Solar Thermal Information

38
water from solar storage tank. Inactive components in the
lower schematic are shown in gray.
The upper schematic in 5-15 shows the system supplying
space heating from the solar storage tank. The lower
schematic shows the system supplying space heating
from using the boiler as the heat source and the storage
tank as a buffer. Inactive components are shown in gray.
DRAINBACK COMBISYSTEM #4:
Some solar combisystems may include auxiliary heat
sources that also require a storage tank. One example
is a system using a wood-fired boiler. In these cases, it’s
often possible to combine the storage requirements into
a single tank, as shown in figure 5-16.
This system is built around an unpressurized storage tank.
Such tanks typically have an insulated structural shell
supporting a flexible waterproof liner. They are vented to
the atmosphere and thus not capable of operating under
pressure. The air space above the water is sufficient to
accommodate thermal expansion of the water. All piping
connections are usually made above the water level to
minimize any potential leakage with age. An example of
a large (550-gallon) unpressurized storage tank (partially
assembled) is shown in figure 5-17.
unpressurized buffer tank w/ suspended copper coils
wood-fired boiler
vent
sight
glass
solar loop circulators
must be rated for
"open" systems
All solar circuit piping
sloped minimum 
1/4" per ft.
diverter
valve
anti-scald
tempering
valve
temperature
controller
make-up water
make-up water
outdoor
temperature
sensor
(P2)
pressure-
regulated
circulator
space-heating circuits
(highly zoned)
manifold valve actuator
thermostat
end switch leads
3-way
motorized
mixing
valve
end switch leads from actuators
anti-condensation mixing valve
hot
cold
lift head
(P1)
(P3)
solar collector array
sensor in closed copper tube
closely
spaced
tees
relay
copper coil heat exchangers
PRV
hose bib valve
(for draining collector loop
& adding water to tank)
time delay relay
(modulating)
water heater
Image courtesy of American Solartechnics
figure 5-16
figure 5-17