Step 13 Start−Up; Step 14 − System Functions And Sequence Of Operation - Carrier 25HNA Infinity
Series Installation Instructions Manual

Step 13 Start−Up
CAUTION
!
UNIT OPERATION AND SAFETY HAZARD
Failure to follow this caution may result in minor personal
injury, equipment damage or improper operation.
Observe the following:
S Do not overcharge system with refrigerant.
S Do not operate unit in a vacuum or at negative pressure.
S Do not disable low pressure switch
S Dome temperatures may be hot.
CAUTION
!
PERSONAL INJURY HAZARD
Failure to follow this caution may result in personal injury.
Wear safety glasses, protective clothing, and gloves when
handling refrigerant.
CAUTION
!
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
temperature. 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
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 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
appropriate time delay(s). Operate unit for 15 minutes.
Check refrigerant charge.
Step 14 System Functions and Sequence of Operation
The outdoor unit control system has special functions. The
following is an overview of the two−stage control functions:
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. 9)
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.
Amber Status Light
An amber colored STATUS light is used to display the operation
mode and fault codes as specified in the troubleshooting section.
See Table 7 for codes and definitions.
NOTE: Only one code will be displayed on the outdoor unit
control board (the most recent, with the highest priority).
Utility Interface
With Infinity Control
The utility curtailment relay should be wired between R and Y2
connections on the control board for Infinity Communicating
Systems only (see Fig. 9.) This input allows a power utility
device to interrupt compressor operation during peak load
periods. When the utility sends a signal to shut the system down,
the User Interface will display, "Curtailment Active".
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