Trane SYS-APM001-EN manual DP2/DP1 = Flow2/Flow11.85

System Design Options

1.90power, respectively. The examples here use the more conservative 1.85 power:

DP2/DP1 = (Flow2)/(Flow1)1.85

Given different flow rates and entering water temperatures, a different cooling tower can be selected for the low-flow condition (Table 6):

Table 5. Low-flow conditions for chilled-water pump

	Base Case	Low Flow*
Flow rate, gpm [L/s]	1,080 [68.1]	675 [42.6]
System pressure drop, ft water [kPa]	80.0 [239]	33.5 [100]
Evaporator-bundle pressure drop, ft water [kPa]	29.7 [88.8]	12.6 [37.7]
Pump power output, hp [kW]	39.9 [29.8]	10.5 [7.80]
Pump electrical power input, kW	32.0	8.4
Table 6. Low-flow conditions for cooling tower
	Base Case	Low Flow*
Flow rate, gpm [L/s]	1,350 [85.2]	900 [56.8]
Static head, ft water [kPa]	19.1 [57.1]	12.6 [37.7]
Tower fan power output, hp [kW]	30.0 [22.4]	20.0 [14.9]
Tower fan electrical power input, kW	24.1	16.0
Table 7. Low-flow conditions for condenser-water pump
	Base Case	Low Flow*
Flow rate, gpm [L/s]	1,350 [85.2]	900 [56.8]
System pressure drop, ft water [kPa]	30 [89.7]	14.2 [42.5]
Condenser-bundle pressure drop, ft water [kPa]	19.9 [59.5]	9.6 [28.7]
Tower static lift, ft water [kPa]	19.1 [57.1]	12.6 [37.7]
Pump power output, hp [kW]	31.4 [23.4]	11.0 [8.2]
Pump electrical input, kW	25.2	8.8

*Low-flow conditions represented in Table 5 through Table 8 are 1.5 gpm/ton [0.027 L/s/kW] chilled water and 2.0 gpm/ton [ 0.036 L/s/kW] condenser water.

SYS-APM001-EN Chiller System Design and Control 31