Brochure

Parker Hannifin Corporation
Climate & Industrial Controls Group
Cleveland, OH
Flo-Con Pressure Regulators and Valves
306
Catalog CIC-2003-1/US
Condenser Pressure Control
For Air Cooled Condensers
Parker Refrigerating Specialties and Flo-Con regulators
provide the wide range of adjustment of condenser
and receiver pressures required for the most efficient
operation of large air-cooled condenser systems. The
regulators are an integral part of the refrigeration
system and provide direct control of condenser and
receiver pressures to achieve satisfactory system
operation with minimum energy consumption.
Condenser pressure control is needed for one or more
of the following reasons:
1. To maintain sufficient receiver pressure to insure
flow of an adequate amount of liquid to the evapora-
tor for proper temperature control and adequate
refrigeration capacity.
2. To permit start up during cold weather conditions by
quickly developing adequate receiver pressure.
3. To provide an ample supply of hot gas for defrosts,
reheat or heat reclamation systems.
4. To prevent flash gas in the liquid lines. With no
pressure control, at very low ambient temperatures
the cold liquid may be at almost saturated conditions
because of the low condensing pressure. The lack of
sub-cooling may cause the liquid to evaporate when
the liquid lines pass through warm areas or where
pressure drops take place (filters, valves, etc.). The
presence of flash vapor would affect the perfor-
mance of expansion valves, eroding seats, causing
irregular flow, and reducing capacity.
Types of systems
Two systems of variable condenser pressure control
are shown on the opposite page. Figure 1 shows a
Liquid Drain Control Method using a regulator in the
liquid line to provide the desired condenser pressure.
This method is ideal for large capacity systems since
a smaller regulator is required for liquid line than for
discharge line.
Figure 2 shows a Discharge Gas Control Method
using a regulator in the discharge line. In both cases a
bypass regulator is used to control the receiver pres-
sure by feeding it with high-pressure gas as necessary.
This method is particularly suitable for systems requir-
ing hot gas defrost, heat reclaim, and for ease of start
up of systems with a cold receiver.
Valve Functions
Valve A in Figure 1 is an Inlet Pressure Regulator in
the liquid drain line from the condenser, and senses
the condenser pressure. The regulator closes as the
condenser pressure drops below the set point, thus
back flooding the condenser and reducing the inside
surface area available for condensing.
Valve B in Figures 1 and 2 is an Outlet Pressure
Regulator in the bypass line from compressor
discharge to the condenser liquid drain line. This valve
senses the receiver pressure and opens when the
pressure drops below the set point, thus maintaining
the receiver pressure.
Valve C in Figures 1 and 2 is an In-line Check valve
in the liquid drain line to prevent higher pressure from
backing up into the condenser during low ambient
conditions when the compressor is idle.
Valve D in Figure 2 is an Inlet Pressure Regulator in the
compressor discharge line. This regulator senses the
discharge pressure and closes as the pressure drops
below the set point, thus maintaining the discharge
pressure at the desired level.
Technical Information Condenser Pressure Control