These systems have the following advantages:
- They are simple, cheap and easy to install compared to most active systems.
- They offer more collector placement options than an ICS setup.
- They provide cold weather protection, provided freezes are mild, infrequent and short.
It's also important to consider the disadvantages:
- They require a water softener, installed before the collector array.
- They must use a microprocessor-based controller.
- They cannot use a PV-powered pump.
- Freeze protection is very limited.
- Recirculation reduces system efficiency and increases backup heater operating costs.