Time Delays; Outdoor Temp (Dc Volts, Tolerance +/- 2%) - Bryant Base Series Application Manual And Service Manual

Residential Air Conditioners and Heat Pumps Using R-22 and Puron® Refrigerant: Application Guideline and Service Manual
The PWM is called a 20 percent duty cycle signal. If the on time is
increased to 4 sec of the 5 sec period, the PWM is called an 80 percent
duty cycle. The ECM reads the PWM signal and increases the motor
speed linearly from minimum speed to maximum speed with the percent
duty cycle value of the supplied PWM signal.
Outdoor Fan Motor Operation
There are two different types of motors used in the Evolution 2-stage
outdoor units. The 286B models use a PSC type fan motor, and the speed
does not change between high and low speed operation.
On 289B models, an ECM fan motor is used to achieve higher efficiency
ratings of the system. The outdoor unit control energizes outdoor fan
anytime compressor is operating, except for defrost or low-ambient
cooling. The outdoor fan remains energized if a pressure switch or
compressor overload should open. The outdoor fan motor will continue
to operate for one minute after the compressor shuts off when the
outdoor ambient is greater than or equal to 100°F/37.7°C. This reduces
pressure differential for easier starting on next cycle. On 286B/187B
models, the outdoor fan remains energized during the 1-minute
compressor staging time delay.
On 286B/187B models, the outdoor fan motor is a PSC type. A fan relay
on the control board turns the fan off and on by opening and closing a
high voltage circuit to the motor. It does not change speeds between low
and high stage operation.
On 289B/180B models, the outdoor fan is an ECM type. The motor
control is continuously powered with high voltage. The motor speed is
determined by electrical pulses provided by the PWM outputs on the
control board. The ECM motor RPM adjusts to outdoor conditions as
described in Table 16. The PWM output can be measured with a volt
meter set to DC volts.
In low ambient cooling (below 55°F/12.7°C), the control board cycles
the fan off and on.
Table 16 – Outdoor Fan Motor PWM

Outdoor Temp (DC volts, Tolerance +/- 2%)

Low Stage
Model
(OAT104_F / 40_C)
289B0
24 8.72
289B0
36 9.06
289B0
48 9.91
289B0
60 10.83
180B024 9.57
180B036 9.06
180B048 9.91
180B060 10.83
NOTE: For 286B models in low-ambient cooling, the PWM output for both high- and
low-stage equals the value for low-stage operation below 55_F (12.8_C).
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
High Stage Low & High Stage
(OAT104_F / 40_C) (OAT104_F / 40_C)
9.35 11.90
10.23 11.90
11.04 11.90
11.70 11.90
10.88 11.90
10.23 11.90
11.04 11.90
11.70 11.90
ECM Fan Motor Troubleshooting
If the outdoor fan motor fails to start and run:
• Check the high-voltage supply. The unit need not be running to
check high voltage, but the power must be on.
• If the 230vac is present, use
voltage output to the fan motor from the control board. The control
board sends DC voltage signals to the motor through the terminals
labeled PWM1 and PWM2 Set a voltmeter on a DC voltage scale
and check across these terminals.
• First check voltage with the motor disconnected. If no control
voltage is present, check control-board connections. If connections
are good, replace the control board.
• If voltage is present, reconnect the motor and check again. Shut
down the unit to reconnect the motor and restart the unit to
complete this troubleshooting procedure. If control voltage is no
longer present or motor fails to respond, check motor connections.
• If connections are good, replace the motor.
• The motor should run at full rpm with a 24 VAC power supplied to
the low voltage PWM signal wires. Disconnect the PWM wires
from the control board before supplying the 24 VAC to the motor.

Time Delays

The unit time delays include:
• Five minute time delay to start cooling or heating operation when
there is a call from the thermostat or user interface. To bypass this
feature, momentarily short and release Forced Defrost pins.
• Five minute compressor re-cycle delay on return from a brown-out
condition.
• Two minute time delay to return to standby operation from last
valid communication (with Evolution only).
• One minute time delay of outdoor fan at termination of cooling
mode when outdoor ambient is greater than or equal to 100_F.
• Fifteen second delay at termination of defrost before the auxiliary
heat (W1) is de-energized.
• Twenty second delay at termination of defrost before the outdoor
fan is energized.
• Thirty second compressor delay when quiet shift enabled.
• Seventy and sixty second compressor delays when Quiet Shift-2 is
enabled.
• On 25HCB6, 25HPA6, 286B, CH17 models there is a 1 minute time
delay between staging from low to high and from high to low
capacity. On 289B models there is no delay; the compressor will
change from low to high and from high to low capacity "on the fly"
to meet the demand.
56
Table 16 to check for proper control