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UNIT 52 REVIEW QUESTIONS ANSWER KEY GO BACK TO INDEX
52-1) List the four areas of an electronic control board that should be identified when
troubleshooting.
52-2) What is a typical high limit cut out temperature?
52-3) A given transformer has a primary voltage of 240 V and a secondary voltage of
24 V. Assuming the transformer is rated at 40 VA, what is the secondary
current?
52-4) What is the standard transformer VA rating for most HVAC systems?
52-5) Why are heat anticipators used in low voltage thermostats?
52-6) How do electronic thermostats control system cycling?
52-7) List the types of direct acting gas valves.
52-8) Explain the reason why adding humidity to a residence increases customer
comfort.
52-9) On a fan/limit switch what is the usual setting for the limit?
52-10) List the four functions of a furnace gas valve.
52-11) What is a redundant gas valve?
52-12) How many volts are generated in the spark ignition circuit?
52-13) Why is it necessary that the gas burning unit be grounded on DS1system?
52-14) On a DSI ignition system if a burner fails to light or the flame sensor fails
to detect a flame, what happens to assure the system is safe?
52-15) Describe the operation of a diaphragm gas valve.
52-16) How does a hot surface ignition system work?
52-17) Describe how flame rectification works.
The flame rectification circuit looks for the presence of flame. If flame is sensed,
the gas valve remains energized and the igniter is de-energized. If flame is not
52-18) List the 5 major electrical devices in the heating circuit diagram in Figure 52-
30.
52-19) Explain what a limit switch is, as well as its function and how it affects the
control circuit.
52-20) State why the legend and the notes are an important part of an electrical
diagram.
