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Step 10 — Operate ECM Interface Board
STANDALONE — NO DDC CONTROLS — The ECM
fan is controlled by an interface board that converts thermostat
inputs and field selectable cfm settings to signals used by the
ECM (electronically commutated motor) controller. See
Fig. 32.
NOTE: Power must be off to the unit for at least three seconds
before the ECM will recognize a speed change. The motor will
recognize a change in the CFM Adjust or Dehumidification
mode settings while the unit is powered.
There are four different airflow settings from lowest airflow
rate (speed tap 1) to the highest airflow rate (speed tap 4).
Tables 9-13 indicate settings for the ECM interface board, fol-
lowed by detailed information for each setting.
Cooling
— The cooling setting determines the cooling (nor-
mal) cfm for all units with ECM motor. Cooling (normal) set-
ting is used when the unit is not in Dehumidification mode. Tap
1 is the lowest cfm setting, while tap 4 is the highest cfm set-
ting. To avoid air coil freeze-up, tap 1 may not be used if the
Dehumidification mode is selected. See Table 9.
Table 9 — Cooling Settings
Heating
— The heating setting determines the heating cfm
for 50PTH,PTV,PTD units. Tap 1 is the lowest cfm setting,
while tap 4 is the highest cfm setting. See Table 10.
Table 10 — Heating Settings
CFM Adjust
— The CFM Adjust setting allows four selec-
tions. The NORM setting is the factory default position. The +
or – settings adjust the airflow by ±15%. The + or – settings are
used to “fine tune” airflow adjustments. The TEST setting runs
the ECM at 70% torque, which causes the motor to operate
like a standard PSC motor, and disables the cfm counter. See
Table 11.
Table 11 — CFM Adjust Settings
Dehumidification Mode
— The dehumidification mode
setting provides field selection of humidity control. When op-
erating in the normal mode, the cooling airflow settings are de-
termined by the cooling tap setting in Table 12.
Table 12 — Dehumidificaton Mode Settings
When dehumidification is enabled, there is a reduction in
airflow in cooling to increase the moisture removal of the heat
pump. The Dehumidification mode can be enabled in two
ways:
1. Constant Dehumidification mode: When the Dehumidifi-
cation mode is selected via DIP switch, the ECM will
operate with a multiplier applied to the cooling CFM
settings (approximately 20 to 25% lower airflow). Any
time the unit is running in the Cooling mode, it will oper-
ate at the lower airflow to improve latent capacity. The
“DEHUM” LED will be illuminated at all times. Heating
airflow is not affected.
NOTE: Do not select Dehumidification mode if cooling
setting is tap 1.
2. Automatic (humidistat-controlled) Dehumidification
mode: When the Dehumidification mode is selected
via DIP switch AND a humidistat is connected to termi-
nal DH, the cooling airflow will only be reduced when
the humidistat senses that additional dehumidification is
required. The DH terminal is reverse logic. Therefore,
a humidistat (not dehumidistat) is required. The
“DEHUM” LED will be illuminated only when the hu-
midistat is calling for Dehumidification mode. Heat-
ing airflow is not affected.
NOTE: Do not select Dehumidification mode if cooling
setting is tap 1.
CAUTION
When the disconnect switch is closed, high voltage is pres-
ent in some areas of the electrical panel. Exercise caution
when working with energized equipment.
TAP SETTING
DIP SWITCH
SW1 SW2
1 ON ON
2 ON OFF
3 OFF ON
4 OFF OFF
TAP SETTING
DIP SWITCH
SW3 SW4
1 ON ON
2 ON OFF
3 OFF ON
4 OFF OFF
TAP SETTING
DIP SWITCH
SW7 SW8
TEST ON ON
ON OFF
OFF ON
NORM OFF OFF
–
+
TAP SETTING
DIP SWITCH
SW9
NORM ON
Dehumid OFF
Y
GGGGR
W
O
Y2
Y1
G
R
C
Y2
Y1
G
O
W
C
R
DH
AL1
A
A
AL1
SW1
SW2
SW3
SW4
SW5
SW6
SW7
SW8
SW9
OFF
ON
G
DEHUM
CFM
TB1
J1
S1
THERMOSTAT
INPUT LEDS
CFM COUNTER
1 FLASH PER 100 CFM
ECM MOTOR
LOW VOLTAGE
CONNECTOR
1/4" SPADE
CONNECTIONS
TO COMPLETE C OR
DELUXE D BOARD
THERMOSTAT
CONNECTIONS
DEHUMIDIFICATION
LED
FAN SPEED SELECTION DIP SWITCH
Fig. 32 — ECM Interface Board Physical Layout