Bryant 580D User Manual download pdf (Page 63)

CONTROLS

OPERATING SEQUENCE

Cooling, Units Without Economizer — When thermostat calls

for cooling, terminals G and Y1 are energized. The indoor

(evaporator) fan contactor (IFC) and compressor contactor

no. 1 (C1) are energized, and evaporator-fan motor (IFM), com-

pressor no. 1 (580D036-150 and 579F216-300) or unloaded

compressor (579F180), and condenser fan(s) start. The liquid

line solenoid value for compressor no. 1 is deenergized open.

The condenser-fan motor(s) runs continuously while unit is cool-

ing. For units with 2 stages of cooling, if the thermostat calls for

a second stage of cooling by energizing Y2, compressor con-

tactor no. 2 (C2) is energized and compressor no. 2 starts

(580D090-150 and 579F216-300), or compressor no. 1 runs

fully loaded (579F180). The liquid line solenoid valve for com-

pressor no. 2 (579F180 and 240) is deenergized to open.

Heating, Units Without Economizer (580D036-150) — When

the thermostat calls for heating, terminal W1 is energized. In or-

der to prevent thermostat short-cycling, the unit is locked into

the Heating mode for at least 1 minute when W1 is energized.

The induced-draft motor (IDM) is then energized and the burner

ignition sequence begins. The indoor (evaporator) fan motor

(IFM) is energized 45 seconds after a ﬂame is ignited. On units

equipped for two stages of heat, when additional heat is

needed, W2 is energized and the high-ﬁre solenoid on the main

gas valve (MGV) is energized. When the thermostat is satisﬁed

and W1 is deenergized, the IFM stops after a 45-second time-

off delay.

Heating, Units Without Economizer (579F180-300)

NOTE: The 579F180-300 units have 2 stages of heat.

When the thermostat calls for heating, power is sent to W on the

IGC (integrated gas unit controller) board. An LED (light-

emitting diode) on the IGC board will be on during normal op-

eration. A check is made to ensure that the rollout switch and

limit switch are closed. The induced-draft motor is then ener-

gized, and when speed is proven with the hall effect sensor on

the motor, 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 an-

other 5-second attempt. If the burners still do not light, this se-

quence is repeated for 15 minutes. After the 15 minutes have

elapsed, if the burners still have not lighted, 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 and limit switches, the hall effect sensor,

as well as the ﬂame sensor. If the unit is controlled through a

room thermostat set for fan auto., 45 seconds after ignition oc-

curs, the indoor-fan motor will be energized. If for some reason

the overtemperature limit opens prior to the start of the indoor

fan blower, on the next attempt, the 45-second delay will be

shortened to 5 seconds less than the time from initiation of heat

to when the limit tripped. Gas will not be interrupted to the burn-

ers and heating will continue. Once modiﬁed, the fan on delay

will not change back to 45 seconds unless power is reset to the

control.

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, inter-

rupting 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 unit is controlled

through a room thermostat set for fan auto., the indoor-fan mo-

tor will continue to operate for an additional 45 seconds then

stop. If the overtemperature limit opens after the indoor motor is

stopped within 10 minutes of W1 becoming 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.

The IGC is located by removing the side panel and viewing the

IGC through the view port located in the control box access

panel. During normal operation, the LED is continuously on.

Cooling, Units With Durablade Economizer (580D036-150)

— When the outdoor-air temperature is above the OAT

(outdoor-air thermostat) setting and the room thermostat calls

for cooling, compressor contactor no. 1 is energized to start

compressor no. 1 and the outdoor (condenser) fan motor

(OFM). The indoor (evaporator) fan motor (IFM) is energized

and the economizer damper moves to the minimum position.

Upon a further call for cooling, compressor contactor no. 2 will

be energized, starting compressor no. 2 (090-150 only). After

the thermostat is satisﬁed, the damper moves to the fully closed

position when using an auto fan or to the minimum position

when using a continuous fan.

When the outdoor-air temperature is below the OAT setting and

the thermostat calls for cooling, the economizer dampers move

to the minimum position. If the supply-air temperature is above

57 F, the damper continues to open until it reaches the fully

open position or until the supply-air temperature drops below

52 F.

When the supply-air temperature falls to between 57 F and

52 F, the damper will remain at an intermediate open position. If

the supply-air temperature falls below 52 F, the damper will

modulate closed until it reaches the minimum position or until

the supply-air temperature is above 52 F. When the thermostat

is satisﬁed, the damper will move to the fully closed position

when using an auto fan or to the minimum position when using

a continuous fan.

If the outdoor air alone cannot satisfy the cooling requirements

of the conditioned space, economizer cooling is integrated with

mechanical cooling, providing second-stage cooling. Compres-

sor no. 1 and the condenser fan will be energized and the po-

sition of the economizer damper will be determined by the

supply-air temperature. Compressor no. 2 is locked out.

When the second stage of cooling is satisﬁed, the compressor

and OFM will be deenergized. The damper position will be de-

termined by the supply-air temperature.

After a 30-second delay, the IFM shuts off. If the thermostat

fan selector switch is in the ON position, the IFM will run

continuously.

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Bryant 580D User Manual Page 63

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