33
FAN CIRCULATION
The indoor-fan motor is energized through G on the thermostat
and the indoor-fan contactor is energized. 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 thermostat fan selector
switch. When the thermostat closes on a call for cooling (Y1), the
outdoor fan relay (OFR) or outdoor-fan contactor (OFC) are ener-
gized to start the condenser fan and compressor contactor closes to
start the first stage compressor.
If additional cooling demand is required, the second stage (Y2)
will close and will then start the second stage of compression.
When the thermostat is satisfied, the second stage compressor will
stop first, and then the first stage compressors will stop when cool-
ing demand is satisfied. The outdoor fan will also stop as soon as
the first stage cooling is satisfied.
HEATING
The indoor fan will operate continuously or when the heater runs,
depending on the setting of the thermostat fan selector switch.
When the thermostat closes (on a call for heating), the thermostat
activates the water or steam control valve (provided by customer)
or electric heater to meet heating requirements.
ALL UNITS
The control circuit incorporates a current sensing lockout relay
(Cycle-LOC™ device) that locks off the compressor(s) for 5 min-
utes when any safety device is activated (low or high-pressure
switches, or compressor internal overload). If any compressor
safety device opens, the compressor will stop. High and low-pres-
sure switches and compressor motor overload protectors will reset
automatically when the condition which caused the device to trip
has dropped below the reset condition. To reset the Cycle-LOC
control device, manually turn the control power OFF, then back
ON at the thermostat.
Low Ambient Operation (Factory Installed)
Refrigerant pressure controlled VFD (variable frequency drive)
adjusts fan speed to control head pressure. This fan speed control
permits unit to operate in cooling even in winter, when outdoor air
temperature is down to 0°F. Dual circuit units have transducers
that monitor refrigerant pressure on each circuit and provide
continuous operation in the event one circuit is down. The
VFD is pre-programmed and run tested at factory set point for
discharge pressure of 400 psig.
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 16).
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).
Table 16 — VFD Parameters
On the VFD, the following parameters must be loaded from the
IFM-VFD configuration keypad. The parameter list is provided
should the keypad be damaged and the points loaded manually
(see Table 17). 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 17 — 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.
When download is complete, press SEL.
Configuration of Low Ambient Kit
(Field Installation)
The original unit should have the wiring diagrams as shown in the
typical wiring schematic in Troubleshooting section. The motor
start and wiring should be replaced with a 24-v relay and the VFD,
with the wiring shown in either the typical wiring schematic for
low ambient option (50XCA06-24 units). Wiring diagrams are
provided in Troubleshooting section.
Be sure the VFD jumper wires are set as shown in the wiring dia-
gram and the two DIP switches are set to the “0” position for volt-
age control.
The parameters shown in Table 18 must be set for low ambient op-
eration. Motor FLA (full load amps) values are shown in Table 19
(208/230-v and 460-v) and Table 20 (575-v) for reference. Use ac-
tual nameplate motor FLA value since this value is subject to
change.
When the drive is installed and wired, it will be necessary to con-
figure the drive for this application, as follows:
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 - AL2
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 View Long View
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