Search results
Results from the WOW.Com Content Network
The heating elements activate one at a time to avoid overloading the electrical system. Overheating is prevented by a safety switch called a limit controller or limit switch. This limit controller may shut the furnace off if the blower fails or if something is blocking the air flow.
After the control of air flow and temperature was standardized, the use of electromechanical relays in ladder logic to switch dampers became standardized. Eventually, the relays became electronic switches, as transistors eventually could handle greater current loads. By 1985, pneumatic controls could no longer compete with this new technology ...
Pneumatically actuated shut down valve A diagram of the internal components of a safety shutoff valve. When this type of valve is tripped, the flow is quickly stopped and an indicator disc tells the operator that the electrical circuit has been opened by a failure somewhere in the system.
Industrial pressure switches may have a calibrated scale and pointer to show the set point of the switch. A pressure switch will have a hysteresis, that is, a differential range around its setpoint, known as the switch's deadband, inside which small changes of pressure do not influence the state of the contacts. Some types allow adjustment of ...
The life of a filter may be assessed by monitoring the pressure drop through the filter medium at design air volume flow rate. This may be done by means of a visual display using a pressure gauge, or by a pressure switch linked to an alarm point on the building control system.
This damper can switch the electrical power to control additional "slave" dampers, minimizing the electrical load on the damper's control circuitry and power transformer A zone damper (also known as a Volume Control Damper or VCD ) is a specific type of damper used to control the flow of air in an HVAC heating or cooling system.
Get AOL Mail for FREE! Manage your email like never before with travel, photo & document views. Personalize your inbox with themes & tabs. You've Got Mail!
Reversing valves are built into the heat pump by the manufacturer, and must be replaced by an HVAC technician if they fail. Since the valve is an integral part of the sealed refrigerant circuit, proper procedures for recovering and then later refilling the refrigerant must be followed, to prevent its loss into the atmosphere.