HVAC HVAC Troubleshooting Techniques

Question 1

What is the first step in systematic HVAC troubleshooting?

Accepted Answer

Gather information: verify the complaint, collect operational data, and identify symptoms

Answer

Systematic troubleshooting starts with information gathering — verify the complaint is real, collect operational data (temperatures, pressures, electrical readings), interview the occupant or operator, and identify all symptoms before drawing conclusions.

Question 2

What does high discharge pressure and high suction pressure indicate in a refrigeration system?

Accepted Answer

Overcharge of refrigerant or non-condensables in the system

Answer

Both high discharge and high suction pressures simultaneously suggest overcharge of refrigerant or the presence of non-condensables (air/nitrogen) in the system. Overcharge floods the condenser, raising both pressures. Non-condensables occupy condenser space, raising head pressure.

Question 3

What does low suction pressure AND high suction superheat indicate?

Accepted Answer

Restricted or underfeeding metering device (TXV or orifice)

Answer

Low suction pressure with high superheat indicates the metering device is underfeeding the evaporator — refrigerant is boiling off before filling the coil, leaving superheated vapor. Causes include a stuck TXV, clogged filter-drier, or undercharge.

Question 4

When using a clamp-on ammeter to diagnose an HVAC motor, what does a reading significantly above the nameplate FLA indicate?

Accepted Answer

The motor is mechanically or electrically overloaded

Answer

Current significantly above nameplate Full Load Amperage (FLA) indicates the motor is overloaded. Causes include mechanical overload (seized bearings, blocked fan), electrical problems (low voltage, single-phasing), or a failing motor winding.

Question 5

What does a 'running amperage' that is LOW compared to nameplate FLA typically indicate for a compressor?

Accepted Answer

The compressor has low refrigerant charge, worn valves, or is not fully loaded

Answer

Low running amperage in a compressor can indicate low refrigerant charge (less work being done compressing refrigerant) or worn compressor valves (gas bypasses the pistons, reducing compression work). Either way, the compressor isn't fully loading.

HVAC - Heating, Ventilation, and Air Conditioning Practice Test

HVAC - Heating, Ventilation, and Air Conditioning Practice Test

HVAC HVAC Troubleshooting Techniques