Carrier 50EJQ Installation, Start-Up And Service Instructions Manual page 23

Crankcase Heater(s) —
as there is power to the unit, except when the compressors
are operating.
IMPORTANT: Unit power must be on for 24 hours
prior to start-up. Otherwise, damage to compressor may
result.
Indoor Fan —
Fan belt and fixed pulleys are factory-
installed. See Tables 11 and 12 for Fan Performance Data.
See Table 13 for Motor Limitation data. Be sure that fans
rotate in the proper direction. Static pressure drop for power
exhaust, barometric relief damper, and electric heat is neg-
ligible. To alter fan performance, see Indoor Fan Perfor-
mance Adjustment section on page 29.
Outdoor Fans and Motors —
are factory set. Refer to Outdoor-Fan Adjustment section
(page 30) as required.
Return-Air Filters —
installed in filter tracks. See Table 1. Do not operate unit
without return-air filters.
Filter Replacement —
access door (marked with label). Remove inner access panel.
Remove plastic filter retainer in between filter tracks by slid-
ing and pulling outward. Remove first filter by sliding it out
of the opening in filter track. Locate filter removal tool, which
is shipped next to the return air dampers. Use the filter
removal tool to remove the remaining filters.
Outdoor-Air Inlet Screens —
must be in place before operating unit.
Economizer Adjustment —
Check that outdoor-air damper is closed and return-air damper
is open.
Economizer operation and adjustment is described in
Sequence of Operation and Make Outdoor Air Inlet Adjust-
ments sections (this page and page 14), respectively.
Sequence of Operation
NOTE: Unit is shipped with default values that can be changed
through Service Tool or CCN software.
COOLING — On power up, the control module will acti-
vate the initialization software. The initialization software
reads DIP switch no. 1 position to determine CV operation.
Next, DIP switch no. 2 is read to determine if the control is
thermostat or sensor type operation. The initialization
sequence: clears all alarms and alerts; re-maps the input/
output database for CV operation; sets maximum heat stages
to 2; and sets maximum cool stages to 3. The control module
reads DIP switch no. 3 and determines if the unit will use
expansion mode operation.
The thermostat function performs a thermostat based con-
trol by monitoring Y1, Y2, W1, W2 and G inputs. These
functions control stages: cool1, cool2, heat1, heat2, and the
indoor fan respectively. If the TSTAT function is not
selected, the control module determines the occupancy state
based on the system time schedules or with remote occupied/
unoccupied input. If Temperature Compensated Start is
active, the unit will be controlled as in the Occupied mode.
User defined set points are shown in Table 14.
Occupied or unoccupied comfort set points must be
selected. Use of the space temperature offset input can also
Heater(s) is energized as long
Fans and motors
Check that correct filters are
To replace filters, open filter
Outdoor-air inlet screens
Remove filter access panel.
be configured. The control module will set appropriate
operating mode and fan control. The control module will turn
on indoor fan if in Occupied mode or if the unit is in Un-
occupied mode and the space temperature is outside of the
unoccupied comfort set points (Unoccupied Heat or Un-
occupied Cool). The control module will then monitor space
temperature against comfort set points and control heating
or cooling stages as required. If the system is in the Occu-
pied mode, the economizer will operate as required. If the
system is in Unoccupied mode, the system will perform night-
time free cool and IAQ (indoor air quality) pre-occupancy
purge as required (when functions are enabled via software).
Whenever the DX (direct expansion) cooling is requested,
the outdoor fan will operate.
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
exhaust required); if in Occupied mode, perform IAQ con-
trol 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 (de-
fault is 65 F); the SAT (supply-air temperature) thermistor
must not be in alarm; and the outdoor air reading is avail-
able. When these conditions are satisfied, the control mod-
ule 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 re-
spectively. 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-guard 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.
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