Is it geothermal or air-source?
A geothermal (ground-source or water-source) heat pump exchanges heat with the ground or a water source through buried piping called a ground loop. An air-source heat pump uses an outdoor unit with a fan and coil. A quick clue: if there is no outdoor fan unit and instead a unit sits indoors, in a basement or utility room, with pipes running to the ground, it is likely geothermal. Check your paperwork or the nameplate, or ask your installer, if you are unsure.
Because the ground stays at a relatively steady temperature, geothermal systems are less affected by outdoor air than air-source ones. Many of the basic operating questions, however, are the same, so our guide on whether a heat pump should run all the time applies as well.
Safe checks before you call
These are things most homeowners can do:
- Check the thermostat: correct mode, setpoint, and batteries if applicable.
- Check the air filter: replace it if dirty. A clogged filter is a common cause of poor performance.
- Check vents and returns: open and unblocked.
- Check the breaker: if it has tripped once, you can reset it one time, but only if there is no burning smell, water, or sparking. If it trips again, leave it off and call a technician.
- Look for water: note any leaks around the unit or condensate drain, and shut off the unit if there is water near electrical parts.
- Note any display codes or lockout messages and write them down for the technician.
Do not open electrical panels, handle refrigerant, or work on the ground loop yourself.
Why a geothermal unit may not cool
- Dirty filter or restricted airflow. The checks in our heat pump won’t cool guide apply here too.
- Thermostat settings or a faulty thermostat. See heat pump thermostat not working.
- Ground loop problems, such as low flow, air in the loop, or loop temperatures out of range.
- Low refrigerant or a refrigerant leak. Refrigerant work requires certified technicians.
- Compressor trouble.
- Blower motor or reversing valve problems.
- Not keeping up on the hottest days, which may mean a sizing or loop capacity issue.
If air from the vents is only slightly cooler than the room, or the unit shuts down and restarts repeatedly, switch it off and call a technician.
Why it may not heat well
Many causes overlap with cooling: filter, thermostat, airflow and loop problems. In heating mode, a loop that is too cold, a stuck reversing valve, or an electrical fault can all reduce output. Backup electric heat may be running more than usual, which raises bills. See when to use emergency heat for how backup heat is meant to be used.
Ground loop and pump problems
Typical loop concerns include leaks, corrosion, pump failure, air or contamination in the loop fluid, and damaged buried piping. Symptoms can include low pressure readings, pump noise, frequent lockouts, or a puddle in the yard where the loop runs. These systems may contain antifreeze or other additives, and loops are pressurized. Diagnosis and repair should be left to a technician familiar with geothermal systems.
Noises, lockouts and error codes
Sounds such as grinding, banging or loud humming warrant switching the unit off. A lockout (a safety shutdown) is the system protecting itself, often from high or low pressure or temperature. Repeatedly resetting it can hide a serious fault, so note the code and call a technician rather than resetting over and over.
Can geothermal run out?
The ground is not a fuel supply that gets used up. The system moves heat to and from the earth, and a properly designed loop is intended to last for decades. Problems tend to come from an undersized or poorly designed loop, a damaged loop, or heavy long-term imbalance between heating and cooling loads, rather than the ground running out of heat. If you think your loop is underperforming, a technician can check the loop temperatures.
Disadvantages to know
- Higher upfront installation cost than air-source systems.
- Installation involves drilling or digging, which can disrupt a yard.
- Repairs to buried loops can be expensive and disruptive.
- Fewer technicians are trained to service geothermal compared with conventional systems.
Many owners still find the lower running costs worthwhile. These are general points; your situation may differ.
When to call a professional
Call a qualified geothermal or HVAC technician when:
- The unit does not cool or heat after the basic checks.
- Breakers trip repeatedly, or there are burning smells.
- You see leaks, or suspect refrigerant or loop fluid problems.
- The system locks out or shows repeated fault codes.
- The pump or compressor is making unusual noises.
Turn the power off at the breaker if you see water near electrical parts or smell burning, and keep others away until a professional has inspected it.
Related operation questions
If your concern is about fan settings, see heat pump fan: on or auto. If a thermostat message reads Recovery, see heat pump recovery mode.