Pool Heat Pump Not Heating? 8 Problems You Can Fix Yourself (Before Calling a Technician)

Before you spend $250 on an emergency service call, take 15 minutes. Eight out of ten broken heat pumps are not actually broken. They are just fighting a problem you can fix yourself. Service calls can cost anywhere from $200 to $400, and technicians are often booked 3 to 5 days out. You need your pool warm now, and the fear that it is a major, expensive problem is likely keeping you from enjoying your morning.

This guide walks you through the 8 most common heat pump problems in order of likelihood. Most take under 10 minutes to check. We will tell you exactly when you do need a professional versus when you just need a screwdriver and some common sense.

We are Arctic Heat Pumps. We have installed over 2,400 pool heat pump systems. These are the actual issues our service techs find on 80% of “not heating” calls. Half the time, homeowners could have fixed them before we even arrived.

How to Know If Your Heat Pump Is Actually Broken

Most of the calls that we receive are related to the heat pump not working. As a matter of fact, my heat pump is not functioning as fast as I had imagined it would. We should establish a base before we explore fixes for what normal operation should look like.

Under good conditions, a healthy pool heat pump should increase the water temperature by 1°F to 1.5 °F per hour. It may require 24 to 72 hours to warm the water in your pool by 20°F, assuming that you have just opened your pool. When the unit is expelling cold air through the top, then that is a good sign. It is an indication that the unit is extracting the heat from the air and transferring it to your water successfully. The condensation of water under the unit should also be observed (in some cases reaching 9 gallons an hour). This is normally confused with a leak, yet it is only a symptom of a working machine.

Signs It Is Not Broken, Just Slow

• The outside temperature is between 50 & 60°F. Heating will be very slow in these conditions.
• The pool temperature has risen even 2 or 3 degrees in the last 24 hours.
• You are trying to heat the pool for the first time this season.

Signs Something Is Actually Wrong

• The unit runs for 24+ hours with zero temperature change.
• The display shows specific error codes.
• The compressor will not start.
• The fan runs, but the compressor remains silent.
• The pool temperature is actually dropping while the unit runs.

Grab a thermometer and run into your pool, and if there is any temperature that has been gained in the last 24 hours, then the unit is operative. It may not be as quick as you want.

Problem #1: Not Enough Water Flow (30% of All Issues)

Heat pumps that are used in pools, are quite sensitive to flow of water. Their usual requirement is 30 to 50 gallons per minute through them. When the amount of water flowing is inadequate, the safety switch is closed by shutting all down so that the unit does not overheat. You may have an FLO on display, or the unit may do nothing at all.

How to Fix It (5 Minute Check)

1. Check Your Pool Water Level: The water is supposed to be centrally located on the skimmer opening. It is too small and thus, the lines are blocked with air. Add water, and repeat after 10 minutes.
2. Check Your Filter Pressure: A clean filter usually shows 8 to 12 PSI. A dirty filter can jump to 18 to 25 PSI. If your pressure is high, backwash or clean your filter. This alone fixes 40% of flow issues.
3. Clear the Baskets: Switch off the pump and pour out the skimmer and pump basket. In this case debris may decrease the flow by 40%.
4. Check the Valves: This sounds obvious, but we find partially closed valves all the time. The pipe is supposed to be aligned with the handle of the valve. Ensure that all the valves between the pool and the heat pump are fully open.
5. Verify the Bypass Valve: There is a possibility of a bypass valve in the installation. When it is open, water cannot pass through your heat pump and can goes around it. When you are heating the pool, the bypass valve should be closed.

When the FLO error continues to occur after such actions, an upgrade of the pump may be required, or a professional may be needed to adjust the flow switch.

Problem #2: It Is Too Cold Outside (25% of Issues)

Here is what salespeople often downplay: pool heat pumps work by extracting heat from the air. When the air is cold, there is less heat to extract. It is physics, not a defect.

Temperature Performance Guide

• 70 to 90°F Outside: Perfect conditions. The unit operates at peak efficiency.
• 55 to 70°F Outside: Functional but patience is required. Heating will be slower.
• 45 to 55°F Outside: The unit will struggle significantly. It might only heat the pool by 0.2°F per hour.
• Below 45°F: The unit may not heat at all and will likely go into “Defrost Mode” to melt ice off the coils.

Having an LP or Low Pressure code usually indicates that the air is too cold to have any refrigerant pressurized correctly. When it was 58°F at 2 PM, but was 38°F overnight, the unit must have been in defrost all night. To run the unit, you can only do it on the sunniest day of the day, or at night, it will need a solar cover to keep the heat you have acquired.

Problem #3: Thermostat Set Wrong (15% of Issues)

We are called out, we come and we see the thermostat at 78°F and already the pool water is at 79°F. The homeowner is bewildered and the bill has not changed to $195 yet. Contrary to the home thermostat, pool heat pumps tend to display the video of the current water temperature as its primary display. The unit becomes hot only when the target temperature is more than the current temperature.

Common Mistakes

• Set Too Low: When the pool temperature is 76°F with the thermostat at 75°F, then it will not come on. Test it with a temperature of 82°F or above.
• Wrong Mode: Make sure that the unit is in heat mode, not cool.
• Sensor Issues: When your display says the water is 72°F, but a floating thermometer indicates that it is 82°F, your sensor could either be dirty or broken.

To check this, put the unit off, turn the thermostat to 85°F , put the mode to HEAT, then turn it on. Wait 5 minutes for the delay of the compressor, and observe whether it starts.

Problem #4: Blocked Airflow (10% of Issues)

Your heat pump needs a massive amount of air to work. It pulls air in by means of its sides and expels cold air through the top. When even the airflow is blocked by half, then your efficiency is halved.

Common Airflow Killers

Check for leaves piled around the unit, overgrown bushes within two feet, or pool toys stored against the machine. The internal evaporator coil should also be checked. When it is plugged with grass cuts or dandelion seeds, it will have a fuzzy or solid appearance.

How to Clean the Coil

Switch off the power at the breaker. Spray inside out with a garden hose that has a nozzle. This provides an outward push instead of an inward push of debris. A pressure washer should never be used, as it will bend the delicate fins.

Problem #5: Electrical Issues (8% of Issues)

With a fully dark display, you probably have a power problem. Check your circuit breaker. It is commonly a 40 to 60 amp double-pole disconnect. In case it is turned on, you have to turn it completely off and then on.

The 5-5-5 Rule: When you use a breaker that you experience 3 trips in 5 minutes, then do not continue resetting it. You have failed short or a failed part. Continued resetting can start a fire.

In case of the smell of something burning or melted wires, call an expert right away. A replacement costs over 2000 dollars to replace a burnt-out compressor due to negligence in terms of electrical conditions.

Problem #6: Refrigerant Leaks (5% of Issues)

Refrigerant is the magic juice that moves heat from the air to your water. Without it, your heat pump is just an expensive fan.

Signs of a Leak

Checking to see whether there is an oily residue below or on the heat pump. If you see a puddle, touch it. The chlorine water in the pools has a smell and the refrigerant is oily and sweet. When the unit is operating continuously and the changes in temperature are not very large or you can hear a hissing sound, then there is most likely a leak. This is not a DIY fix. It requires EPA certification and special tools to repair and recharge.

Problem #7: Dirty Pool or Chemical Imbalance (5% of Issues)

The elevated calcium level may lead to scaling on the inside of a heat exchanger. This scale insulates and prevents the heat from your water from getting to your unit, and this makes the unit 30 percent to 50 percent less efficient. Equally, low PH (less than 7.2) may corrode the metal parts, resulting in micro-leaks. Maintain the balance of your water (pH 7.4-7.6) in order to have your heater last 10 to 12 years.

Problem #8: Component Failure

Sometimes, parts just wear out. The most common (and the cheapest) professional repair is a failed capacitor. In the event that the unit is clicking but the compressor is not starting, then the capacitor is probably the suspect. When the compressor of the heat pump is more than 10 years old and fails, then it is generally more appropriate to change the entire unit instead of paying $1,500 to repair it.

The 15 Minute Troubleshooting Checklist

Before calling for service, check these in order:

• Step 1: Water Flow: Is the water level correct? Is the filter pressure under 15 PSI? Are the baskets clean?
• Step 2: Thermostat: Is it in HEAT mode? Is the target temp set 5 degrees above the current temp?
• Step 3: Electrical: Is the breaker ON? Does the display have power?
• Step 4: Airflow: Is the unit clear of debris and bushes?
• Step 5: Environment: Is the outside temperature above 50°F?
• Step 6: Reset: Turn it off for 5 minutes, turn it back on, and wait for the compressor delay.

Conclusion

The trend is quite obvious. 80 percent of the heat pump issues in pools are maintenance or operator-related. Actual equipment failures are only 20%. Take 15 minutes and fill in this checklist prior to service. You will either do it yourself or provide the tech with useful information that will save you money, as it will accelerate their diagnosis.

Provided that your heat pump is less than 3 years old, and nothing on this list worked, then call in to have it fixed under warranty. When the vehicle is 10 years or above and requires a significant component, it may be necessary to go out to purchase a new and more efficient model.