| 摘要 |
Condensing head pressure in a refrigeration system having its condenser exposed to low outside ambient temperatures is controlled to provide the minimum head pressure required for a given mode of operation. A hierarchy of operating modes, each with its associated pressure is established, including normal refrigeration, evaporator defrost and heat reclaim. The control system prevents system head pressure from going below the minimum required for the operating mode in effect at a given time, with modes requiring higher pressure overriding lower pressure modes when required. In heat reclaim operation, high pressure gas from the compressor is diverted through a heat reclaim coil, and a subcooling sensor or other sensing means controls system head pressure to the minimum pressure that will maintain full condensing in the heat reclaim coil, which is the most economical mode of operation. In a multiple system, head pressures of the various systems are brought up sequentially to the pressure for full condensing in their heat reclaim coils so that if additional heat is needed the next stage is brought in, rather than further increasing the pressure of the previous stages. This has been found to be more economically efficient than providing further increases in head pressure above the optimum point of just fully condensing all vapor entering the reclaim coil to liquid. |
