Brochure

Parker Hannifin Corporation
Climate & Industrial Controls Group
Cleveland, OH
Catalog CIC-2003-1/US
Refrigeration Solenoid Valves
256
Typical Applications
Typical Applications
Evaporator Temperature Control
A solenoid valve installed in the liquid line as close
to the evaporator as possible, in conjunction with
a narrow differential thermostat, is an excellent
temperature control. By mounting the thermostat
bulb in the supply or discharge air across the
evaporator, the temperature swing is limited only
by the differential of the thermostat.
This type of temperature control can be used on a
single or multiple evaporator system and is particu-
larly useful on multiplexed systems with evaporators
at different temperatures.
Defrost Pump Down
In situations where the condensing unit is installed in a
low ambient, such as on a rooftop in northern climates,
and the evaporator is operating at a temperature above
the ambient, a pump down solenoid valve should be used.
This allows the pressure control to be set at a cut out of 1
to 2 psi and the cut in to be set at a pressure below the
pressure corresponding to the ambient temperature. This
will insure that the condensing unit will start after cooling
down during the defrost.
When a system has a defrost pump down solenoid valve,
a thermostat should be used in series with the time clock
defrost to control the temperature of the space or fixture.
An alternative to the thermostat would be an evaporator
pressure regulator.
Note: System diagrams are for illustrative purposes and
are intended to show application of solenoid valves only.
Heat Reclaim Systems
There are basically 2 types of heat reclaim systems: The
series system and the parallel system.
In the series system, during normal operation, the dis-
charge gas is condensed completely in the condenser.
During the heating mode, the normally opened solenoid
valve closes off the condenser and the normally closed
solenoid opens to allow the discharge gas to flow into the
heat reclaim coil. Complete condensation can occur in the
heat reclaim coil if so designed, but manufacturers often
prefer to take advantage of all the sensible heat available
but only part of the latent heat, depending on the con-
denser for complete condensation.
Thermostatic Control of Evaporator Temperature
Thermostatic Control of Two Separate Evaporators
Pump Down Defrost with Low Ambient Conditions