55
pressure output is designed for use with non-grounded control-
lers with a maximum input impedence of 500 ohms.
NOTE: It is up to the site design engineering agent to integrate
this analog output with any external system device(s) to pro-
duce the desired effect. Carrier does not make any claim that
this output is directly usable to control any specific piece of
equipment (that is, without further control elements or signal
conditioning), although it may be.
The head pressure reference output will be on whenever the
condenser pump is operating. It may also be manually operated
in CONTROLS TEST. When the head pressure differential is
less than the value entered for DELTA P AT 0%, the output will
be maintained at 4 mA. The output is 2 mA when the chiller is
not running.
LEGEND
P—Condenser Pressure-
Cooler Pressure
T—ECL-LCL
ECL — Entering Chilled
Liquid Temperature
LCL — Leaving Chilled
Liquid Temperature
HGBP — Hot Gas Bypass
Fig. 31 — 23XRV Hot Gas Bypass
Option 1 (English)
DEFAULT VALUES:
POINT HFC-134A
T
1
1.5
P
1
150
T
2
4
P
2
200
a23-1608
Fig. 32 — 23XRV Hot Gas Bypass Option 1 (SI)
LEGEND
P
—
Condenser Pressure-
Cooler Pressure
T—ECL-LCL
ECL — Entering Chilled
Liquid Temperature
LCL — Leaving Chilled
Liquid Temperature
HGBP — Hot Gas Bypass
DEFAULT VALUES:
POINT HFC-134A
T
1
0.8
P
1
1034
T
2
2.2
P
2
1379
a23-1609
Minimum Speed
+ HGBP ON
DELTA SPEED
Minimum Speed + HGBP ON
DELTA SPEED + HGBP OFF
DELTA SPEED
HGBP
Off
HGBP
On
HGBP Off As VFD TARGET
SPEED Decreases
HGBP On As VFD TARGET
SPEED Increases
DELTA SPEED
ΔP
Fig. 33 — Hot Gas Bypass Option 2
LEGEND
P—Condenser Pressure –
Evaporator Pressure
HGBP — Hot Gas Bypass
NON-ZERO
EXAMPLE
OF
MINIMUM HEAD
PRESSURE REFERENCE
OUTPUT
DELTA P
AT 100%
DELTA P
AT 0%
DELTA P
0 mA 2 mA
4 mA
(0%)
20 mA
(100%)
4 T0 20 mA OUTPUT
Fig. 34 — Head Pressure Output
Reference Control
a23-1610
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