Ask This Old House showed the installation of a system that captures the heat from the AC unit to heat a swimming pool. The AC refrigerant line runs through a coil inside a canister. The pool water runs through the canister and the heat is extracted.
OK, that's all well and good. Efficient, free heat heat for a pool which is shaded by trees and gets very little sun.
Let's think about this. When it's hot out, the AC is running and pool gets heated. When it's cool out, the AC is not running, so the pool does not get heated.
Sure, there's some advantage to heating the pool on a hot day, even into the hot night. However, on a cool day or cool evening, when the owner would really want the pool heated, he's right back where he was before the system was installed. Early and late in the season, when it's not hot enough for the AC to be running for any length of time, there is no heat available for the pool - right at the times of the season when you would want it.
Considering that it takes a certified AC tech to capture the refrigerant, adapt the AC piping and recharge the system, is it really worth installing one of these systems? I don't have a pool, so I don't know how cold the water in a shaded pool would be on a day hot enough for the AC to be running.
After a few days of cool weather, how long would would the AC have to be running for it to heat the pool to something that would be comfortable? Yes, I know it depends on the size of the pool and how cool it was. The one in the show was a decent sized in ground pool. Is it a matter of a few hours or would it take all day or longer? I know there's a number of variables involved...just looking for some idea.
It just seems kind of bass-akwards to only have heat available on hot days.