Cold Room Condensing Unit Air Volume: 2500 M3/hr

Bohns most energy efficient low ambient head pressure control. This system provides year round control
of refrigerant head pressure without the use of special refrigerant expansion valves.
Resource II combines the benefits of refrigerant subcooling and reduced discharged pressure during mild
ambient conditions. As the ambient temperature falls
the receiver pressure is allowed to fall to a minimum
of 75 F. saturated condensing pressure. The reduced
discharge pressure at the compressor increases the
compressor capacity and lowers the input watts from
the compressor motor. Resource II also uses the reduced ambient temperature to subcool the liquid refrigerant in the condenser. This subcooled liquid also
increases system capacity. As a general rule, every
one degree of subcooling results in a 1/2% increase
in system capacity. Together these result in greater
efficiency, greater capacity, and reduced run time.
Benefits
Automatic year round control of refrigerant
head pressure without the use of special
expansion valves.
Energy savings in mild ambient conditions due
to reduced compressor discharge pressure and
refrigerant subcooling.
Provides easy restart during low ambient
conditions.
Operation
As the ambient temperature falls, the system condensing pressure is also reduced. This pressure is maintained by a regulator (ORl-6-65/225) at the condenser
drain. At approximately 75F. saturated condensing
pressure the regulator restricts the flow of liquid refrigerant from the condenser causing the condenser
to flood. This condenser flooding allows the liquid
refrigerant in the condenser to become subcooled by
the ambient air flowing through the condenser. As the
regulator continues to flood the condenser a pressure
differential will be established between the receiver
and the compressor discharge. At a predescribed
differential, a second valve (ORD-4) will open and allow
discharge gas from the compressor to bypass the condenser and flow into the top of the receiver. This gas is
used to pressurize the receiver.
Both the inlet and outlet tubes of the receiver have dip
tubes which are immersed in liquid refrigerant. The liquid in the receiver acts as an insulator from the vapor
area of the receiver. This unique design minimizes the
contact of the hot gas used to pressurize the receiver
through the ORD-4 valve. This allows bypass vapor to
pressurize the receiver while reheat of the subcooled
liquid is minimized.
Subcooled liquid is further enhanced by the routing of
liquid from the receiver liquid line outlet to the condenser before leaving the condensing unit.