Comfort-Aire HEH Series 2 to 5 Tons - Manual (Page 27)

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Heat Controller, LLC. HEV/H SERIES Installation, Operation & Maintenance
ECM BLOWER CONTROL
The ECM fan is controlled directly by the DXM2 control board
that converts thermostat inputs and CFM settings to signals
used by the ECM motor controller. To take full advantage of
the ECM motor features, a communicating thermostat should
be used.
The DXM2 control maintains a selectable operating airfl ow
[CFM] for each heat pump operating mode. For each
operating mode there are maximum and minimum airfl ow
limits. See the ECM Blower Performance tables for the
maximum, minimum, and default operating airfl ows.
Airfl ow levels are selected using the confi guration menus
of a communicating thermostat or diagnostic tool. The
confi guration menus allow the installer to independently
select and adjust the operating airfl ow for each of the
operating modes. Air fl ow can be selected in 25 CFM
increments within the minimum and maximum limits shown
in the ECM Blower Performance Table. The blower operating
modes include:
• First Stage Cooling (Y1 & O)
• Second Stage Cooling (Y1, Y2, & O)
• First Stage Cooling in Dehumidifi cation Mode
(Y1, O, & Dehumid)
• Second Stage Cooling in Dehumidifi cation Mode
(Y1, Y2, O, & Dehumid)
• First Stage Heating (Y1)
• Second Stage Heating (Y1 & Y2)
• Third Stage (Auxiliary) Heating (Y1, Y2, & W)
• Emergency Heating (W with no Y1 or Y2)
• Fan (G with no Y1, Y2, or W)
It is highly recommended that communicating thermostat
or service tool be used to set dehumidifi cation mode
electronically. For dehumidifi cation settings on other units
using the non-communicating stat, refer to DXM2 AOM (part
#97B0003N15).
The ECM motor includes “soft start” and “ramp down”
features. The soft start feature is a gentle increase of motor
rpm at blower start up. This creates a much quieter blower
start cycle.
The ramp down feature allows the blower to slowly decrease
rpm to a full stop at the end of each blower cycle. This
creates a much quieter end to each blower cycle and adds
overall unit effi ciency.
The ramp down feature is eliminated during an ESD
(Emergency Shut Down) situation. When the DXM2 ESD
input is activated, the blower and all other control outputs are
immediately de-activated.
The ramp down feature (also known as the heating or cooling
“Off Delay”) is fi eld selectable by the installer. The allowable
range is 0 to 255 seconds.