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2. Central heating - Wikipedia

   en.wikipedia.org/wiki/Central_heating

   An expansion tank contains compressed gas, separated from the sealed-system water by a diaphragm. This allows for normal variations of pressure in the system. A safety valve allows water to escape from the system when pressure becomes too high, and a valve can open to replenish water from the normal water supply if the pressure drops too low ...

3. Furnace (central heating) - Wikipedia

   en.wikipedia.org/wiki/Furnace_(central_heating)

   The fourth category of furnace is the high-efficiency condensing gas furnace. High efficiency condensing gas furnaces typically achieve between 90% and 98% AFUE. [3] A condensing gas furnace includes a sealed combustion area, combustion draft inducer and a secondary heat exchanger. The primary gain in efficiency for a condensing gas furnace, as ...

4. HVAC control system - Wikipedia

   en.wikipedia.org/wiki/HVAC_control_system

   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 ...

5. Forced-air - Wikipedia

   en.wikipedia.org/wiki/Forced-air

   [2] [3] It is the design of this mechanism that determines the accuracy of maintaining the set flow rate, noise level, minimum regulator resistance, flow range and other parameters. [ 4 ] [ 5 ] There are different designs of the self-balancing mechanism that largely determine the technical characteristics of CAV regulators:

6. Pressure switch - Wikipedia

   en.wikipedia.org/wiki/Pressure_switch

   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 ...

7. Pilot light - Wikipedia

   en.wikipedia.org/wiki/Pilot_light

   In natural gas furnaces, water heaters, and room heating systems, a safety cut-off switch is normally included so that the gas supply to the pilot and heating system is shut off by an electrically operated valve if the pilot light goes out. This cut-off switch usually detects the pilot light in one of several ways: A flame rectification device. [2]