Sequence Of Operation - Bryant 581J Series Manual

SEQUENCE OF OPERATION

General
— The sequence below describes the sequence of op-
eration for an electro-mechanical unit with and without a facto-
ry-installed EconoMi$er ®
this sequence). For information regarding a direct digital con-
troller, see the start-up, operations, and troubleshooting manual
for the applicable controller.
Electro-Mechanical Units with No Economizer Cool-
ing (Single Speed Indoor Fan Motor)
mostat calls for cooling, terminals G and Y1 are energized. As
a result, the indoor-fan contactor (IFC) and the compressor
contactor (C1) are energized, causing the indoor-fan motor
(IFM), compressor #1, and outdoor fan to start. If the unit has 2
stages of cooling, the thermostat will additionally energize Y2.
The Y2 signal will energize compressor contactor #2 (C2),
causing compressor #2 to start. Regardless of the number of
stages, the outdoor-fan motor runs continuously while unit is
cooling.
Cooling (2-speed indoor fan motor) —
90.1-2016 standards during the first stage of cooling operation
the VFD will adjust the fan motor to provide 66% of the total
cfm established for the unit. When a call for the second stage of
cooling is required, the VFD will allow the total cfm estab-
lished for the unit (100%).
Heating
NOTE: Preferred Series (581J) units have 2 stages of gas heat.
When the thermostat calls for heating, power is sent to W on
the Integrated Gas Controller (IGC) board. An LED (light-
emitting diode) on the IGC board turns on and remains on
during normal operation. A check is made to ensure that the
rollout switch and limit switch are closed. If the check was suc-
cessful, the induced-draft motor is energized, and when its
speed is satisfactory, as proven by the "hall effect" sensor, the
ignition activation period begins. The burners will ignite within
5 seconds. If the burners do not light, there is a 22-second delay
before another 5-second attempt. This sequence is repeated for
15 minutes or until the burners light. If, after the 15 minutes,
the burners still have not lit, heating is locked out. To reset the
control, break 24-v power to the thermostat.
When ignition occurs, the IGC board will continue to monitor
the condition of the rollout switch, the limit switches, the "hall
effect" sensor, as well as the flame sensor. Forty-five seconds
after ignition occurs, assuming the unit is controlled through a
room thermostat set for fan auto, the indoor-fan motor will en-
ergize (and the outdoor-air dampers will open to their minimum
position). If, for some reason, the over-temperature limit opens
prior to the start of the indoor fan blower, the unit will shorten
the 45-second delay to 5 seconds less than the time from initia-
tion of heat to when the limit tripped.
Gas will not be interrupted to the burners and heating will con-
tinue. Once the fan-on delay has been modified, it will not
change back to 45 seconds until power is reset to the control.
On units with 2 stages of heat, when additional heat is required,
W2 closes and initiates power to the second stage of the main
gas valve. When the thermostat is satisfied, W1 and W2 open
and the gas valve closes, interrupting the flow of gas to the
main burners.
If the call for W1 lasted less than 1 minute, the heating cycle
will not terminate until 1 minute after W1 became active. If the
IV and X (called "economizer" in
— When the ther-
Per ASHRAE
unit is controlled through a room thermostat set for fan auto,
the indoor-fan motor will continue to operate for an additional
45 seconds then stop. If the over-temperature limit opens after
the indoor motor is stopped, but within 10 minutes of W1 be-
coming inactive, on the next cycle the time will be extended by
15 seconds. The maximum delay is 3 minutes. Once modified,
the fan off delay will not change back to 45 seconds unless
power is reset to the control. A LED indicator is provided on
the IGC to monitor operation.
Electro-Mechanical Units with Factory-Installed
EconoMi$er Cooling (Single Speed Indoor Fan
Motor)
Cooling —
When free cooling is not available, the compressors
will be controlled by the zone thermostat. When free cooling is
available, the outdoor-air damper is modulated by the
EconoMi$er IV and X control to provide a 50°F (10°C) to 55°F
(13°C) mixed-air temperature into the zone. As the mixed air tem-
perature fluctuates above 55°F (13°C) or below 50°F (10°C)
dampers will be modulated (open or close) to bring the mixed-air
temperature back within control. If mechanical cooling is utilized
with free cooling, the outdoor-air damper will maintain its current
position at the time the compressor is started. If the increase in
cooling capacity causes the mixed-air temperature to drop below
45°F (7°C), then the outdoor-air damper position will be decreased
to the minimum position. If the mixed-air temperature continues to
fall, the outdoor-air damper will close. Control returns to normal
once the mixed-air temperature rises above 48°F (9°C). The power
exhaust fans will be energized and de-energized, if installed, as the
outdoor-air damper opens and closes
If field-installed accessory CO
EconoMi$er IV and X control, a demand controlled ventilation
strategy will begin to operate. As the CO
es above the CO set-point, the minimum position of the damper
2
will be increased proportionally. As the CO
cause of the increase in fresh air, the outdoor-air damper will be
proportionally closed. For EconoMi$er IV and X operation, there
must be a thermostat call for the fan (G). If the unit is occupied and
the fan is on, the damper will operate at minimum position. Other-
wise, the damper will be closed.
When the EconoMi$er IV and X control is in the occupied mode
and a call for cooling exists (Y1 on the thermostat), the control will
first check for indoor fan operation. If the fan is not on, then cool-
ing will not be activated. If the fan is on, then the control will open
the EconoMi$er IV and X damper to the minimum position.
On the initial power to the EconoMi$er IV and X control, it will
take the damper up to 2 / minutes before it begins to position it-
1
2
self. After the initial power-up, further changes in damper position
can take up to 30 seconds to initiate. Damper movement from full
closed to full open (or vice versa) will take between 1
minutes. If free cooling can be used as determined from the appro-
priate changeover command (switch, dry bulb, enthalpy curve, dif-
ferential dry bulb, or differential enthalpy), then the control will
modulate the dampers open to maintain the mixed-air temperature
set-point at 50°F (10°C) to 55°F (13°C). If there is a further de-
mand for cooling (cooling second stage − Y2 is energized), then
the control will bring on compressor stage 1 to maintain the
mixed-air temperature set-point. The EconoMi$er IV and X
damper will be open at maximum position.
sensors are connected to the
2
level in the zone increas-
2
level decreases be-
2
1 / and 2
2
1 /
2
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