33
Operating Sequence —
All units require the addition
of a thermostat accessory package to complete the control cir-
cuit. The sequence of operation may vary depending on which
package is selected.
ROOM-MOUNTED THERMOSTAT — These units use an
electronic thermostat mounted in the conditioned space.
FAN CIRCULATION — The indoor-fan motor is energized
through G on the thermostat and the indoor-fan contactor is en-
ergized. This starts the indoor-fan motor (IFM). The fan will
operate to provide continuous air circulation.
COOLING — The indoor fan will operate continuously or
when the compressor runs, depending on the setting of the ther-
mostat fan selector switch. When the thermostat closes on a
call for cooling (Y1) the compressor contactor closes to start
the first stage compressor.
If additional cooling demand is required, the second stage
(Y2) on 50XCW12-24 units will close and will then start the
second-stage compressor. When the thermostat is satisfied, the
second-stage compressor will stop first, and then the first-stage
compressor will stop when cooling demand is satisfied.
HEATING (IF EQUIPPED WITH HOT WATER OR
STEAM COIL) — When thermostat closes on a call for heat-
ing (W1), it will engage beginning stages of heating.
ECONOMIZER OPERATION — Economizer operation is
enabled if entering water set point is above water supply tem-
perature and there is a call for first stage cooling (Y1 closes at
the thermostat). If the water supply temperature is above the set
point then economizer operation will be disabled and the first
stage cooling will enable compressor operation. Economizer
control valve will be modulated open or closed to maintain a
supply-air temperature between 50 and 55°F. The economizer
valve will be fully open when the supply-air temperature ex-
ceeds 55°F. On call for second stage cooling if economizer is
enabled, first-stage compressors will be enabled if entering-
water temperature is still below set point.
To adjust the changeover set point, press and hold the
MENU button until the display flashes “SP” (about 2 seconds).
Press MENU again to display the existing set point value. Use
the up or down arrows to change the set point value and then
press MENU again to save the new value.
2-SPEED FAN OPERATION SEQUENCE — On the VFD
the following parameters must be set on each unit. To change
the parameters:
1. Press MENU.
2. Select Parameters.
3. Press ENTER.
4. Select sub-group (first two digits of the parameters).
5. Press SEL.
6. Select parameter.
7. Press EDIT.
8. Select the new value. (See Table 10.)
9. Press SAVE.
10. Select any other parameters of the group to change and go
to Step 7.
11. When complete, press EXIT.
12. Select any other parameter groups to change and go to
Step 5.
13. When complete, Press EXIT.
14. Press EXIT until the status menu is visible (HZ, PSI,
PSI).
Table 10 — VFD Parameters
On the VFD, the following parameters must be loaded from
the IFM-VFD configuration keypad. The parameter list is pro-
vided should the keypad be damaged and the points loaded
manually. (See Table 11.) To download parameters from the
configuration keypad:
1. Press MENU.
2. Select PAR Backup.
3. Press SEL.
4. Select Download to Drive ALL.
5. Press SEL.
6. When download is complete press SEL.
Table 11 — IFM - VFD Parameters
Should it be necessary to upload data to the configuration
keypad:
1. Press MENU.
2. Select PAR Backup.
3. Press SEL.
4. Select Upload to Panel.
5. Press SEL.
6. When download is complete press SEL.
ALL UNITS — The control circuit incorporates a current
sensing lockout relay (Cycle-LOC™ device) that locks off the
compressor(s) for 5 minutes when any safety device is activat-
ed (low or high pressure switches, or compressor internal over-
load). If any compressor safety device opens, the compressor
will stop. High and low-pressure switches and compressor mo-
tor overload protectors will reset automatically when the condi-
tion which caused the device to trip has dropped below the re-
set condition. To reset the Cycle-LOC control device, manually
turn the control power OFF, then back ON.
Water Regulating Valve —
The water regulating
valve is a direct acting 2-way pressure actuating water regulat-
ing valve located on the inlet of the condenser that modulates
water flow to control discharge pressure of the compressors
above a minimum head pressure. This valve allows the unit to
operate with entering water temperatures as low as 40°F.
PARAMETER
INDEX
PARAMETER
FUNCTION
CHANGES FROM STANDARD
MACRO
9906
Motor Nominal Voltage
Set to Unit Voltage (208/230V =
230V, 460V, or 575V)
9907
Motor Nominal Current
Motor FLA
9908
Motor Nominal Speed
Motor Nameplate
9909
Motor Nominal Power
Motor HP
PARAMETER
INDEX
PARAMETER
FUNCTION
CHANGES FROM STANDARD
MACRO
9902
Application Macro
1 (HVAC Default)
1101
Keypad Ref Sel
2 - REF2 (%)
1102
EXT 1 - EXT 2 SEL
7 - EXT 2
1106
REF2 Select
2 - AI2
1107
REF2 Minimum
67%
1201
Constant Speed Select
-2 - DI2(INV)
1202
Const Speed 1
60 Hz
1601
Run Enable
1 - DI1
1608
Start Enable
0 - Not Sel
1611
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