This extended care hospital facility uses a significant amount of hot water and was due for a new hot water system to replace the failing one. The solar hot water preheat system will provide nearly 50% of the load annually to the building. A drainback, preheat configuration with double wall heat exchanger was selected due to site circumstances, performance and reliability. This solar thermal system is a drainback system. In the event of system failure, tank maximum temperature or freezing conditions, the circulating pump is shut down and the fluid drains back to the storage tank inside. This allows the working fluid to be simply distilled water reducing cost, pumping energy, maintenance and risk.
Control for this system is done via a standalone, variable speed differential temperature controller. Monitoring, trending and alarming is done via the building automation system. This was to reduce overall cost and improve functionality and reliability.