62
IOM 1206-1
Component Operation
Component Operation
Hot Gas Bypass (Optional)
This option allows the system to operate at lower loads without
excessive on/off compressor cycling. The hot gas bypass
option is required to be on both refrigerant circuits because of
the lead / lag feature of the controller.
This option allows passage of discharge gas into the
evaporator inlet (between the TX valve and the evaporator)
which generates a false load to supplement the actual chilled
water or air handler load.
Note:
The hot gas bypass valve will not generate a 100% false
load.
The pressure regulating valve is factory set to begin opening at
102 psig with R-410a and can be changed by changing the
pressure setting. The adjustment range is 75 to 150 psig. To
raise the pressure setting, remove the cap on the bulb and turn
the adjustment screw clockwise. To lower the setting, turn the
screw counterclockwise. Do not force the adjustment beyond
the range it is designed for as this will damage the adjustment
assembly. The regulating valve opening point can be
determined by slowly reducing the system load 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.
A solenoid valve is located ahead of the bypass valve and is
controlled by the MicroTech III controller. It is active when the
first stage of cooling on a circuit is active.
VFD Low Ambient Control (Optional)
The optional VFD fan control is used for unit operation below
32
o
F (0
o
C) down to a minimum of -10
o
F (-23.3
o
C). The control
looks at the saturated discharge temperature and varies
(pressure) at the "target" temperature. This temperature is
established as an input to a setpoint screen labeled "Sat
Condenser Temp Target."
Compressor Communications
The communication module, installed in the 20 to 40 ton
compressor electrical box, provides advanced diagnostics,
protection, and communications that enhance compressor
performance and reliability.
Features include motor temperature protection, scroll
temperature protection, missing phase protection, reverse
phase protection, low control circuit voltage protection, short
cycling detection and alert, modbus communication to system
controller, operational and fault history storage, and LED
status display.
Operation
Warnings and Alerts
A
solid
g
reen LED
indicates the module is powered and
operation is normal.
A
solid red LED
indicates an internal problem with the
module.
A
flashing green LED
communicates
Warning
codes.
Warning codes do not result in a trip or lockout condition.
A
flashing red LED
communicates
Alert
codes.
Alert
codes
will result in a trip condition and possibly a lockout condition
Warning Codes (Flashing Green LED )
Code 1 – Loss of Communication: The module will flash the
green
Warning
LED one time indicating the module has not
communicated with the master controller for longer than 5
minutes.
Code 2 – Reserved For Future Use
Code 3 – Short Cycling: The module will flash the green
Warning
LED three times indicating the compressor has short
cycled more than 48 times in 24 hours.
Code 4 – Open/Shorted Scroll Thermistor: The module will
flash the green
Warning
LED four times indicating an open/
shorted
WARNING
The hot gas line may become hot enough to cause injury. Be
careful during valve checkout.