How solar pool heating works
Your pool pump pushes water through the filter and, when conditions are right, an automatic valve diverts it up to the collectors on the roof instead of straight back to the pool. The water picks up heat as it travels through the collector tubes and returns a few degrees warmer. Repeat for a few hours and the whole pool moves.
A controller decides when that happens. It compares a sensor at the roof with a sensor at the pool, and when the roof is enough warmer than the water, it opens the valve. When it is not, it closes it, which is why the system correctly does nothing on a cool cloudy morning.
What to expect through the Florida year
Solar pool heating in Florida is a year round system, not a seasonal one. What changes is how much it can give you.
Spring and autumn are where it does its best work: strong sun, cooler water, and long useful days. Deep summer often needs no help at all. In the shortest, coolest weeks of the year the sun is lower and the days are shorter, so the gain is smaller, and a pool that is also losing heat overnight can end up close to where it started.
A pool cover changes this arithmetic more than any other single factor, because most of the loss happens off the surface overnight.
The controller and the automatic valve
Two components cause most of the confusion when a system stops performing.
- The automatic valve directs water either to the roof or back to the pool. If it sticks, water either never reaches the collectors or is sent up when there is nothing to gain. You can often hear it move and see the actuator turn.
- The controller relies on its sensors. A failed roof sensor or pool sensor makes the controller act on wrong information, and the usual symptom is a system that never turns on, or one that runs at odd times.
- Most controllers have a high limit setting that stops heating once the pool reaches your chosen temperature. A pool that "stopped working" occasionally turns out to have reached its set point.
Leaks and how to spot one
Collectors, headers, couplings and roof penetrations are all plumbing, and plumbing on a roof in the Florida sun has a working life.
- Water dripping from the eaves or wet patches on the driveway only while the system is running.
- A pool level that drops noticeably faster on days the solar runs than on days it does not. This is the clearest signal there is.
- Visible spray or streaking on the roof when the valve is open.
- Air in the system, or the pump losing prime, after the system shuts down.
Pump and filtration
Solar pool heating has no pump of its own. It borrows yours, and it needs enough flow to lift water to the roof and push it through the collectors.
A dirty filter, a clogged basket, or a variable speed pump programmed too low will all stop the roof from getting water. This is one of the most common causes of a system that used to work and now does not, and it has nothing to do with the solar equipment at all.
Freeze conditions
Florida gets cold snaps. Most controllers include freeze protection that circulates water to protect the collectors and pipework when the temperature approaches freezing. If that protection is disabled, or the controller has failed, exposed plumbing can split.
If your controller is not working going into a cold night, that is a reason to call rather than wait.
Ongoing maintenance and when to call a professional
- Flow and pressure through the system.
- Automatic valve and actuator operation.
- Controller function and both sensors.
- Collector condition, headers, tubes and couplings.
- Roof mounting, straps and penetrations.
- Isolation and check valves.