NATE gas heating service and installation practice test
165 free practice questions for this exam, each with the reason for the answer and where to look it up.
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HVAC service and troubleshooting: practice test
10 questions, graded as you go, with the reason for every answer. No sign-up.
Question count, time limit and pass mark differ by where you take it. Check the official candidate bulletin from the organisation that runs your exam.
Sample questions
A furnace's rating plate lists a maximum external static pressure of 0.50 in. w.c. The measured total external static pressure is 0.95 in. w.c. What does this tell the technician?
The blower is moving more air than the duct was designed for
The duct system is too restrictive and airflow is below design
The furnace is operating normally within its allowable range
The supply ducts are leaking and losing pressure to the attic space
Show the answer
B. The duct system is too restrictive and airflow is below design
Static pressure is the resistance the blower works against. Nearly double the rated maximum means undersized or blocked ducts, a restrictive filter or a dirty coil, and with a PSC blower airflow falls well below design. Leaky ducts lower static pressure rather than raise it.
Reference: Total external static pressure; blower performance
Why are gas burners set up with more air than the exact amount needed for complete combustion?
To raise the temperature of the burner flame as high as possible
To increase the carbon dioxide percentage in the flue gas
To keep the flue gas from rising too quickly in the vent
To make sure all the fuel finds oxygen and burns completely
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D. To make sure all the fuel finds oxygen and burns completely
Mixing in a real burner is never perfect, so some excess air is supplied as a safety margin against carbon monoxide. It comes at a cost: extra air carries heat up the vent and lowers the flame temperature, so too much of it reduces efficiency.
Reference: Combustion fundamentals; excess air
The blower will not run when the thermostat's fan switch is set to On. Jumpering R to G at the air handler's terminal strip starts the blower. Where is the fault?
In the blower motor or its run capacitor
In the thermostat or the G conductor of the cable
In the air handler's blower relay or board
In the control transformer's secondary winding
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B. In the thermostat or the G conductor of the cable
The jumper proves that everything from the G terminal onward, including the relay and motor, works when it receives 24 V. The signal is therefore not arriving, so the thermostat's fan contact or the G wire between thermostat and air handler is open.
Reference: Thermostat troubleshooting; fan circuit
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