System information

30
Geothermal Applications
ClimateMaster: Smart. Responsible. Comfortable.
Loop Sizing
Like equipment sizing, properly designed residential geothermal
loops require the use of GeoDesigner software. Loop type and
confi guration are addressed earlier in this manual. Therefore, the
loop type will depend upon the available space and economic
considerations (excavation costs, etc.). Loop sizing involves the
calculation of the amount of loop piping required. A load calculation is
required in order to use the GeoDesigner software, since equipment
and loop are determined based upon heat loss/heat gain.
ClimateMaster heat pumps are designed for EWTs of 20°F [-7°C]
to 120°F [49°C]. However, economical minimum and maximum
loop temperatures should not be outside the range of 25°F
[-4°C] and 105°F [41°C]. A good starting point for minimum
EWT is 30 to 40°F [17 to 22°C] above the winter outdoor design
temperature. For maximum EWT, a good starting point is 90 to
100°F [32 to 38°C]. For example, for a location with a 0°F [-18°C]
design temperature, a good starting minimum EWT would be 30°F
[-1°C]. Generally speaking, climates where heating is the dominant
factor, maximum EWT should be closer to 100°F [38°C], since
cooling costs will be less of a factor than heating costs. In Southern
climates, maximum EWT should be lower (closer to 90°F [32°C]),
since lower cooling EWT will provide higher effi ciencies and thus
keep cooling cost low.
Once starting minimum/maximum EWTs have been determined,
enter the values into GeoDesigner (see illustration below). Adjusting
the loop EWTs will change the amount of loop required. As long
as the minimum and maximum EWT remains in the 25°F [-4°C] to
105°F [41°C] range, loop sizing is primarily an economic decision.
More loop yields milder operating temperatures, which lowers
operating costs, but increases installed costs. In some cases, it
may even be more cost effective to increase the loop length to
allow the use of the next size smaller heat pump, since milder loop
temperatures increase heat pump capacity.
Figure 20: GeoDesigner Loop Sizing
ASHRAE Summer and Winter Comfort Zones (S.I. Units)
Acceptable ranges of operative temperature and humidity for people in typical
summer and winter clothing during primarily sedentary activity.
Loop Sizing