How to set up a pool heat pump

A heat pump is the cheapest way to keep a pool warm in mild weather, but only if it's sized for your climate and has room to breathe. Most "my heat pump won't heat" calls come down to one of three things: blocked airflow, the wrong size, or not enough run time. This guide covers all three, plus the electrical and plumbing details.

How a pool heat pump works

A heat pump doesn't burn anything. It pulls heat out of the outside air and moves it into your water, like an air conditioner running in reverse. At mild temperatures, a good unit delivers about 5–6 units of heat for every unit of electricity it uses (called its COP). Efficiency drops as the air gets colder, which is why climate matters so much when you size one.

Is a heat pump right for your climate?

Most standard heat pumps work best when the air is above about 50°F. Output falls off as the air cools, and models without a defrost feature can stop heating in cold weather.

Too hot in August? Heat/cool models can also chill your water when it climbs past 90°F in a Texas summer. See our pool chillers for dedicated cooling.

Sizing a pool heat pump

Read the rating conditions

Many brands advertise BTU output at "80/80/80" conditions: 80°F air, 80% humidity and 80°F water. That's close to a best case. When comparing models, look for the rating at 50°F air too, which is a better guide for spring and fall.

Typical sizes

These are starting points. Size up if the pool is uncovered, windy or shaded, has an attached spa or large water features, sits in a colder part of the state, or you want faster recovery. An oversized heat pump isn't less efficient. It just reaches your target sooner.

Set realistic expectations

Raising 20,000 gallons by 1°F takes about 166,800 BTUs. A heat pump putting out 110,000 BTU/hr adds roughly two-thirds of a degree per hour before heat loss. That means a first heat-up can take a day or more. Heat pumps are built to hold temperature, not to heat quickly. A solar cover cuts evaporation, the biggest source of heat loss, and makes a big difference.

Get your gallons with our pool calculator.

Placement and airflow clearance

A heat pump that recirculates its own cold exhaust air loses efficiency. Your manual lists exact clearances. Typical requirements look like this:

• Air intake sides: Open space on every side the coil draws air through, commonly a foot or more.
• Service side: Enough room to remove panels and reach the controls, often about 2 ft.
• Above the fan: Top-discharge units need several feet of open space overhead (5 ft is common). No roofs, decks or dense tree canopy.
• No boxing in: Fences, walls and shrubs that trap exhaust air will lower output.
• Roof runoff: Keep the unit out from under an eave without a gutter.
• Other equipment: Keep it away from gas heater exhaust and from A/C condensers blowing toward it.
• Noise: Heat pumps sound like a central A/C unit, so keep them away from bedroom windows.
• Sprinklers: Aim them away from the unit.
• Plumbing distance: Keep it close to the equipment pad to limit pipe runs and heat loss.

The pad and condensation

Set the unit on a level, raised pad so it stays out of standing water and debris. Heat pumps produce a lot of condensation and can put out several gallons an hour in humid weather. That's normal. Make sure it drains away from the equipment and the house.

Water under the unit? Test it. Dip a chlorine test strip in the water. Condensation won't show any chlorine. If the strip reads chlorine, you have a plumbing leak.

Electrical

• Most residential pool heat pumps run on 208/230V single-phase power on a dedicated circuit.
• Size the breaker and wire from the nameplate's minimum circuit ampacity and maximum breaker size. Residential units commonly need a 30–60 amp breaker, depending on size. Long runs may need larger wire to limit voltage drop.
• Install a disconnect within sight of the unit if your code requires it.
• Connect the #8 solid copper bonding wire to the unit's bonding lug.
• Follow local code for GFCI protection.

Plumbing and flow

1. Position: After the filter and before any chlorinator or salt cell. If you also have a gas heater, the two are typically plumbed in series, and the manual shows the order.
2. Unions: Use them on the inlet and outlet for easy service and winterizing.
3. Flow range: Most residential units want flow within a set range, often somewhere around 30–70 GPM, so check your spec. If your pump pushes more, add a bypass valve so the heat pump sees the correct flow.
4. Flow or pressure switch: The heat pump won't run unless it senses flow. With a variable-speed pump, set a speed high enough to close the switch whenever you're heating.
5. Height above the water: If the unit sits well above or below the water level, the water pressure switch may need adjusting per the manual.

Start-up and getting the most heat

1. Start the pump and confirm steady flow.
2. Turn on the heat pump and set the target temperature. Most units wait a few minutes before the compressor starts. That delay is a built-in protection.
3. Cold air from the fan and dripping condensation mean it's working.
4. A heat pump only heats while water flows. Run the pump long enough each day, and schedule heating during the warmest hours, usually late morning through afternoon, when efficiency is highest.
5. Use a solar cover, especially overnight.

Maintenance

• Keep leaves and grass clippings off the coil. Rinse it gently with a hose, never a pressure washer, which bends the fins.
• Keep water chemistry balanced. Titanium heat exchangers resist corrosion but can still scale up in hard Texas water.
• During a hard freeze, keep water moving with freeze protection, or drain the unit as the manual describes.

Heat pump vs gas heater

Pool heat pump FAQs

How long does a heat pump take to heat a pool?

The first heat-up can take a day or more depending on size, air temperature and how much you're raising it. After that, it holds temperature with much less run time.

Can a heat pump heat my spa?

Yes, but slowly. For on-demand spa heat, most owners pair a heat pump with a gas heater.

Will a heat pump work in winter in Texas?

Along the Gulf Coast and in South Texas, often yes. In North and West Texas, output drops on cold days, so a defrost-capable model or gas backup is the usual fix.

Why is water pooling under my heat pump?

It's almost always condensation. Test it with a chlorine strip. No chlorine means it's normal.