Specifications

The control module will operate economizer, run diag-
nostics to monitor alarms/alerts at all times, and respond to
CCN communications to perform any configured network
POC (product outboard control) functions such as time/
outdoor-air temperature broadcast and global occupancy broad-
cast. When the optional expansion I/O board is employed,
it will: perform a periodic scan and maintain a database of
expanded I/O points; perform Fire/Smoke control (power ex-
haust required); if in Occupied mode, perform IAQ control
and monitor the fan, filter, demand limit, and field-applied
status (with accessories).
If thermostats are used to energize the G input, the control
module will turn on the indoor fan without delay and open
the economizer dampers to minimum position. If thermo-
stats are used to deenergize the G input, the control module
will turn off the indoor fan without delay and close the econo-
mizer dampers.
When cooling, G must be energized before cooling can
operate. The control module determines if outdoor condi-
tions are suitable for economizer cooling using the standard
outdoor air thermistor. For the economizer to function for
outside air cooling: the enthalpy must be below the enthalpy
set point; the outdoor-air temperature must be equal to
or less than the High Outdoor Air Temperature Lockout
(default is 65 F); the SAT (supply-air temperature) ther-
mistor must not be in alarm; and the outdoor air reading is
available. When these conditions are satisfied, the control
module will use economizer as the first stage of cooling.
When Y1 input is energized, the economizer will be modu-
lated to maintain SAT at the defined set point. (The default
is 55 F.) When SAT is above the set point, the economizer
will be 100% open. When SAT is below the set point, the
economizer will modulate between minimum and 100% open
position. When Y2 is energized, the control module will turn
on compressor 1 and continue to modulate the economizer
as described above. If the Y2 remains energized and the SAT
reading remains above the set point for 15 minutes, com-
pressor 2 will turn on. If Y2 is deenergized at any time, only
the last stage of compression that was energized will be turned
off. If outdoor conditions are not suitable for economizer cool-
ing, the economizer will go to minimum position and cycle
compressors 1 and 2 based on demand from Y1 and Y2
respectively. The compressors will be locked out when the
SAT temperature is too low (less than 40 F for compressor
1 and less than 45 F for compressor 2). After a compressor
is locked out, it can restart after normal Time Guardt
period.
The Time Guard function maintains a minimum off time
of 5 minutes, a minimum on time of 10 seconds, and a
minimum delay before starting the second compressor of
10 seconds.
Heating — The control module is powered by 24 vac. If
the unit is controlled with a room sensor, the fan will run
continuously in the Occupied mode, with the outside-air damper
in the minimum position. If the unit is controlled through a
room thermostat (with FAN set to AUTO), upon a call for
heat the first stage heat is energized, energizing heat relay
(HR2) and reversing valve solenoids (RVS1 and 2). Com-
pressor no. 1 and 2, indoor and outdoor-fan motors start. Upon
a call for additional heat (if equipped with electric heaters),
the second stage of heat is energized. When the call for heat
is satisfied, the compressors, fan motors, and heaters will be
deenergized and the outdoor-air damper will move to the closed
position.
If the unit is controlled with a room sensor the fan will not
run in the Unoccupied mode unless the space temperature is
below the unoccupied heat set point or above the unoccu-
pied cool set point. Upon a call for heat, the first stage of
heat is energized, energizing heat relay (HR2) and revers-
ing valve solenoids (RVS1 and 2). Compressor no. 1 and 2,
indoor and outdoor-fan motors start, and the outdoor-air damper
will move to the Unoccupied IAQ position (generally set to
zero in the Unoccupied mode). The IAQ feature is enabled
through system software. Upon a call for additional heat (if
equipped with electric heaters), the second stage of heat is
energized. When the call for heat is satisfied, the compres-
sors, fan motors, and heaters will be deenergized and the
outdoor-air damper will move to the closed position.
Defrost Cycle — When the temperature of the outdoor
coil drops below 28 F as sensed by the defrost thermostat
(DFT1 or 2) and the defrost timer is at the end of a timed
period (adjustable at 30 to 90 minutes) the defrost cycle will
begin. The control board will deenergize the reversing valve
solenoids (RVS1 and 2) and energize the electric heat. Also,
the outdoor-fan motor will stop.
The unit will continue to defrost until the coil temperature
as measured by DFT1 and 2 reaches 65 F or the duration of
defrost cycle completes a 10-minute period.
During the defrost mode, if a circuit defrosts first, the RVS
will oscillate between heating and cooling modes until de-
frost mode is complete. This will keep the head pressure on
that circuit from getting too high.
At the end of the defrost cycle, the electric heaters will be
deenergized, reversing valve solenoids will be energized, and
the outdoor fan will start.
POWER EXHAUST OPERATION
Power exhaust has two options (Constant Volume and Modu-
lating) that have the following sequence of operation:
The first stage of constant volume (CV) power exhaust is
enabled when the indoor fan has been energized and the
desired damper position for the economizer increases above
the CV power exhaust set point (PES1). The default for PES1
is set at 25%. The second stage of power exhaust is enabled
when the desired damper position for the economizer
increases above the second CV power exhaust set point (PES2).
The default for PES2 is set at 75%. Each stage is disabled
when the desired damper position decreases below the
respective set points.
The modulating power exhaust is enabled when the in-
door fan is energized and the building pressure has exceeded
the individual sequencer set points. The default set points
are 0.04 in. wg (9.9 Pa) (6.3 vdc) for stage 1, 0.10 in. wg
(24.9 Pa) (6.8 vdc) for stage 2, 0.16 in. wg (39.8 Pa)
(7.3 vdc) for stage 3, 0.23 in. wg (57.1 Pa) (7.8 vdc) for
stage 4, 0.29 in. wg (72.0 Pa) (8.3 vdc) for stage 5, and
0.35 in. wg (86.9 Pa) (8.8 vdc) for stage 6 power exhaust
sequencer. Each stage also requires that the building pres-
sure is reduced until it drops below the disable set point. The
default set points are 0 in. wg (0 Pa) (6.0 vdc) for stage 1,
0.060 in. wg (14.9 Pa) (6.5 vdc) for stage 2, 0.13 in. wg
(32.3 Pa) (7.0 vdc) for stage 3, 0.19 in. wg (47.2 Pa)
(7.4 vdc) for stage 4, 0.25 in. wg (47.5 Pa) (8.0 vdc) for
stage 5, and 0.31 in. wg (62.4 Pa) (8.5 vdc) for stage 6 power
exhaust sequencer. Both of these set points are changed at
the specific controlling sequencer.
SMOKE CONTROL MODES
The 48/50EJ,EK,EW,EY and 50EJQ,EWQ units with an
optional expansion board perform fire and smoke control modes.
The expansion board provides 4 modes which can be used
to control smoke within the conditioned area. The modes of
operation are fire shutdown, pressurization, evacuation, and
smoke purge. See Table 3.
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