Heat Pump Basics

Heat Pump Basics

Heat pumps are a popular way of heating a pool. Heat pumps are energy efficient and can be installed anywhere a 20 to 60 amp electrical circuit is available depending on the BTU output.

The major pool equipment manufacturers all sell heat pumps - Pentair with the UltraTemp, Jandy with the VersaTemp JRT Series, Hayward with various models. There are also good heat pumps manufactured by independent companies - RayPak_Heaters#Raypak_Heat_Pumps Raypak, Aquacal, Gulfstream, Built Right (acquired by Fluidra), and others.

There is little difference in the heat pump technology used by manufacturers as they all use the similar parts from other manufacturers for many components including compressor and electronics. What does differ between manufacturers is the warranty and service, controls, and pool automation communication.

Heat Pump Selection Considerations

Things you need to consider in choosing a heat pump are:

• Warranty and Support - many companies that sell heat pumps do not service them. Inquire who locally will provide warranty service and after warranty service. Members have found they had orphan heat pumps with no one locally who can fix a problem. Any service that touches the refrigerant requires a technician with an Section 608 EPA Techncian Certificate.
• BTU (Heat) Output for your size pool - the largest heat pumps put out 130,0,000 to 140,000 BTUs. A 140K heat pump typically requires a 240 volt/50 amp circuit. A smaller heat pump may require a smaller electrical circuit.
  • Pentair has a Heat Pump Calculator to determine the appropriate size Heat Pump for your location. Pentair seems to do honest calculations based on the physics and efficiencies of each type of pump and energy source.
  • Raypak also has a Heat Pump Heater Sizing App.
  • Aquacal has a Heat Pump Sizing and Savings Calculator.
  • To get the most accurate cost comparison you should change the default electric kwh, natural gas price, and propane price to actual prices in your area.
• Automation Compatibility - if you have a pool automation panel then you want your heat pump to communicate with it. All heat pumps can be controlled by a 2-wire control. Some heaters can be controlled by RS-485 digital communications with the automation. Usually RS-485 comm requires the automation and heat pump to be from the same manufacturer.
• Cooling capability - Some heat pumps can both heat a pool or cool a pool. Cooling a pool using a heat pump may not be the most energy efficient way. Other methods to cool a pool are discussed in Cooling A Pool. For automation to automatically switch between HEAT mode and CHILLER mode requires RS-485 communication and even then it can be glitchy. Research this area carefully and ask on the Forum with your pool details if this is important to you.

Heat Pump Operation

Heat pumps operate by taking heat from the surrounding air and transferring it into the water. The warmer the air and the more humidity in the air, the more latent heat is available for heating your pool.Depending on the sized heat pump for your pool volume, the heat pump can raise your pool 1/2°F to 2°F per hour depending on air temperature, humidity, and water temperature.

For example, a 140,000 BTU heat pump can raise a 17,000 gallon pool about 1°F per hour. A smaller BTU heat pump will raise the temperature less as will a larger pool.

The ideal or rated condition for the heat pump is 80°F air temperature, 80% relative humidity, and 80°F water temperature. As conditions decrease from 80/80/80, the heat pump performance will decrease.

Heat Pumps are best utilized to maintain a set water temperature; they are not intended to provide instant or fast heating. It is not reasonable to expect a heat pump to perform like a gas heater which has a much higher BTU output and faster response. Additionally, gas heaters are not dependent on environmental conditions.

Proper operation and use of the heat pump is to set it at your desired temperature and leave it with your pool pump running. Your heat pump will turn on and off automatically to maintain your desired temperature much like your home HVAC unit.

To take advantage of the sun’s energy, operate your heat pump during the heat of the day. Your heat pump will still operate when the temperature drops at night, but the output will be decreased. It is acceptable to shut the heat pump off and not use it for extended periods of time.

Using a pool cover with a heat pump will minimize the pool waters heat loss and reduce the heat pump runtime which will save on your electrical bill.

When you have a need to heat your pool, you must plan accordingly since it may take the heat pump days to heat your pool back to your desired temperature, depending on your pool temperature and environmental conditions.

Heat Pump Preventative Maintenance

Manufacturers recommend that you inspect your heat pump on a continual basis and especially after abnormal weather conditions. The following basic guidelines are suggested for your inspection:

1. Make sure the front of the unit is accessible for future service.
2. Keep the top and surrounding areas of the heat pump clear of all debris.
3. Keep all plants and shrubs trimmed and away from the heat pump.
4. Keep lawn sprinkler heads from spraying on the heat pump to prevent corrosion and damage.
5. If the unit is installed under a roof edge, install a gutter or diverter to prevent excessive water and debris from pouring down into the unit.
6. Do not use this heat pump if any part has been under water. Immediately call a qualified professional technician to inspect the heat pump and replace any part of the control system which has been submerged.
7. If your HP has a condensate drain visually inspect and clear the bottom drain ports of any debris that could clog the ports.
8. Keep the air flow discharge and air flow intake area clear of debris so the air flow though the heat pump is not restricted. The cooler discharge air should not accumulate and be drawn into the intake coils.
9. Keep the air coil clean from dirt and debris. It is recommended to clean your air coil once a year by flushing the coil with compressed air or hosing off the coil with a garden hose.
10. Care should be taken to not bend the coil fins as this will restrict the airflow and lower your heat pump performance. Compressed air can also damage the heat pump coil. DO NOT USE A PRESSURE CLEANER ON THE UNIT.

Common Heat Pump Problems

The most common problem is the fan at the top of the heat pump is turning and you are getting no heat. The lack of heat is because the compressor is not running. The usual cause is a failed compressor start capacitor. Another reason can be a failed contactor that powers the compressor. Other less likely reasons can be the compressor failed or there is a lack of refrigerant.

Note that heat pumps have a 5 minute safety delay between cycling the compressor. So it may take 5 minutes after heat is requested for the compressor to turn on and heat being generated.

If the fan on the top of the heat pump is not turning then check the HP circuit breaker. Obviously check that the HP is turned on and the set temperature is greater than the water temperature. If there is electrical power and the the HP is on the fan motor may have failed.

Heat pumps need the correct refrigerant level. It is common for refrigerant to leak out over time and eventually trigger an error. Low refrigerant can trigger low pressure or high pressure error codes.