Ecm Blower Control - Carrier 50YFV Installation, Operation And Maintenance Instructions

R e s i d e n t i a l D i g i t a l P a c k a g e d U n i t s G T- P B S e r i e s - 6 0 H z P u r o n
R e v : 4 A p r i l , 1 4

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 Two-Way Unit Communicating
System communicating multi-stage thermostat should be
used (ATC32U**).
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 (ATC32U**) or diagnostic tool
(ACDU**). 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
Table 9. 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 necessary to use the ATC32U** communicating
thermostat to engage the Auto Dehumidifi cation feature on
units with Internal Flow Controllers. Units with Internal Flow
Controllers utilize the 'H' terminal on the DXM2 as an input
for an ambient temperature switch. Units without the Internal
Flow Controller option use the 'H' terminal on the DXM2
controller to initiate the Auto Dehumidifi cation mode. Refer to
the DXM2 AOM for more information (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 duration of the "ramp down" periods are adjustable from
0 seconds to 255 seconds. This adjustment is available
in the Aifl ow Selection screen using the communicating
thermostat or confi guration/diagnostics tool, see Figure 27.
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Special Note for AHRI Testing: To achieve rated airfl ow for
AHRI testing purposes, it is necessary to change the CFM
settings to rated airfl ow.
Figure 29: Airfl ow Confi guration Screen on
Communicating Thermostat
AIRFLOW SELECTION
HEAT STAGE 1
HEAT STAGE 2
AUXILIARY HEAT
EMERGENCY HEAT
COOL STAGE 1
COOL STAGE 2
COOL DEHUMID 1
COOL DEHUMID 2
CONTINUOUS FAN
HEAT OFF DELAY
COOL OFF DELAY
PREVIOUS
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CFM
600
750
850
850
525
700
425
550
350
60
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