Vertiv Liebert PDX - EconoPhase Operation Details; System Operating Modes; EconoPhase Control Parameters

6
Liebert
®
PDX, EconoPhase Version - UM - 265133 - 29.08.2019
1.8 - Description of Liebert
®
EconoPhase Operation
The Liebert
®
EconoPhase unit enables the Liebert
®
PDX system
to operate in any of three modes to control temperature, depending
on the outdoor temperature and the load.
• Compressor Mode
• Pump Mode
• Mixed Mode
When the outdoor temperature becomes low enough to provide
the required temperature di󰀨erence between the inside air and
the outside air, there is no need to compress the refrigerant to a
higher pressure/temperature. When the outdoor temperature is
low enough, the system switches from Compressor Mode to Pump
Mode or to Mixed Mode.
• Compressor Mode: All available compressors may be used
to maintain the control temperature. All the available Liebert
®
EconoPhase pumps are O󰀨. The control will typically run in
this mode when the load and temperatures are such that full
or partial Liebert
®
EconoPhase operation is not possible, or
because certain pumps have experienced alarms.
• Pump Mode: All of the available pumps may be used to
maintain the Control Temperature. All the compressors in the
system are O󰀨. The control will typically run in this mode when
load and temperatures permit.
• Mixed Mode: The pump in Circuit 1 is On and the compressor(s)
in Circuit 2 is On. Some systems may not have Mixed Mode
capability, depending on the manufacture date. Contact the
factory to inquire about a software upgrade.
1.8.1 EconoPhase Control
EconoPhase operation has three main controlled parameters:
• return or supply air temperature control
• refrigerant temperature
• pump pressure di󰀨erential (outlet pressure - inlet pressure)
Room Temperature
When the system is in Pump Mode, the room temperature is
controlled by modulating the pump speed with a variable frequency
drive. The load requirement will determine if one pump or two
are needed. Figure 8 shows the sequence of operation in terms
of pump speed. Minimum speed is 45% and maximum speed is
100%. See Table 2 for more detail on the events shown in Figure 8
and the conditions that trigger action.
The pump startup routine calls for a start speed of 80%. The pump
will run for up to 60 seconds at 80% with the EEV at 60% while
waiting on the pump pressure di󰀨erential to reach at least 0.83 bar
to indicate that ow has been established. If the pump establishes
ow, the speed will change from 80% to the required control speed
as shown on the curves in Figure 6.
Fig.6 - Two-circuit pump control
E
I
C
H
F
K
J
A
B
100%75%55%40%20%0
Minimum
Pump
Speed
Maximum
Pump
Speed
Pump
Speed
y
x
Capacity
Pump 2
L
G
D
Pump 1
Pump 2 under manual control
Pump 2 under PID control
Pump 1 under manual control
Pump 1 under PID control