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Operating Procedures
Table 22. Hot gas low balancing control
Screen
Hot Gas Bypass
Valves Control
Hot Gas Bypass
Valve Setup
Hot Gas Bypass
Valves Manual
Control
Low-Lift Application
The low-lift application uses a special expanded-map
compressor with a refrigerant motor cooling pump. With a
standard lift compressor, motor cooling is dependent on a
pressure of 1.5 or better to push liquid refrigerant into the
cooling ports of the compressors. In Low-Lift, the
refrigerant pump pushes the liquid refrigerant into the
cooling ports allowing for the chiller to drop the pressure
ratio to ~1. This low-pressure ratio leads to near free-
cooling efficiencies.
This function is enabled by mode selection.
1. Disabled – No operation.
2. Motor Cooling – Function provides cooling to
compressor motor only.
3. Split System – Function provides both motor cooling
and flow boost to EXV.
58
User Interface
Function
•
Displays trend and current values for Setpoint,
Process Value and Valve position.
•
PV. Chiller LWT.
•
SP. SP = Chiller SP – low urgency zone (refer
to Chiller Control Manual) + SP Offset
(described below).
•
T3C dP. Evaporator inlet / outlet pressure delta.
•
Trend has y-axis zoom capability.
•
Provides access to other pop-up screens:
–
Setup
–
HGVs
–
Solenoids
•
SP Offset. Involved in setpoint calculation (see
main screen SP description above)
•
P-Gain and I PID constants.
Each Hot Gas Bypass valve can be in one of the
following modes:
•
Auto. Valve controlled automatically by Hot
Gas Bypass PID controller (solenoid opens
when PID opens the modulating valve)
•
Off. Valve is always off;
•
Manual. Valve position is set up manually.
This section focuses on the motor cooling mode of the low-
lift application. In this mode, the controller looks at the
pressure ratio and uses a threshold setpoint to enable the
function as a permissive. The refrigerant pump is controlled
by the same threshold values that the compressor uses to
open its own motor cooling valves.
Inputs
•
Compressor pressure ratio
•
Inverter Temperature
•
Cavity Temperature
•
Compressor Run. – Compressor must be running to
use this function.
Parameters
•
Pressure Ratio Threshold – If the pressure ratio
drops below this value, then this permissive is satisfied.
There is a built-in hysteresis of 0.2.
Access
Main Menu >
Devices Menu
> HGV
Main Menu >
Devices Menu
> HGV button
> Setup
button.
Main Menu >
Devices Menu
> HGV button
> HGVs
button.
ARTC-SVX014A-EN
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