Like regular water heaters, most solar storage tanks of 120 gallon capacity or less
are insulated with fiberglass or urethane foam insulation between the tank wall and
For interior use, the insulation on these smaller tanks should be at least R-12, with
R-20 a better choice.
In some cases additional insulation blankets are installed on the outside of the tank
jacket. If the blanket is maintained, and does not limit access to tank components,
this is acceptable. (Figure 2-46)
For larger tanks, above 120 gallons, even more insulation is appropriate. R-30 is
recommended for tanks whose temperatures are 140F or lower the majority of
time. Tanks which routinely reach over 140F are normally insulated to R-40.
"Blown-on" foam insulation is typically used.
2.7.9 Controls and Sensors, The collection system control operates by
comparing the temperatures of the collectors and storage. When the collectors are
warmer than the storage, collection pumps are turned on. If the collector
temperature falls below the storage temperature, the pumps turn off.
2.7 COMPONENT OPERATION