Duct Temperature Sensor - The duct static temperature sensor measures air temperature in the ductwork. The solid-state temperature sensing devices are commonly used in HVAC applications that are controlled by direct digital control or a modern building automation system. At the base of the box is a probe that sticks into the air stream of the ductwork. As the air passes over it, the probe changes resistance. (more…)
Heat Pump Electric Backup Heating Basics. There are different types of electric heating available in homes. Probably the most common use for electric heat other than portable electric heating units is electric heat strips. Electric heat strips used for backup heat in heat pumps. Sizing the electric heat strips for heat pump backup heating applications will depend on many different variables.
These variables include the size of the space to be heated and the insulation values of the whole structure. It also includes doors and windows. Additionally, it includes the geographical location of the dwelling, along with many other factors. Backup heat for heat pumps is essential for the defrost cycle. (more…)
The TXV or Thermostatic Expansion Valve is preferred over other refrigeration metering devices because it only allows a specified amount of refrigerant to flow based on demand. Any type of refrigeration metering device creates a pressure drop in the refrigerant and with a pressure drop of the refrigerant a temperature drop also occurs.
This temperature is necessary to drop the refrigerant down to temperature lower than ambient temperatures inside the structure being cooled. This allows the refrigerant to absorb the heat contained in the air passing over the evaporator coil. (more…)
Heat Exchanger & Domestic Hot Water Storage Tank
Heat Exchanger & Domestic Hot Water Storage Tank - In the front is a commercial heat exchanger. Behind the commercial heat exchanger is a domestic hot water storage tank.
The entire system is monitored by direct digital controllers to control the water temperature, the boilers, the valve actuators, and the heat exchangers. It is important to monitor the temperature of any domestic water system. Temperatures above 130° F. should be avoided as they will scald people. This can result in legal issues so it is important this is controlled accurately. Direct Digital Control can offers alarms for this issue in case something goes wrong or something fails.
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