Start-Up; Cooling And Heating Operation; Communication And Status Function Lights; System Functions And Sequence Of Operation - Carrier 25HNA6 Installation Instruction

For o ther combinations ofequipment consult Product Data D igest.
Start-Up
UNIT OPERATION AND SAFETY HAZARD
Failure to follow this caution may result in minor personal
injury, equipment damage or improper operation.
Observe the following:
1. Do not overcharge system with refrigerant.
2. Do not operate unit in a vacuum or at negative pressure.
3. Do not disable low pressure switch
4. Dome temperatures may be hot.
PERSONAL INJURY HAZARD
Failure to follow this caution may result in personal injury.
Wear safety glasses, protective clothing, and gloves when
handling refrigerant.
ENVIRONMENTAL HAZARD
Failure to follow this caution may result in environmental
damage.
Federal regulations require that you do not vent
refrigerant to the atmosphere. Recover during system
repair or final unit disposal.
Follow these steps to properly start up the system:
1. After system is evacuated, fully back seat (open) liquid and
vapor service valves.
2. Unit is shipped with valve stem(s) front seated (closed) and
caps installed. Replace stem caps after system is opened to
refrigerant flow (back seated). Replace caps finger-tight and
tighten with wrench an additional 1/12 turn.
3. Close electrical disconnects to energize system.
4. Set room thermostat or User Interface at desired temperat-
ure. Be sure set point is below indoor ambient temperature
and is set low enough to energize desired stage.
5. Set room thermostat or User Interface to COOL and fan
control to ON or AUTO mode, as desired. Operate unit for
15 minutes. Check system refrigerant charge.
NOTE: For 25HNA6 Series only using non-communicating
(non-Infinity) thermostat. Carrier electronic thermostats are
equipped with a 15-minute staging timer. This timer prevents the
two-stage system from operating at high stage until unit has been
operating in low stage for 15 minutes, unless there is at least a ---5°F
(-2.8°C) difference between room temperature and thermostat set
point. To force high stage (after a minimum of 2 minutes in low
stage), adjust the set point at least -5°F (-2.8°C) below room
ambient.
6. Set room thermostat or User Interface to HEAT or COOL
and fan control to AUTO or ON, as desired. Wait for appro-
priate time delay(s). Operate unit for 15 minutes. Check re-
frigerant charge.
System Functions and Sequence of Operation
The outdoor unit control system has special functions, The
following is an overview of the two-stage control flmctions:
Cooling and Heating Operation
The 25HNA6 model utilizes either a standard indoor thermostat or
Infinity Communication User Interface. The 25HNA9 models
utilize an Infinity communicating User Interface only. With a call
for first stage cooling, the outdoor fan, reversing valve, and low
stage compressor are energized. If low-stage cannot satisfy cooling
demand, high-stage cooling is energized by the second stage of
indoor thermostat or User Interface. After second stage is satisfied,
the unit returns to low-stage operation until first stage is satisfied
or until second stage is required again. When both first stage and
second stage cooling are satisfied, the compressor will shut off. The
reversing valve will remain energized until the control board power
is removed or a call for heating in initiated. With a call for heating,
the outdoor fan and compressor are energized. The compressor will
operate in high or low stage operation, as needed to meet the
heating demand. When the heating demand is satisfied, the
compressor and fan will shut off. The reversing valve is
de-energized in the heating mode.
NOTE: When two-stage unit is operating at low-stage, system
vapor (suction) pressure will be higher than a standard single-stage
system or high-stage operation.
NOTE: Outdoor fan motor will continue to operate for one
minute after compressor shuts off, when outdoor ambient is greater
than or equal to 100°F. This reduces pressure differential for easier
starting on next cycle.
NOTE: On 25HNA6 models, if unit has not operated within the
past 12 hours, or following a unit power-up, upon the next
thermostat high- or low-stage demand, unit operates for a
minimum of 5 minutes in high-stage.
On 25HNA6 models with non-communicating (non-Infinity)
systems, with first stage of cooling, Y1 and O are powered on; and
with second stage of cooling, Y1, Y2, and O are on. For these
systems, with first stage of heating Y1 is on and for second stage of
heating, Y1 and Y2 are on. When the reversing valve is energized,
O is powered on.
Communication and Status Function Lights
For Infinity Control only, Green communications (COMM)
Light
A green LED (COMM light) on the outdoor board (see Fig. 6)
indicates successful communication with the other system
products. The green LED will remain OFF until communication is
established. Once a valid command is received, the green LED will
turn ON continuously. If no communication is received within 2
minutes, the LED will be turned OFF until the next valid
communication.