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General

— The sequence below describes the sequence of op-

eration for an electro-mechanical unit with and without a facto-
ry-installed EconoMi$er

IV and X (called “economizer” in

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)

—

When the ther-

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) —

Per ASHRAE

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

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

sensors are connected to the

EconoMi$er IV and X control, a demand controlled ventilation
strategy will begin to operate. As the CO

level in the zone increas-

es above the CO

set-point, the minimum position of the damper

will be increased proportionally. As the CO

level decreases be-

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-

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

and 2

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

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