Retrofit

Retrofitting Strategy	Enlargement of fresh air inlet and ductwork for free cooling application with low ambient temperature and relative humidity
	During autumn and winter seasons, the outside air is often cooler and dryer than the air inside the building. If the outside air enthalpy (temperature and humidity) is lower than the indoor environment, free cooling mode will be activated to bring in full fresh air from outside to cool the building without using the central chiller plant.
	Consideration
	Needs to have adequate space for the extra ducting arrangement. Requires additional air louvre area provisions. May require additional pusher fan to provide fresh air.
	Estimated Saving
	Waterside (Free Cooling): (1/COP_CH_PRE QBLDG_FC – 1/COP_CH_FCQBLDG_FC)* OPHR,FC Where COP_CH_FC is the COP of chiller plant during the free-cooling period (COP_CH_FC – COP_CH_PRE)/ COP_CH_PRE = 1.25% per 1°C increase of TCHWS COP_CH_FC = [1.25%(TCHWS_FC – TCHWS_PRE) + 1]COP_CH COP_CH = ~~0.605COP_CH_SM +~~ 0.395COP_CH_WN COP_CH_WN = (COPa_WN + COPb_WN)/2 QBLDG_WN = 0.395[0.596(0.184NCH_SMQCH_SM + 0.816NCH_WNQCH_WN)] QBLDG_FC = x%QBLDG_WN OPHR,FC = y%OPHR,yr Airside (WN modeàDAHS mode): kW_AHU_PRE * (LF_WN,PRE – LF_DAHS,POST)* NAHU * OPHR,FC For CSD: LF_DAHS = LF_WN = 1, For VSD: LF_DAHS = 0.795, LF_WN = 0.562; For EC or DC-motor: LF_DAHS = 0.71, LF_WN = 0.38 Please click HERE to view the list of terminology.