature and humidity. At the same time, the control program locks out mechanical cooling so the air conditioner does not run when the program opens the outside air damper. This saves energy and reduces the cost of air conditioning when the temperature and humidity outside are ideal for conditioning the building.

 Outside Air Temperature-Humidity Sensor | Pros and Cons

The Pros of having such a system are stated above with the energy efficiency the system adds and the information it provides to the end-user. What are the cons of having such a system? Of course with any type of system you are going to have maintenance and with the temperature, you are okay with the maintenance because a 10K thermistor requires very little maintenance, however, the humidity sensor does require periodic replacement and calibration to be effective and functional in the system.

Economizing and Free Cooling | Saving Energy and Meeting Code | Outside Air Temperature-Humidity Sensor

Airside economizers are used year-round by air handlers to comply with ventilation requirements of codebooks including the mechanical code. Specific types of commercial buildings require so many changes of air per hour. To comply with the code, airside economizers are used for satisfying the code. An additional program can be used for free cooling when outside temperature/humidity conditions meet specific parameters within the program. This locks out mechanical cooling and uses the outside air for cooling. That alone saves energy by utilizing ideal conditions outdoors rather than burning electricity to run compressors for mechanical cooling.

Outside Air Temperature-Humidity Sensor Maintenance

It is important that the Outside Air Temperature-Humidity Sensor be checked for accuracy from time to time. Installation location is also important. It should be placed under a soffit out of direct sunlight on the north side of the building for accuracy. Maintenance checks include calibration and sometimes replacing the sensors to meet specific calibration requirements. At the time of this writing typical longevity of the humidity sensor is approximately 2 years.

Therefore, on scheduled maintenance bi-annually, the humidity sensor should be replaced to prevent failure of the device. If the device fails, it can result in extra electricity costs from the utility. The temperature sensor typically lasts indefinitely.

Once every few years, the humidity sensor needs to be replaced. An alternative to that is to have the system pull in the humidity data from the local TV or weather station. I know it can be done without compromising security.

Outside Air Temperature-Humidity Sensor

High Performance HVAC

Outside Air Temperature-Humidity Sensor