Figure 1 : Building B HHW Load Profile
Option 1 is a fully electric option with an air-source heat pump operating in heating-only mode to provide 100 % of the building ’ s HHW needs . Although this machine has cooling capabilities , it will be run only in heating mode . This option will consist of two banks of six modules operating in a twopipe configuration in heating-only mode and will not be tied into the campus chilled water system to reject the cooling water . This system is relatively simple : it is stand-alone . The HHW supply temperature was set to 135 ° F ( 57 ° C ) to ensure the existing building coils can meet the loads at the reduced temperature .
In this case , the COP at peak heating operation is approximately 2.12 kW / kW ( 7.5 kW / ton ). The COP will increase if the system can operate at a lower HHW supply temperature ; however , the one-row coils within the building require a HHW supply temperature of 135 ° F ( 57 ° C ) and further reset is not possible without modifying the coils if the site experiences ambient temperatures below 40 ° F ( 4.4 ° C ). In this case , supplemental heating would be required due to limits related to the ambient lift capabilities of this machine .
Option 2 is a fully electric option with a water-cooled heat pump operating in heating-only mode to provide 100 % of the
+ building ’ s HHW needs . This option will consist of a bank of six modules operating in a four-pipe configuration in heatingonly mode that will tie into the campus chilled water system to reject cooling water . The HHW temperature was set to 135 ° F ( 57 ° C ) to ensure existing building coils can meet loads at the lowest possible supply temp . The equipment COP is approximately 5.0 . This option requires pumps on the chilled water side to ensure chiller modules maintain the required differential pressure drop across the heat exchanger .
Option 3 is a hybrid option , which will include a watercooled heat recovery chiller ( HRC ) operating in heatingonly mode to provide 80 % of the building ’ s HHW needs ( roughly 25 % of peak capacity ). This option will consist of a bank of modules operating in a four-pipe configuration in heating-only mode that will tie into the campus chilled water system to reject cooling water . For peak loading , supplemental gas-fired boilers will be provided . The HHW supply temperature was set to at 110 ° F ( 43 ° C ) when the HRC is operating at lowload conditions ( and higher ambient temperatures ) and 135 ° F ( 57 ° C ) when the gasfired boilers are operating at peak heating needs . In this case , the HRC equipment COP is approximately 7.0 .
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