Ingersoll-Rand ReliaTel, Manual, Page: 61 / 176

RT-SVD03L-EN 61
Multi-Speed PWM Controlled Indoor Fan
with Dual Capacity Compressor
This control scheme will cover 17 SEER 3 to 5 ton
Precedent
™
units equipped with a PWM controlled
indoor fan motor for multi-speed control and a dual
capacity compressor.
Configuration
Units equipped with a PWM controlled indoor fan
motor and a dual capacity compressor will be
configured uniquely within the ReliaTel
™ system by
being configured as a non-heat pump, two compressor
unit with two step cooling and the RTRM J9-4 closed to
24VAC. Also, the RTOM J4-3 will be closed to ground
for PWM control.
Unit Operation for Multi-Speed PWM
Controlled Indoor Fan
Unit operation for Multi-Speed PWM controlled indoor
fan units will be similar to the control of standard two
compressor, two step cooling units with the exception
of the multi-speed characteristics of the PWM
controlled indoor fan motor and special handling
required for the dual capacity compressor. For indoor
fan control, the supply fan will follow the airflow
profiles as described in the following sections during
all active cooling modes. During all active heating
modes, the unit will utilize full indoor fan speed based
on the selected maximum fan speed.
Airflow Profiles
Figure 49. Airflow staging
ShortRu
Short
OffDelayT
Off
Rating
RatingT
STAGE 1
STAGE 2
The following airflow profile table will be used in
determining the PWM output signal for the associated
cooling stages.
Table 19. Airflow profiles
PWM
Mode
Short
Run
Time
Short
Run
Fan
Out-
put%
Rating
Run
Time
Rating
Out-
put%
Off
Delay
Time
Off
Delay
Signal
%
Stage 1 Operation
1st Stage
Airflow
7.5
mins
57%
Any
70%
160
secs
50%
Table 19. Airflow profiles (continued)
PWM
Mode
Short
Run
Time
Short
Run
Fan
Out-
put%
Rating
Run
Time
Rating
Out-
put%
Off
Delay
Time
Off
Delay
Signal
%
Compressor
Output at
1st Stage
7.5
mins
67%
Any
67% 0%
Stage 2 Operation
2nd Stage
Airflow
7.5
mins
82%
Any
100%
160
secs
50%
Compressor
Output at
2nd Stage
7.5
mins
100% Any 100% 0%
Note: The rating output % refers to the maximum fan speed signal
as a percentage of the user selected unit maximum airflow
that will be applied to the indoor fan for the duration of time
that the unit runs at the associated compressor stage.
High Fan Speed Selection
Each motor program will include an upper CFM
setpoint and the user will then have the ability to adjust
the DACSP onboard potentiometer located on the
RTOM to select the proper unit/application specific
maximum airflow. At the maximum (full clockwise on
the potentiometer), ReliaTel™ will output 100% of the
maximum PWM signal from the RTOM indoor fan
speed output (J11 - 2,1) for control. At the minimum
(full counterclockwise), ReliaTel™ will output 70% of
the maximum PWM signal for control. Once a
maximum value is selected via the onboard
potentiometer, ReliaTel™ will control the indoor fan
speed to the previously described airflow profiles
utilizing the maximum set value as the reference point
(100% rating) for all percentages.
Fan Only Operation
When the RTRM receives a call for fan only mode, the
unit will energize the RTRM supply fan output and the
RTOM will begin to output a PWM signal at 50% of the
high stage airflow PWM signal and remain there for the
duration of the call.
Fan Off Delay (from Cooling)
When the supply fan is commanded off due to no call,
the supply fan will ramp down to a signal that is 50% of
the high stage airflow PWM signal and will remain
energized at that speed for a total of 160 seconds.
Cooling Operation
For cooling operation the unit will utilize normal
ReliaTel
™ cooling control schemes for a two
compressor unit, but instead of each compressor
output being connected to an independent
compressor, they will be connected to the dual capacity
compressor for control. The compressor 1 output
signal will energize the dual capacity compressor and
operate it at 67% of its total capacity. The compressor 2
output signal is connected to a solenoid on the
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