Why Master Heat Pump Service?

Heat pumps are exploding in popularity across the US. Homeowners need technicians who can do more than just change a filter. They need experts in heat pump service, heat pump repair, and advanced troubleshooting.

The NATE Heat Pump Specialty exam is notoriously difficult because it combines electrical logic (defrost boards) with mechanical complexity (reversing valves). Passing this proves you are a top-tier tech.

Interactive Heat Pump Questions

Test your troubleshooting logic.

Question 1
In Cooling mode, the Reversing Valve is usually:
A. De-energized (Rheem/Ruud)
B. Energized (Most brands)
C. Modulating
Click to see answer in App
Question 2
A Time-Temperature defrost board initiates defrost when:
A. Coil temp is low & time elapsed
B. Outdoor air is below 32°F
C. Pressure differential is high
Click to see answer in App

Key Topic 1: The Reversing Valve

The component that defines a heat pump. In heat pump repair service, diagnosing a stuck reversing valve is a critical skill.

4-Way Reversing Valve Operation Diagram
  • O Terminal: Energizes the valve in COOLING (typical for most brands like Carrier, Trane, Lennox). If the wire breaks, it defaults to HEAT.
  • B Terminal: Energizes the valve in HEATING (typical for Rheem, Ruud). If the wire breaks, it defaults to COOL.
  • Diagnosis: A valve is "stuck" if there is a temperature difference greater than 3-5°F across the valve body on the suction side.

Key Topic 2: Defrost Control Logic

Frost on the outdoor coil reduces efficiency. The system must switch to cooling mode momentarily to melt it. Understanding this sequence is vital for heat pump servicing.

Defrost Types:

  • Time-Temperature: The most common. Initiates after a set compressor run-time (e.g., 30, 60, 90 mins) IF the coil sensor is below freezing (approx 30°F).
  • Demand Defrost: Uses sensors to measure air/coil temperature difference or air pressure drop. Only defrosts when ice actually blocks airflow.

Key Topic 3: Auxiliary & Emergency Heat

When it gets too cold (below the "Balance Point"), the heat pump needs help. Electric strips or a gas furnace (Dual Fuel) kick in.

  • Aux Heat: Runs with the heat pump to boost output.
  • Emergency Heat: Manually selected by the thermostat. Locks out the compressor and runs only the backup heat. Used during heat pump repair when the outdoor unit is broken.

Common Heat Pump Questions

What is the Balance Point?

The outdoor temperature where the heat pump's output exactly matches the home's heat loss. Below this, Aux heat is needed.

Why is steam rising from the unit?

This is normal during the Defrost Cycle. The outdoor fan stops, and the coil gets hot to melt ice, turning it into steam.

Is the NATE Heat Pump exam hard?

Yes. It has a high fail rate because it requires understanding complex control wiring and refrigeration cycle reversal.

What is COP?

Coefficient of Performance. It measures efficiency in heating mode. A COP of 3 means it moves 3 units of heat for every 1 unit of electricity.

Explore Other Certifications

NATE Core Service & Install
AC Specialty Air Conditioning
Gas Heating Furnace Prep
EPA 608 Universal License

Ready to Master Heat Pumps?

Our NATE Heat Pump Practice Test covers reversing valves, wiring diagrams, and troubleshooting scenarios.

Start Practice Test