14
ECM INTERFACE BOARD
Refer to Fig. 7, item (12) for ECM interface board location. 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 provides thermostat signals to unit’s UPM board. The
thermostat connections and their functions are as follows:
10
1
2
7
8
9
5
11
4
6
3
A14124
(1) Motor Harness Plug
(7) Thermostat Input Status Indication
(2) Blower CFM Adjustment
(8) Reheat Digital Outputs
(3) Motor Settings
(9) Thermostat Outputs
(4) Dehumidification Indication
(10) 24 VAC
(5) Thermostat Contact Inputs
(11) Dehumidification Method Selector
(6) CFM Count Indicator
Fig. 13 -- ECM Interface Board
NOTE
:
CFM LED indication is an approximation. Utilize
conventional Test and Balance equipment for accurate airflow
measurement.
S
CFM count indicator (see Fig. 13, item 6) blinks to indicate
approximate airflow in CFM and may flicker when the unit is off.
S
Each blink of the LED represent approximately 100 CFM of air
delivery so if the LED blinks 12 times, pauses, blinks 12 times,
etc. the blower is delivering approximately 1200 CFM.
Dehumidification Mode
Position the HGRH DIP switch in the “NO” (OFF) position.
When the switch is in this position, upon a dehumidification call,
the unit will operate at a lower speed to increase dehumidification
while cooling. See Fig. 14.
A14126
Fig. 14 -- Dehumidification Method Selector
Thermostat Outputs
Dry Contact Left side terminal strip in the stat, D1, D2
YI
First Stage Compressor Cool
Y/Y2
Second Stage Compressor Cool
W1
Auxiliary Electric Heat
(runs in conjunction with compressor)
W2/E
Emergency Heat (electric heat only)
O
Reversing Valve (energized in cooling)
G
Fan
R
Transformer 24 VAC Hot
C
Transformer 24 VAC Common
NOTE
: When unit is used with Carrier and Bryant thermostats
with Relative Humidity Control (Carrier Edge TP--PRH or
TP--NRH / Bryant Preferred T6--PRH or T6--NRH), the unit’s
dehumidification mode is in reverse logic and will not activate
dehum unless a relay, as shown in Fig. 15, is used. A simplified
explanation of the reverse logic follows.
RH
ECM
Stat Logic:
Board Logic:
No Dehum Demand: Dh -- energized
Dh--not energized
Dehum Demand:
Dh -- de--energized
Dh -- energized
Y1
Y2
W 1
O
G
R
C
LOW VOLTAGE CLASS II WIRING – 18AWG
W 2
24V INPUTS
BLOWER
REVERSING VALVE
HEATING STAGE 1
COOLING STAGE 2
COOLING STAGE 1
HEATING STAGE 2
ECM CONTROLLER INTERFACE
S
T
L
O
V
E
N
I
L
C
A
V
4
2
EX: 230VAC
H
Y1
Y2
W 1
O/B
G
R
C
24VAC (HOT)
24VAC (COMMON)
BLOWER
SWITCH OVER VALVE
W 2/E
HEATING STAGE 2
24V OUTPUTS
HEATING STAGE 1
COOLING STAGE 2
COOLING STAGE 1
Dry
Contact
THERMOSTAT
HUMIDISTAT
DE-HUMIDIFICATION CALL
HGRH
YES NO
DHR – DEHUMIDIFICATION RELAY
FIELD INSTALLED
C
RELAY
A150487
Fig. 15 -- Cool to Dehumidify Application for Thermostats with Dehumidification
(Not required for Cor / Housewise thermostats)
