Comfort-Aire WDG Air Handler Series - Manual (Page 14)

14
Installation, Operation & Maintenance WDG AIR HANDLER SERIES Heat Controller, LLC
ECM Blower Control
The ECM fan is controlled by an interface board that converts
thermostat inputs and fi eld selectable CFM settings to signals
used by the ECM motor controller. Units manufactured before
July 2005 have version I (P/N 69243707). Units manufactured
after July 2005 have version II (P/N 17B0019N01). Fan speeds
are selected with jumpers for version I or via a nine position DIP
switch for version II. To take full advantage of the ECM motor
features, a multi-stage thermostat should be used (2-stage
heat/2-stage cool or 3-stage heat/2-stage cool).
HFC-410A packaged units built after May 2009 have ECM
controller version III (P/N 17B0034N02). This controller includes
logic and a relay to control.
Note: Power must be off to the unit for at least three seconds
before the ECM motor will recognize a speed change.
The motor will recognize a change in the CFM Adjust or
dehumidifi cation mode settings while the unit is powered.
There are four different airfl ow settings from lowest airfl ow rate
(speed tap 1) to the highest airfl ow rate (speed tap 4). The charts
below indicate settings for both versions of the ECM interface
board, followed by detailed information for each setting.
Cooling Settings: The cooling setting determines the cooling
(normal) CFM. Cooling (normal) setting is used when the unit is
not in dehumidifi cation mode. Tap 1 is the lowest CFM setting,
while tap 4 is the highest CFM setting. To avoid air coil freeze-up,
tap 1 may not be used if the dehumidifi cation mode is selected.
Consult submittal data or specifi cations catalog for the specifi c unit
series and model to correlate speed tap setting to airfl ow in CFM.
Heating Settings: The heating setting determines the heating
CFM. Tap 1 is the lowest CFM setting, while tap 4 is the highest
CFM setting. Consult submittal data or specifi cations catalog for
the specifi c unit series and model to correlate speed tap setting to
airfl ow in CFM.
Auxiliary/Emergency Heat Settings: The auxiliary/emergency
heat setting determines the CFM when the unit is in auxiliary
heat or emergency heat mode. This setting is used for residential
units with internal electric heat. When auxiliary electric heat is
energized (i.e. compressor and electric heat), the greater of the
auxiliary/emergency or heating setting will be used. A “G” (fan)
signal must be present from the thermostat for electric heat to
operate. Consult the submittal data or specifi cations catalog for
the specifi c unit series and model to correlate speed tap setting to
airfl ow in CFM.
CFM Adjust Settings: The CFM adjust setting allows four
selections. The NORM setting is the factory default position. The
+ or – settings adjust the airfl ow by +/- 5%. The +/- settings are
used to “fi ne tune” airfl ow adjustments. The TEST setting runs the
ECM motor at 400 CFM/nominal ton at a constant CFM. Example:
WDG024 = 800 CFM.
Dehumidifi cation Mode Settings: The dehumidifi cation mode
setting provides fi eld selection of humidity control. When
operating in the normal mode, the cooling airfl ow settings
are determined by the cooling tap setting above. When
dehumidifi cation is enabled there is a reduction in airfl ow in
cooling to increase the moisture removal of the heat pump.
Consult submittal data or specifi cations catalog for the specifi c
unit series and model to correlate speed tap to airfl ow in CFM.
The dehumidifi cation mode can be enabled in two ways.
1. Constant Dehumidifi cation Mode: When the dehumidifi cation
mode is selected (via DIP switch or jumper setting), the ECM
motor will operate with a multiplier applied to the cooling
CFM settings (approx. 20-25% lower airfl ow). Any time the
unit is running in the cooling mode, it will operate at the lower
airfl ow to improve latent capacity. The “DEHUM” LED will
be illuminated at all times. Heating airfl ow is not affected.
NOTE: Do not select dehumidifi cation mode if cooling setting
is tap 1.
2. Automatic (Humidistat-controlled) Dehumidifi cation Mode:
When the dehumidifi cation mode is selected (via DIP switch
or jumper setting) AND a humidistat is connected to terminal
DH (version II) or HUM (version I), the cooling airfl ow will
only be reduced when the humidistat senses that additional
dehumidifi cation is required. The DH (or HUM) terminal is
reverse logic. Therefore, a humidistat (not dehumidistat)
is required. The “DEHUM” LED will be illuminated only
when the humidistat is calling for dehumidifi cation mode.
Heating airfl ow is not affected. NOTE: Do not select
dehumidifi cation mode if cooling setting is tap 1.