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Control wiring for units with constant airflow ECM blower
motors is routed through a constant airflow ECM interface board.
Thermostat input wiring is connected to the 10-pin screw type
terminal block on the lower center portion of the ECM Interface
Board. In addition to providing a connecting point for thermostat
wiring, the interface board also translates thermostat inputs into
control commands for the Electronic Commutated Motor (ECM)
DC fan motor and displays an LED indication of operating status.
Refer to the unit wiring diagrams for complete details. See Fig. 34.
The thermostat connections and their functions are as follows.
ECM INTERFACE THERMOSTAT CONNECTIONS
•
Y1 First Stage Compressor Operation
•
Y2 Second Stage Compressor Operation
•
G Fan
•
O Reversing Valve (energized in cooling)
•
W1 Auxiliary Electric Heat (runs with compressor)
•
EM/W2 Emergency Heat (electric heat only)
NC Transformer 24 VAC Common (extra connection)
•
•
C1 Transformer 24 VAC Common (primary connection)
R Transformer 24 VAC Hot
•
•
H Dehumidification Mode
10
R
R
C1
C2
EM
W2
W1
W1
O
Y2
O
Y1
Y2
G
H
Y1
C
G
C G
R
9
8
6
7
LEGEND
1
Motor harness plug
2
Blower CFM adjustment
3
Motor settings
4
Dehumidification indication
5
Thermostat digital contact inputs
6
CFM count indicator
7
Thermostat input status indication
8
Reheat digital outputs
9
Thermostat outputs
10
24 VAC
11
Dehumidification method selector
Fig. 34 — ECM Interface Board Physical Layout
THERMOSTAT AND DDC SENSORS
Thermostats or DDC space sensors should be located on an
interior wall away from supply ducts. Avoid locations subject to
direct sunlight or drafts, or external walls. Thermostat wiring
should be 18 AWG (American Wire Gauge). Refer to the
installation instructions for the thermostat for further details.
IMPORTANT: Exceptionally long runs of thermostat wire
should be avoided to prevent voltage drops in the control circuit.
HOT GAS REHEAT CONTROL
Units with hot gas reheat (HGRH) will include an additional H
terminal on the input terminal board for dehumidification con-
trol. To enable a call for dehumidification, a 24V signal must
be sent to the H terminal with no voltage applied to the Y1 or
1
3
J01
CFM
CFM
ADJUST
A
NORM
B
[+]
C
[-]
TEST
D
H
HGRH
YES
HGRH
O Y1 Y2 W1 W2 H
C
2
5
4
O terminals. Any call for cooling (Y1 and O) will override the
dehumidification call.
AUXILIARY RELAY (DELUXE D ONLY)
All units with Deluxe D control include an auxiliary relay that can
be field wired to enable a field provided loop pump or solenoid
valve when there is a call for compressor operation. (See Fig. 15.)
ENERGY MANAGEMENT SWITCH (DELUXE D ONLY)
All units with Deluxe D control include an energy management
switch (EMS) relay that can be field wired to disable unit
operation when a 24V signal is removed from the relay. Removing
the 24V signal causes the relay to open, which cuts 24V power to
the unit control circuit. All unit components will be disabled at
when the EMS is deactivated. (See Fig. 15.)
NOTE: Units with constant torque ECM motors may experience a
30 second delay between when the EMS is activated and when the
blower finally shuts off. Constant torque ECM blowers are factory
programmed with a 30 second delay when losing the control
signal, to prevent nuisance shut downs.
BOILERLESS HEAT CONTROL (DELUXE D ONLY)
All units with Deluxe D control include a boilerless heat relay that
can be field wired to enable an external heat source when the
water loop temperature drops below the boilerless heat control set
point. (See Fig. 15.)
ALARM OUTPUT (ALL UNITS)
If the unit is being connected to a thermostat or DDC control with
an alarm indicator, this connection is made at the unit malfunction
output on the Unit Protection Module (UPM). See the Unit
Protection Module heading in the Set Up Unit Controls section for
further details.
WSHP OPEN CONTROL
WSHP Open is a factory installed DDC control that requires
the use of Carrier ZS or WS sensors or the Carrier Equipment
NO
Touch or System Touch for space temperature sensing. WSHP
Open is not compatible with thermostats or third party
temperature sensors.
All WSHP Open wiring is completed at the WSHP Open control
11
board. See Fig. 29 for details. For further instructions on WSHP
Open, please visit HVACPartners.com or Carrier.com for the
WSHP Open V4 Integration Guide and Points/Properties Guide.
CONTROL TRANSFORMER
All units with the Better B control package include a 75VA
transformer and are not available with the HGRH or waterside
economizer options. All units with Complete C control and
without HGRH or waterside economizer include a 50VA
transformer. All units with Complete C control and with HGRH or
waterside economizer use a 75VA transformer. All units with
Deluxe D control or WSHP Open include a 75VA transformer.
Exceeding the transformer capacity can result in low control
voltage, erratic unit operation or damage to the heat pump.
The VA capacity of the transformer should be considered when
applying low voltage accessories, such as shut off valves,
thermostats, or DDC controls. Table 8 shows the VA draw of
factory-mounted components in the low voltage heat pump. The
total VA draw of the heat pump internal components plus any at-
tached accessories must be lower than the VA capacity of the unit
control transformer.
34
CAUTION
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