Heat pump parts: what each one does
Knowing the main parts helps you describe a problem clearly to a technician. It does not mean you should open anything.
A heat pump has a short list of major parts, split between the outdoor unit and the indoor unit. Together they move heat instead of making it. Learning the names helps you read a repair quote and explain a symptom, but nearly all of these parts are for a licensed technician only.
The main parts of a heat pump
Every system uses the same basic set. Some sit outside, some inside, and a few sit in between.
| Part | Where it is | What it does |
|---|---|---|
| Compressor | Outdoor unit | Pressurizes refrigerant so heat can move |
| Reversing valve | Outdoor unit | Flips the flow between heating and cooling |
| Outdoor coil | Outdoor unit | Takes heat from the air or releases it |
| Outdoor fan | Outdoor unit | Pulls air across the outdoor coil |
| Indoor coil | Air handler | Swaps heat with the air in your ducts |
| Blower | Air handler | Pushes the conditioned air through the house |
| Expansion device | Between coils | Meters refrigerant into the indoor coil |
| Thermostat | On your wall | Tells the system what to do |
The reversing valve is what makes it a heat pump
An air conditioner only moves heat out of your house. A heat pump can run the same cycle backward, and the reversing valve does that. When it sticks, you may get cool air in winter or no change in temperature at all. It is a sealed refrigerant part, so it is never a DIY job.
Parts you can safely see and care for
Only a few items are yours to handle. The air filter is the big one. Replace it on schedule. The outdoor coil and fan cabinet can be kept clear of leaves, grass and snow by hand. The thermostat is also fair game: check its mode, its setpoint and its batteries.
Everything else, including the compressor, the valve and the wiring, stays closed.
Which part fails first?
It depends on the system, but the usual suspects are not the expensive ones. Dirty filters, weak thermostat batteries and clogged coils cause more service calls than a dead compressor. Electrical parts such as contactors and capacitors also wear out. Do not test or open a capacitor yourself, because it can hold a dangerous charge even with the power off.
What not to do
- Do not remove panels on the outdoor unit or touch wiring inside.
- Do not add or remove refrigerant. Federal law requires EPA Section 608 certification to handle it.
- Do not buy a part online and try to fit it. Parts are matched to your model.
Our advice: learn the names, then hand it off
Use this list to describe what you see and hear. Say which unit it comes from, what changed and when. A licensed HVAC technician can then bring the right part and skip the guesswork.
Frequently asked questions
What are the main parts of a heat pump?
The compressor, reversing valve, outdoor coil and fan, indoor coil, blower, expansion device and thermostat. They work together to move heat in or out of your home.
What does the reversing valve do in a heat pump?
It switches the direction of refrigerant flow so the same system can heat in winter and cool in summer. If it sticks, the unit may blow the wrong temperature of air.
Which heat pump parts can I take care of myself?
You can replace the air filter, keep the outdoor unit clear of debris and check the thermostat settings and batteries. Everything involving refrigerant or wiring needs a licensed technician.
Sources
What this page explains is based on these official sources. If you check one and it does not match what you read here, send it to us and the article gets corrected.
- ENERGY STAR. Air-Source Heat Pumps
- ENERGY STAR. Energy Savings at Home: Heating & Cooling