Heat pumps are reverse-cycle air conditioners. They take the heat from the air and put it in the pool. So, the warmer the day, the more efficient the heater. And the opposite is true too. There are a few days of the year here in South Florida that heat pumps don't work. That's when the temperature is in the 50s or below. There's just not enough warmth in the air to put in the pool. The heat pump will operate, it just won't heat the pool. You have to be careful not to ice up the heat pump. It's the same as a house air conditioner set at 50 degrees. The air conditioner will do it's best to try to cool, but ice starts to form on the cold pipes. Especially if there's any humidity in the air.
Heat pumps have energy efficiency ratings and sizes. It's important to buy one that's big enough for the pool.
Heat pumps may have a bypass valve plumbed into them. This is a short section of pipe that goes between the intake and discharge pipe. It allows you to send water back into the pool without going through the heater. Thus, the friction-loss that the heater creates is bypassed. The bypass should be open when you're not using the heater and closed when you are.
Heat pumps generate a large amount of condensate. Especially if it's humid. The whole bottom pan of the heat pump is a condensate tray. There is an outlet on the tray to allow the water to drain off. Here in South Florida, a heat pump can generate up to a gallon an hour of condensate. I always tell customers this so that they won't think there's a leak in the pool.
Heat pumps have flow and pressure sensors. There has to be an adequate flow of water to the heat pump in order for it to turn on. A very dirty pool filter is the most common reason a heat pump won't run.
Some heat pumps have a cool-down feature. This keeps the pump running for a few minutes after the system is shut off to rinse the hot water out of the heater.
Cold air should be felt coming out of the top of the heat pump when it's running. If the air isn't cold, it usually means that the heat pump needs Freon.
Be careful attaching hold-down straps or brackets to a heat pump. The Freon coils are located low on the inside of the unit. A hole in the Freon tubing can be repaired by an a/c guy.
Heat pumps have two main components; the compressor and the fan. Both of them are big electric motors that use capacitors to start. A “boost capacitor” can be used to boost a weak capacitor.
Some heat pumps have two thermostats. One for the pool and one for the spa. The heat pump doesn't know the difference between the two. All it knows is “call for heat”. If you have a pool/spa combination, you should have a heat pump with two thermostats. If a controller is used on the system, the thermostats in the controller override the ones in the heat pump. I recommend keeping the pool thermostat in either the lowest setting or off. That's so that you don't accidentally heat the pool.
