Unit Options
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IM 926-3 • ROOFPAK APPLIED SYSTEMS
Ground Fault Protection
The ground fault protection is designed to protect motors
from destructive arcing ground faults. The system consists of
a ground fault relay and a ground fault current sensor. The
ground fault relay employs solid state circuits that will instantly
trip and open a set of relay contacts in the 115-volt control
circuit to shut the unit down whenever a ground fault condition
exists. The ground fault relay is self powered. The ground fault
sensor is a current transformer type of device located on the
load side of the power block through which the power wires of
all phases are run.
Phase Voltage Monitor
The phase voltage monitor (see
) protects against
high voltage, phase imbalance, and phase loss (single
phasing) when any one of three line voltages drops to 74% or
less of setting. This device also protects against phase reversal
when improper phase sequence is applied to equipment, and
low voltage (brownout) when all three line voltages drop to
90% or less of setting. An indicator run light is ON when all
phase voltages are within specified limits. The phase voltage
monitorcontacts wired to the 115-volt control circuit to shut
the unit down whenever the phase voltages are outside the
specified limits.
Hot Gas Bypass
CAUTION
Do not touch gas liner during valve checkout. The hot
gas line can become hot enough in a short time to cause
personal injury.
Hot gas bypass is a system for maintaining evaporator
pressure at or above a minimum value. The purpose for
regulating the hot gas into the distributor is to keep the velocity
of the refrigerant as it passes through the evaporator high
enough for proper oil return to the compressor when cooling
load conditions are light.
The system consists of a combination of solenoid valves and a
pressure regulating valve as shown in
. The solenoid
valves are factory wired to open whenever the controller calls
for the first stage of cooling. The pressure regulating valve
starts to modulate open at 57 psig (393 kPa).
Adjustments are made by turning the adjustment screw on the
pilot valve. Turning the screw clockwise will increase the valve
setting. Turning the screw counterclockwise will decrease the
valve setting. The average psi charge per turn of adjustment is
16 psi.
The regulating valve opening point can be determined by
slowly reducing the system load or reducing the required
discharge air temperature setting while observing the suction
pressure. When the bypass valve starts to open, the refrigerant
line on the evaporator side of the valve will begin to feel warm
to the touch.
Figure 96: Hot Gas Bypass System
Combination modulation
and solenoid valves
Hot gas bypass line,
circuit #2
Hot gas bypass line,
circuit #1
To evaporator
Summary of Contents for RoofPak RPS Series
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