Instead of relying on glycol for freeze protection this system allows all the water in the array to drain back from the array and into a storage vessel in the solar loop when the pump is turned off.
Indirect solar water heater system.
6 5 16 in a direct system the service water is directly circulated between the water tank and the collector while in an indirect system a heat transfer fluid usually antifreeze distilled water.
Active indirect systems in which a heat transfer fluid like propylene glycol is heated up within the solar collectors and then transfers the heat to the water supply with a heat exchanger in a closed loop system.
The optimum installation can be constructed by using different accessories.
Active solar heaters are primarily of three types direct indirect and drain.
Indirect solar system ite.
Conventional storage water heaters usually provide backup and may already be part of the solar system package.
The indirect solar system ite consists of an indirect tank which is connected to a boiler electric gas or oil or water heater.
Indirect solar water drainback systems are also a indirect design that use a heat exchanger to separate the collector loop from the potable water.
Swh systems which do not include a heat exchanger are called direct systems shown in fig.
Solar water heating systems almost always require a backup system for cloudy days and times of increased demand.
6 4 while the swhs which are fitted with heat exchangers are called indirect systems shown in fig.