Florida schools recommend:

• Aim South or at least within 45 degrees of South.
• Piping should be drainable (preferably from the equipment room), avoiding air and liquid traps. The designer should specify slopes & attachment methods.
• Use reverse return piping instead of balancing valves for balancing.
• Pair a relief valve with the collector isolation valve.
• Use automatic (not manual type!) air vents on system high points except for drainback systems.
• Draindown systems (not other types) need a vacuum breaker to let air back in.
• Temperature relief valves should be located at points of maximum temperature.
• Minimize distances between collector and solar storage tank, thence to backup tank, thence to point of usage/load. Heat loss is proportional to distance.
• Insulate the piping and cover the insulation. Foam wraps break down in the sun even when painted so wrap pipes with aluminum tape or a metal jacket.
• The (hot) sensor on the collector should be at the collector exit, preferably inside the collector box.
• The (cold) sensor on the supply piping should be at the tank (bottom) exit pipe.
• Install and label, but do not connect, spare hot and cold sensors: very helpful after failures.
• Select a controller that displays sensor temperatures, has extra input ports, and has a "pump running" indicator (e.g., a light). Provide a fluid flow rate meter. Every heat exchanger needs temperature sensors on input and output (show the log mean temp difference).
• Wire it up carefully; 30% of installations required rewiring by FSEC.
• A vertical axis tank stratifies water by temperature so the coldest gets heated, which is the most efficient way.
• Size the solar tank to provide 65\% of a typical day's hot water load. Provide 1-2 gallons per square foot of collector. Too big or small creates inefficiencies.
• Insulate the tank and piping, including between solar and backup tanks, and even the cold water supply piping. Piping heat losses can be significant. Insulate valves, circuit setters, heat exchangers, and even pumps.
• Label pipes with fluid type and direction. Label valves, etc., that are covered by insulation.
• Re-check the check valve orientation and direction, a common error.
• Hot water circulation loops should be avoided if possible (major heat losses), or else controlled by timers (with backup batteries!) to eliminate unneeded hours of operation but to operate when needed.
• Provide a bypass valve to feed cold water directly to the backup heating system when the solar system is temporarily shut down. Label it clearly so it will not be left open after the shutdown is over.
• Don't undersize the heat exchanger in a closed loop system, thereby reducing efficiency. Oversize works better than undersize in this case.
• Freeze protection.
  • 1/3 of visited Florida school systems had freeze damage.
  • Recirculation freeze protection is little protection.
  • Use draindown or drainback design or an antifreeze system.
  • On draindown systems, put the automatic drain valve in a non-freezing environment.
  • Draindown and drainback systems require an operator to periodically check that valves and tanks are still working, and that collectors are refilling after a freeze is over.
• Operations and Maintenance requires a operator trained to tell when the system is and is not working, and an O\&M Manual for that specific system describing exactly how that system works and with instructions for operation and maintenance. Don't accept the system without such a manual.
• Periodic (semi-annual or at least annual) inspection should check the collector, piping, insulation, valves, sensors/instrumentation, and the controller, and should measure overall system efficiency.