Brochure

Parker Hannifin Corporation
Climate & Industrial Controls Group
Cleveland, OH
Flo-Con Pressure Regulators and Valves
340
Catalog CIC-2003-1/US
The Parker Refrigerating Specialties Division has built
a reputation as a principal supplier of reliable, high side
control valves to the supermarket industry. One of the
more critical applications on a commercial refrigeration
system where hot gas is utilized for defrosting pur-
poses is the use of a regulator in the discharge line.
Refrigerating Specialties types A81BL or A82BL have
become a standard for many supermarket rack manu-
facturers specifically for this application.
The “BL” version of an A8 regulator in a discharge
application serves two functions. The valve is either in
a wide open (or bypassed) position with it’s solenoid
energized to facilitate a minimum pressure drop
through the valve when no refrigeration circuits are
calling for defrost. In this mode, the valve essentially
is acting as a low pressure drop solenoid in an opened
position. When a refrigeration circuit begins a defrost
sequence however, the solenoid on the discharge
A8_BL regulator is de-energized (via the defrost
program), thereby converting the valve into a differen-
tial pressure regulator.
A differential regulator communicates outlet pressure
into the valve’s bonnet in order to compensate range
spring pressure with downstream pressure. The set
point of the valve thus becomes the sum of spring
pressure plus outlet pressure. Whatever the range
spring pressure is set for effectively becomes the pres-
sure difference the valve will maintain from its inlet to
outlet. If, for example, the regulator was set to maintain
a 25 psi set point, the valve will regulate and maintain
an upstream pressure 25 psi higher than it’s down-
stream pressure, regardless of fluctuations in down-
stream pressure. In this application, the regulator
Discharge Regulators for Supermarket Applications
ensures that the hot gas pressure supplied to a circuit
for defrost purposes will be high enough to overcome
the pressure drop through the supply line, the losses
through valves and fittings, and through the evaporator
coil. The defrost condensate exits the evaporator and is
then introduced, at an elevated pressure, back into the
liquid line.
Because each system may vary due to any number of
design considerations, the A81BL and A82BL regula-
tors are field adjustable. The regulator can therefore be
adjusted to determine the most efficient set point while
ensuring that each evaporator defrosts in a timely and
thorough manner.
For larger systems that exceed the capacity of the A8
regulator line, Refrigerating Specialties offers a higher
capacity flanged valve for discharge applications, the
A4AB or A4ABL.
For sizing, please see “Discharge Capacities” on pages
312 – 319.
Figure 5 - Discharge regulator for
supermarket applications. (See page 346 for symbols legend.)
Technical Information Discharge Regulators
Label Valve Function Application Design
Selection
Page
A Inlet Pressure Regulator Discharge Pressure A8 312-319
B Solenoid Valve Liquid Feed SC 343
Valve Legend