Trane SYS-APM001-EN manual Retrofit opportunities, System Design Options, range

System Design Options

Table 11. Retrofit capacity changes

				Larger
		Present		chiller,
				same tower
Capacity, tons		450	[1,580]	675	[2,370]
[kW refrigeration]
Cooling tower	Flow rate, gpm [L/s]	1350 [85.2]		1,350 [85.2]
	Entering temperature, °F [°C]	94.3 [34.6]		103 [39.4]
	Leaving temperature, °F [°C]	85	[29.4]	88	[31.1]
Ambient wet-bulb		78	[25.6]	78	[25.6]
temperature, °F [°C]

It quickly becomes evident that the same cooling tower and flow rate are adequate to reject more heat—in this case, approximately 50 percent more heat.

Figure 22. Cooling tower re-selection with different chiller capacities

Cooling Tower Water Temperature (°F)

90

85

80

75

70

Reselected tower for 50% more heat rejection with 15°F [8.3°C]

range Y

Original design point for tower with 10°F [5.6°C] range

Design Point (original)

Y Design Point (new)

65

55 60 65 70 75 80

Wet-Bulb Temperature (°F)

Retrofit opportunities

The low-flow concepts for chilled- and condenser-water just described in pages 33 through 37 present tremendous retrofit opportunities. Building owners may need to increase the capacity of an existing system, for example, in response to a building addition. In many of these buildings, the condenser water system (piping, pump, and tower) is in good condition, but is considered to be too small. Or, the system has expanded but the chilled water pipes and/or coils cannot be changed. By changing from traditional design conditions, the existing infrastructure can often be used while providing additional capacity.

SYS-APM001-EN Chiller System Design and Control 37