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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. 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:

  5. Forced-air gas - Wikipedia

    en.wikipedia.org/wiki/Forced-air_gas

    Older furnaces sometimes relied on gravity instead of a blower to circulate air. [1]Gas-fired forced-air furnaces have a burner in the furnace fueled by natural gas.A blower forces cold air through a heat exchanger and then through duct-work that distributes the hot air through the building. [2]

  6. Distributed control system - Wikipedia

    en.wikipedia.org/wiki/Distributed_control_system

    A typical application is a PID controller fed by a flow meter and using a control valve as the final control element. The DCS sends the setpoint required by the process to the controller which instructs a valve to operate so that the process reaches and stays at the desired setpoint. (see 4–20 mA schematic for example).

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