508296-G01 / 31-5000753
Page 19 of 24
Issue 2231
Unit Operation
NS23AMA Unit Operation with a Conventional
24VAC 2-Stage Thermostat
When the NS23AMA unit is installed with a conventional
24VAC 2-stage thermostat, a Y1 first stage cooling
demand will initiate cooling operation and first stage indoor
blower operation. The compressor will be controlled in
the variable capacity mode by varying the compressor
capacity to obtain the target suction pressure set point. The
Y2 second stage cooling demand will initiate second stage
blower operation. Increased air volume will increase the
load on the indoor coil and increase the suction pressure.
The NS23AMA compressor capacity will continue to be
controlled based upon the suction pressure. The unit
capacity will be controlled in the variable capacity mode
throughout the range of capacity from minimum capacity
to maximum capacity. If the Y2 demand remains after 20
minutes, the NS23AMA control will begin to ramp up the
compressor capacity until maximum capacity is achieved.
The NS23AMA
unit will cycle off once the thermostat
demand is satisfied.
NS23AMA Unit Operation with a Conventional
24VAC Single-Stage Thermostat
When the NS23AMA unit is installed with a conventional
24VAC single-stage thermostat, a Y1 first stage cooling
demand will initiate cooling operation and cooling indoor
blower operation. In single stage thermostat applications,
a jumper must be installed between Y1 and Y2 on the
NS23AMA outdoor control. The compressor will be
controlled in the variable capacity mode by varying the
compressor capacity to obtain the target suction pressure
set point. If the cooling demand remains after 20 minutes,
the NS23AMA control will begin to ramp up the compressor
capacity until maximum capacity is achieved. The
NS23AMA
unit will cycle off once the thermostat demand
is satisfied.
Start-Up
If unit is equipped with a crankcase heater, it should
be energized 24 hours before unit start-up to prevent
compressor damage as a result of slugging.
CAUTION
1. Rotate fan to check for frozen bearings or binding.
2.
Inspect all factory and field-installed wiring for loose
connections.
3. After evacuation is complete, open liquid line and
suction line service valves to release refrigerant
charge (contained in outdoor unit) into system.
4.
Replace the stem caps and secure finger tight, then
tighten an additional 1/6 of a turn.
5. Check voltage supply at the disconnect switch. The
voltage must be within the range listed on the unit
nameplate. If not, do not start equipment until the
power company has been consulted and the voltage
condition corrected.
6. Connect manifold gauge set for testing and charging.
7. Set the thermostat for a cooling demand. Turn on
power to the indoor indoor unit and close the outdoor
unit disconnect switch to start the unit.
8. Recheck voltage while the unit is running. Power must
be within range shown on the unit nameplate.
9.
Check system for sufficient refrigerant using the
procedures outlined under Checking Refrigerant
Charge.
Operating Manifold Gauge Set and Service
Valves
The liquid and vapor line service valves are used for
removing refrigerant, flushing, leak testing, evacuating,
checking charge and charging. Each valve is equipped
with a service port which has a factory-installed valve
stem. Figure 13 and Figure 14 provide information on how
to access and operate both ball- and angle-type service
valves.
Torque Requirements
When servicing or repairing ventilating and air conditioning
components, ensure the fasteners are appropriately
tightened. Table 8 lists torque values for fasteners.
