Retrofit

Retrofitting Strategy	Conversion to variable speed chilled water pump
	Both primary circuit of de-coupler system and differential by-pass chilled water system uses constant speed pumps. Most of the time, the system operates at part load and required less amount of chilled water flow. Converting the constant speed pump to a variable speed pump with the corresponding control system can reduce the overall system pressure and hence reduce the energy consumption of the chilled water pumps.
	Consideration
	A review on the whole system should be first carried out to determine the plant conversion scenario in order to maximize the benefits of the retrofitting works such as converting the de-coupler system to an all-variable flow when secondary pump has sufficient pump head to drive chilled water through chiller directly and bypassing the primary pumps. Both allowable maximum and minimum flow through chiller should be checked for consider variable flow through chiller. For system with different capacities of chillers, the control of different flow through Installation of power meter, differential pressure sensors together with the flowmeter and VSD devices for monitoring the power and W/L/s of air-conditioning pumps (Figure 2).
	Estimated Saving
	(SkW_CHWP_PRE – SkW_CHWP_POST) OPHR,yr Where S kW_CHWP_PRE = 0.605LF_SM,PRE(0.88NCHWP_SMkW_CHWP_SM + 0.12NCHWP_WN* kW_CHWP_WN) + 0.395* LF_WN,PRE (0.184NCHWP_SMkW_CHWP_SM + 0.816NCHWP_WNkW_CT_WN) SkW_CHWP_POST = 0.605LF_SM,POST(0.88NCHWP_SMkW_CHWP_SM + 0.12NCHWP_WN* kW_CHWP_WN) + 0.395* LF_WN,POST(0.184NCHWP_SMkW_CHWP_SM + 0.816NCHWP_WNkW_CHWP_WN) For CSD: LF_SM = LF_WN = 1, For VSD: LF_SM = 0.795, LF_WN = 0.562; For EC or DC-motor: LF_SM = 0.71, LF_WN = 0.38 OPHR,yr = hr/dayday/wk*52 Please click HERE to view the list of terminology.