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508133G01 / 31-5000715
Issue 2140
4. The unit will display the unit type for 10 seconds. Press
the push button and hold it for 3 seconds for the unit
to store the unit type. Once, the unit code is stored
the system acknowledges by displaying a string of
characters ending with the updated system unit code.
After programming of unit type is complete, the unit can be
set up for charge mode operation.
Charge Mode Jumper
To initiate the NS18HMA Charge Mode function, install
the jumper across the two Charge Mode Pins (CHRG
MODE) on the outdoor control. The Charge Mode can be
used when charging the system with refrigerant, checking
the refrigerant charge, pumping down the system and
performing other service procedures that requires outdoor
unit operation at 100% capacity.
NS18HMA
Charge Mode Operation with a Conventional
24VAC Heat Pump Thermostat
Charge Mode Display String
When unit is in the charge mode, Suction Pressure
(SPxxx), Suction Temp (Stxx.x), Superheat (SHxx.x), Liquid
Pressure (LPxxx), Liquid Temp (Ltxx.x) and Subcooling
(SCxx.x) will be scrolled on the 7-segment display.
Example:
S P 1 3 5
pause
S t 6 2
pause
S H 1 5
pause
L P 3 4 5
pause
L t 9 6
pause
S C 1 0
repeat
Charge Mode Jumper Operation in the Cooling Mode
On applications with a conventional 24VAC heat pump
thermostat, the charge mode jumper must be installed on
the Charge Mode Pins after providing a cooling compressor
demand to the NS18HMA and an “O” cooling reversing
valve demand to initiate the Charge Mode. A cooling
blower demand must also be provided to initiate blower in
high stage operation on the indoor unit.
The compressor and outdoor fan motor will begin to ramp
up and reach 100% design capacity within 3 minutes. They
will continue to operate at 100% design capacity for the
duration of charge mode.
Charge Mode Jumper Operation in the Heat Pump
Heating Mode
On applications with a conventional 24VAC heat pump
thermostat, the charge mode jumper must be installed
on the Charge Mode Pins after providing a heating
compressor demand to the NS18HMA without an “O”
reversing valve signal to initiate the Charge Mode. A
heating blower demand must also be provided to initiate
high speed blower operation on the indoor unit.
The compressor and outdoor fan motor will begin to ramp
up and reach 100% design capacity within 3 minutes. They
will continue to operate at 100% design capacity for the
duration of charge mode.
Exiting Charge Mode
To exit the charging mode, remove the Charge Mode
Jumper from the Charge Mode Pins. The system will
be in Charge Mode for a maximum time of 60 minutes
and will automatically exit the charge mode and resume
normal operation after 60 minutes even if the charge mode
jumper is left in place. To extend the charge mode beyond
60 minutes, ensure the cooling/heating demand, blower
demand and appropriate reversing valve demand are
available and reapply the charge mode jumper.
NOTE:
If compressor demand is lost during charge mode
period, then the compressor and fan will cease to operate,
and the unit will enter into a delay timer for 3 minutes.
Repeat the charging mode procedure to get back into
charge mode.
Cooling Operation Mode Jumper
The Cooling Operation Mode Jumper is only used on
applications installed with a conventional 24VAC heat
pump thermostat. In applications with a conventional
24VAC heat pump thermostat, the compressor capacity is
controlled to maintain the target suction pressure setpoint.
The Cooling Operation Mode Jumper has three selectable
cooling modes. The three modes are Efficiency (Jumper
installed on Pins 1 & 2), Normal Mode (Jumper installed
on Pins 2 & 3) and Comfort Mode (Jumper Removed).
The factory default position is the Efficiency Mode. The
Efficiency mode has a variable suction pressure setpoint
that will vary with the outdoor temperature; as the outdoor
temperature increases the suction pressure setpoint will
decrease. When the Cooling Operation Mode jumper
is installed in the “Normal Mode” the suction pressure
setpoint is 135 psig.
When the Cooling Operation Mode jumper is installed in
the “Comfort Mode” the suction pressure setpoint is 125
psig.
Operation Mode
Jumper
Jumper
Position
Target Suction
Pressure Setting
Efficiency (default)
Pin 1 to Pin 2
Variable based on OAT
Normal
Pin 2 to Pin 3
135 PSIG
Comfort
Jumper Off
125 PSIG
Table 9. Cooling Operation Mode Jumper
(Conventional 24VAC Thermostats Only)
