Mode specifies the configuration and target temperature for the water-source heat recovery chiller. The available modes include:
A.Pre-cool & pre-heat
The primary function of the Pre-cool & Pre-heat mode is to maximize equipment operation to pre-cool chilled water (evaporator side) and pre-heat hot water (conendser side) as much as feasibly possible at any given time. The HRC will operate at maximum output so long as simultaneous cooling and heating loads are both in excess of the HRC equipment capacity. Upon selecting this mode, the connection to the recipient HWL will be in series before the adjacent equipment specified on the HWLHeating equipment set while the configuration to the associated CHLW will be in series before the other equipment cooling equipment set.
HRCwill operate at part-load only when either CHWL or HWL operational load is less than this total capacity. The operating capacity must be constained to avoid either over-cooling the CHWL or over-heating the HWL by the lesser load relative to the available capacity.
When theheat acquisition-rejection coil is added to the HRL under this mode, the HRCwill continue to operate more like a more typical air-to-water heat pump to serve HWL loads in excess of the heat available on the CHWL.
B.Heating-driven
The primary function of the Heating-driven mode is to meet the heating loads with the recovered heat from the HRC to reach the HWL target supply water temperature. Upon selecting the Heating-driven mode the connection to the recipient HWL will be in parallel with the adjacent equipment specified on the HWLHeating equipment set while the configuration to the associated CHLW will be in series before the other equipment cooling equipment set and condenser side of the HRC will reference the HWL setpoints.
Operational heating capacity at any given time is constrained by load on the cooling side to prevent subcooling of water temperature to achieve the HWL target supply water temperature. This translates to adequate supply of suitably warm return return chilled water. Providing aheat acquisition-rejection coiland/or ability to use existing chilled-water storage tank will extend the heating operation by increasing available heat in the source at any given time. If heating demand load is less than the maximum available from the HRC at any given time, this will constain the heat rejection and coincidentally the operating cooling capacity of the HRC.
The controls logic for the Heating-driven mode modulates hot water flow to maintain the HWL target supply water temperature. This will include any temperature reset established for the HWL. If the HRC cannot achieve supply water temperature at minimum permitted condenser water flow on the HWL then the HRC will disable as there is insufficient heat available on the CHWL (without sub-cooling) and insufficient capacity to achieve HWL supply water temperature at minimum permitted flow.
Decreasing the HWL supply water temperature target as much as feasible will maximize the benefits of the HRC COP and operating hours.
