HVAC Troubleshooting 5

Question 1

An air conditioning system has normal suction pressure but very high discharge pressure. Outdoor ambient temperature is 85°F. What is the most probable cause?

Accepted Answer

Dirty or blocked condenser coil

Answer

A dirty or blocked condenser coil restricts airflow and reduces heat rejection, causing discharge pressure to rise well above normal for the ambient temperature.

Question 2

A technician notices that a system's compressor trips on its internal overload protector repeatedly. Amp draw is below nameplate. What should be suspected?

Accepted Answer

High ambient temperature around the compressor

Answer

Even with normal amperage, excessive ambient temperature around the compressor can cause the thermal overload to trip as the compressor overheats.

Question 3

A ductless mini-split displays an error code and the outdoor unit produces a grinding noise. What is the most likely component causing the noise?

Accepted Answer

Outdoor fan motor bearings

Answer

Worn or failing fan motor bearings produce a grinding noise in the outdoor unit and may trigger a fault code due to reduced or erratic fan speed.

Question 4

A technician finds that a boiler is not firing even though the thermostat is calling for heat. The system has 24V at the thermostat. What should be checked next?

Accepted Answer

Low water cutoff device

Answer

A low water cutoff (LWCO) shuts down the burner when water level or pressure is insufficient, and is a common safety-related cause of a boiler not firing.

Question 5

After startup in the spring, a split system produces adequate cooling but has a musty odor. What is the most appropriate corrective action?

Accepted Answer

Clean evaporator coil and condensate drain with appropriate cleaner and biocide

Answer

Musty odors from HVAC systems are caused by mold and bacterial growth on the wet evaporator coil and in the condensate drain, requiring cleaning and biocide treatment.

HVAC Practice Test

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HVAC Troubleshooting 5