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  2. Is It Time for a Furnace Upgrade? 10 Warning Signs to ... - AOL

    www.aol.com/time-furnace-upgrade-10-warning...

    Typically, a furnace will last about 15 to 20 years if it's properly maintained and repaired whenever a problem arises. In some cases, a furnace might last up to 30 years, though it's more likely ...

  3. Physics of whistles - Wikipedia

    en.wikipedia.org/wiki/Physics_of_whistles

    Instability of laminar jets Unstable water jet. Flow instability is the engine for whistles. It converts steady energy to time-dependent energy. An example is shown in the figure on the right with a water jet. [3] The laminar two-dimensional jet amplifies small disturbances at the orifice to generate a vortex street. For this case, the flow ...

  4. Mercury switch - Wikipedia

    en.wikipedia.org/wiki/Mercury_switch

    A mercury switch is an electrical switch that opens and closes a circuit when a small amount of the liquid metal mercury connects metal electrodes to close the circuit. There are several different basic designs (tilt, displacement, radial, etc.) but they all share the common design strength of non-eroding switch contacts.

  5. Thermostat - Wikipedia

    en.wikipedia.org/wiki/Thermostat

    Wait (if furnace is relatively recent) until the heat exchanger is at proper operating temperature before starting main blower fan or circulator pump; Oil Similar to gas, except rather than opening a valve, the furnace will start an oil pump to inject oil into the burner Electric

  6. Thermosiphon - Wikipedia

    en.wikipedia.org/wiki/Thermosiphon

    Thermosyphon circulation in a simple solar water heater (not a working model; there is no water supply to replenish the tank when the tap is used). A thermosiphon (or thermosyphon) is a device that employs a method of passive heat exchange based on natural convection, which circulates a fluid without the necessity of a mechanical pump.

  7. Furnace (central heating) - Wikipedia

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

    A two-stage furnace has to do two stage full speed and half (or reduced) speed. Depending on the demanded heat, they can run at a lower speed most of the time. They can be quieter, move the air at less velocity, and will better keep the desired temperature in the house.

  8. Heating, ventilation, and air conditioning - Wikipedia

    en.wikipedia.org/wiki/Heating,_ventilation,_and...

    Most modern hot water boiler heating systems have a circulator, which is a pump, to move hot water through the distribution system (as opposed to older gravity-fed systems). The heat can be transferred to the surrounding air using radiators, hot water coils (hydro-air), or other heat exchangers. The radiators may be mounted on walls or ...

  9. Reversing valve - Wikipedia

    en.wikipedia.org/wiki/Reversing_valve

    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.