5.1.4 System parameter worksheet. Worksheet 3 is provided to help keep
track of the various system parameters that must be calculated or obtained
from Appendix A. Note that the worksheet allows for the presence of two
passive solar heating systems on a building and provides formulas for
calculating the properties of the resulting mixed system.
The first step in filling out the worksheet is to calculate the thermal
storage characteristics of the building. For direct gain or radiant panel
systems, the EHC must be determined. If the thermal storage mass properties
and configuration correspond closely to one of the reference designs in
Appendix A, simply enter the specified EHC/Ac in the indicated blank on
the worksheet; the diurnal heat capacity per ft2 of aperture, DHC/Ac, is
then found from the same reference design. Otherwise, it will be necessary
to calculate the EHC and the DHC as described in 5.1.2 and to evaluate
DHC/Ac as outlined below.
Among the remaining reference designs, only TAPS and concrete block
Trombe walls have specified levels of interior mass. For the concrete block
Trombe walls, the interior mass provides secondary thermal storage to the
wall itself and only one representative level is treated (high density
concrete with a thickness of 4 inches and a surface area three times greater
than the block wall area). The TAP reference designs have the same interior
mass options available for direct gain systems. The DHCs for concrete block
walls and TAPs are specified in Appendix A for the reference designs.
After entering values of the EHC/Ac and DHC/Ac on Worksheet 3,
proceed to the first (or only) set of system parameters. Enter the system
type and number (from Appendix A). If interpolation on the EHC has been
employed, enter the numbers of both systems involved. Then enter the first
set of system parameters on the worksheet. Finally, enter the size of the
first solar collection aperture (using projected area for sunspaces).
If two types of passive solar systems are present on the building,
proceed to the next part of the worksheet and enter a second set of
parameters. Next, calculate the area fractions of the two systems and use
the formulas provided on the worksheet to calculate the parameters for the
5.1.5 Effective thermostat setpoint. Auxiliary heat consumption can
often be reduced significantly by setting back the thermostat at night. In
necessary to determine the effective thermostat setpoint, Te, for use in
the base temperature calculation.
The first step is to calculate the average thermostat setting from the
Tave = T1(hr1/P) + T2(hr2/P)
where T1 and hr1 are the temperature and duration (in hours) of the
first setting, T2 and hr2 are the temperature and duration of the second
setting, and P is the period of the diurnal cycle (24 hours).