Heating unit 31

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  1. Sequence of operation of a gas furnace
    • Thermostat call for heat
    • 24v signal is sent to open gas valve
    • gas is delivered into the manifold, pilot must be lit to ignite the gas
    • the burners will heat up the heat exchanger
    • the blower fan will energize when the heat exchanger reaches 150*
    • the system de-energizes when the thermostat is satisfied, the blower will continue to run until the heat exchanger cools to 110*
  2. what is the gas pressure of natural gas in a single stage gas valve
    double stage (1 & 2)
    • 3.5" WC
    • 1.7" WC
    • 3.5" WC
  3. Pilot light that is only turned on during the on cycle of the furnace is callled
    an intermittent pilot ignition
  4. the orifice is a precisely size hole in the
  5. the spud is where, and does what
    in the manifold, sends fuel to the burner
  6. a flame sensing rod should read above 1
    • uA D/C or 
    • microamps
  7. the limit switch is a safety switch that does what
    closes the gas valve if the furnace over heats
  8. the pressure switch is a safety device that
    • shuts off the system if the flue gets clogged
    • keeps the system from running if the draft inducer is bad
  9. air that mixes with combustion by-products after combustion at the beginning of the flue pipe is
    dilution- air
  10. a direct spark ignition is designed to.
    provide ignition to the main burners
  11. propane manifold pressure should be
    10" of WC
  12. combustion is sometimes expressed as
    rapid oxidation
  13. natural gas is composed of 90- 95% of
  14. conventional furnaces vent their gases how
    natural  convection
  15. a furnace that has a sealed combustion chamber and for which combustion air comes from outside the conditioned space is a
    direct-vent furnace, (high eff)
  16. a small microprocessor with integrated circuits mounted on a board to control the logic or sequence of the events of the furnace is a
    integrated furnace controller
  17. the dangerous by- product of poor combustion of gas is
    carbon monoxide
  18. three products of complete combustion of natural or LP gas
    • carbon-dioxide
    • water vapor
    • heat
  19. a furnace with a vertical air flow through the heat ex-changer and the blower compartment beneath the heat ex-changer is called an
  20. a condensing gas furnace uses_____from a condensing type heat ex-changer to increase the furnace efficiency
    latent heat
  21. a thermocoupler is used in a conventional gas furnace as a
    flame proving device
  22. spark ignition is important for roof top or package units located outdoors because of ____________problems
  23. the proper color of a gas flame is
    blue with orange tips
  24. natural gas is _______than air
  25. liquid petroleum is ______than air and can cause suffocation if not handled properly
  26. what does a manometer measure
    gas pressure
  27. it take _______cubic ft of air to produce 2 cubic ft of oxygen to mix with 1 cubic ft of  natural gas to produce 1050 btu when burned
    10 cubic ft of air
  28. a standing pilot lights how
    continuously burns
Card Set
Heating unit 31
sequence of operation, furnaces, efficiency,
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