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2. Pressure switch - Wikipedia

   en.wikipedia.org/wiki/Pressure_switch

   Switch enclosures may also be required to be weatherproof, corrosion resistant, or submersible. An electronic pressure switch incorporates some variety of pressure transducer (strain gauge, capacitive element, or other) and an internal circuit to compare the measured pressure to a set point. Such devices may provide improved repeatability ...

3. Central heating - Wikipedia

   en.wikipedia.org/wiki/Central_heating

   Details of furnace and expansion tube from Perkins' 1838 Patent. Perkins' 1832 apparatus distributed water at 200 degrees Celsius (392 °F) through small diameter pipes at high pressure. A crucial invention to make the system viable was the thread screwed joint, that allowed the joint between the pipes to bear a similar pressure to the pipe itself.

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. Thermal expansion valve - Wikipedia

   en.wikipedia.org/wiki/Thermal_expansion_valve

   The refrigerant is compressed by the compressor to a high-pressure and high-temperature gaseous state. The high-pressure and high-temperature gas then enters the condenser. The condenser cools the high-pressure and high-temperature gas allowing it to condense to a high-pressure liquid by transferring heat to a lower temperature medium, usually ...

6. 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 ...

7. Thermostat - Wikipedia

   en.wikipedia.org/wiki/Thermostat

   Start draft inducer fan/blower (if the furnace is relatively recent) to create a column of air flowing up the chimney; Heat ignitor or start spark-ignition system; Open gas valve to ignite main burners; Wait (if furnace is relatively recent) until the heat exchanger is at proper operating temperature before starting main blower fan or ...