Carrier ComfortLink HXC076 Controls, Start-Up, Operation, Service, And Troubleshooting Download Page 12

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The control will use the higher of the 2 Saturated Condens-

ing Temperature values for 30GXN,R080-160 units. For the
30GXN,R153, 163-350 units, each circuit’s fan stages are
independently controlled based on the circuit's Saturated
Condensing Temperature. Refer to Table 9 for condenser fan
staging information.
WATER-COOLED UNITS (30HXC) — The 30HXC chiller
can be configured to control direct acting water valves that are
controlled by a 4 to 20 mA (2 to 10 vdc) signal. A 0 to 20 mA
(0 to 10 vdc) or 20 to 0 mA (10 to 0 vdc) can also be config-
ured. Installing a 500-ohm

watt resistor across the 2 output

terminals of the mA signal enables the use of the vdc signal.
Set this configuration (VHPT, configuration mode under
sub-mode OPT1) to 1 (4 to 20 mA or 2 to 10 vdc), 2 (0 to
20 mA or 0 to 10 vdc), or 3 (20 to 0 mA or 10 to 0 vdc) as
desired depending on valve type. Signal connections are made
at terminal block TB2, terminals 14 and 15. The control
scheme reads the saturated condensing temperature and uses a
PID (proportional integral derivative) loop to control the head
pressure. Proportional, Integral and Derivative gain parameters
for the water-cooled controls are adjustable and can be found in
the SERV sub-mode under the Configuration mode. Only certi-
fied Carrier Comfort Network technicians should perform
checkout and adjustment of the PID loop.
CONDENSERLESS UNITS (30HXA) — The 30HXA unit is
often applied with an 09DK air-cooled condenser. The remote
condenser fans are controlled by 2 relay outputs. These
connections are in the 30HXA control box. See Field Wiring
section on page 72 for wiring details. The 30HXA control must
be configured to turn the 09DK fans on and/or off. To set the
30HXA control for this configuration, Unit Type (TYPE,
Configuration mode under sub-mode UNIT) must be config-
ured to 3 (Split System). The Head Pressure Control Type

(HPCT under sub-mode OPT1) must be configured to 1 (air-
cooled), and Condenser Pump control must be set to 0 (CNPC
must be set to No control, Configuration mode under sub-mode
OPT1).

Low ambient head pressure control can be accomplished

with fan cycling pressure switches (09DK054-094), tempera-
ture switches (09DK044, 074-094), and Motormaster®
control. The Motormaster control requires a temperature sensor
input to control condenser fan cycling. The Motormaster V
control also requires a temperature sensor input or the 4 to
20 mA output signal from the

Comfort

link™ control system.

See accessory installation instructions for further information.

The Head Pressure Control Type (HPCT under sub-mode

OPT1) may be set to control various types of head pressure
control devices. HPCT may be set to 0 (No Control), 1
(Air Cooled), 3 (Common Condenser), or 4 (Independent
Condenser).

The 30HXA chillers also support the use of a 4 to 20 mA

(2 to 10 vdc), 0 to 20 mA (0 to 10 vdc), or 20 to 0 mA (10 to
0 vdc) for fan speed control. Installing a 500-ohm

watt

resistor across the 2 output terminals of the mA signal enables
the use of the vdc signal. Set this configuration (VHPT, config-
uration mode under sub-mode OPT1) to 1 (4 to 20 mA or 2 to
10 vdc), 2 (0 to 20 mA or 0 to 10 vdc), or 3 (20 to 0 mA or 10
to 0 vdc) as desired depending on control type. For common
output applications (single output for both circuits), the signal
connections are made at terminal block TB2, terminals 14 and
15. For independent (one output for each circuit) applications,
the signal connections are made at terminal block TB2, termi-
nals 14 and 15 for circuit A, and terminals 12 and 13 for
circuit B.

Table 6 — Field Configured Head Pressure Control Options

*A vdc signal can be generated by installing a 500-ohm

-watt resistor across the 2 output terminals of the mA signal.

UNIT

CONFIGURATION OPTION

DESCRIPTION

POINT NAME

FACTORY CONFIGURATION

30GX

Head Pressure Control Type

Method of controlling head
pressure

HPCT