Rules of Thumb for Solar Systems
The rules of thumb in this appendix are not intended to replace proper design
procedures. They are included to allow you to determine if an existing system is
operating within generally accepted ranges.
If the manufacturer's design recommendations are available, use them, instead of
these rules of thumb.
All flow rates for collectors are in gallons per minute per gross (overall) square foot
of collector (GPM/sq ft). N.A. is used when that type of fluid is not used with that
If a system appears to be outside of the recommended ranges, and
corrective actions on the system do not bring them back into the
range, get design assistance from personnel on-base or in your
Engineering Field Division (E.F.D.).