Solar Thermal Information

11
FORCED-AIR DISTRIBUTION SYSTEMS:
Although most solar combisystems use hydronics
technology, it is possible to use a forced-air system to
deliver both the solar-derived heat and any necessary
auxiliary heat to the building. This is usually done using a
hot water coil mounted in the plenum of the air handling
device (furnace, heat pump indoor unit, etc.), as shown
in figure 3-10.
The coil is mounted on the discharge plenum to avoid
heating the components inside the air handler. Although
this may not be an issue with devices such as furnaces,
it could void warranties on other types of air handlers
containing refrigeration components.
The check valve installed in the pipe supplying the
plenum coil prevents reverse heat migration from the
furnace to the solar storage tank when the latter is too
cool for use.
An air temperature sensor is located in the discharge
plenum, downstream of the coil. This is used in
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 20 40 60 80 100 120
Correction factor (CF)
∆T (ave water temp - room air temp) (ºF)
CF = 0.001882 ∆ T
( )
1.33
Reference condition:
Ave water temperature in panel = 180ºF
Room air temperature = 68ºF
reference condition
∆T=112 ºF
thermostatic
radiator valves
(TRV) on each
radiator
TRV
TRV
TRV
TRV
TRV
TRV
manifold station
small diameter 
(3/8", 1/2", 5/8") 
PEX or PEX-AL-PEX
panel radiator
figure 3-8
figure 3-9