20
QUIET SHIFT
Quiet Shift is a field--selectable defrost mode which may eliminate
occasional noise that could be heard at the start of the defrost cycle
and restarting of the heating cycle. This feature must be enabled at
the UI. When activated, the following sequence of operation will
occur. Reversing valve will energize and compressor will turn off
for 30 seconds, then turn back on to complete defrost. At the end
of the defrost cycle, the reversing valve de--energizes, compressor
will turn off for another 30 seconds, and the fan will turn off for 40
seconds, before starting in the heating mode.
Step 3 — Check for Refrigerant Leaks
Locate and repair refrigerant leaks and charge the unit as follows:
1. Use both high-- and low--pressure ports to relieve system
pressure and reclaim remaining refrigerant.
2. Repair leak following accepted practices.
NOTE
: Install a filter drier whenever the system has been opened
for repair.
3. Check system for leaks using an approved method.
4. Evacuate refrigerant system and reclaim refrigerant if no
additional leaks are found.
5. Charge unit with Puron (R--410A) refrigerant, using an
accurate scale. Refer to unit rating plate for required charge.
Step 4 — Start--Up Adjustments
Complete the required procedures given in the Pre--Start--Up
section before starting the unit. Do not jumper any safety devices
when operating the unit. Do not operate the unit in cooling mode
when the outdoor temperature is below 40
°
F (4
_
C) (unless
low--ambient operation is enabled in the UI). Do not rapid cycle
the compressor. Allow 5 min. between “on” cycles to prevent
compressor damage.
CHECKING
COOLING
AND
HEATING
CONTROL
OPERATION
See UI Installation Instructions for detailed system CHECKOUT.
CHECKING AND ADJUSTING REFRIGERANT CHARGE
The refrigerant system is fully charged with Puron (R--410A)
refrigerant and is tested and factory sealed.
NOTE
: Any adjustment to refrigerant charge must be done with
unit operating in HIGH stage.
NOTE
:
Adjustment of the refrigerant charge is not required
unless the unit is suspected of not having the proper R--410A
charge. The charging label and the tables shown refer to system
temperatures and pressures in cooling mode only. A refrigerant
charging label is attached to the outside of the unit. If charge level
is suspect in heating mode, reclaim all refrigerant and charge to
rating plate amount. (This information may be obtained from the
physical data table also.)
IMPORTANT
:
When evaluating the refrigerant charge, an
indicated adjustment to the specified factory charge must always be
very minimal. If a substantial adjustment is indicated, an abnormal
condition exists somewhere in the cooling system, such as
insufficient airflow across either coil or both coils.
REFRIGERANT CHARGE
The amount of refrigerant charge is listed on the unit rating plate
and/or the physical data table. Refer to the Refrigeration Service
Techniques Manual, Refrigerants Section.
NO CHARGE
Check for leak. Use standard evacuating techniques. After
evacuating system, weigh in the specified amount of refrigerant
(refer to system rating plate).
LOW CHARGE COOLING
Use Cooling Charging Chart (Fig. 19). Vary refrigerant until the
conditions of the chart are met. Note that charging charts are
different from type normally used. Charts are based on charging
the units to correct subcooling for the various operating conditions.
Accurate pressure gauge and temperature sensing devices are
required. Connect the pressure gauge to the service port on the
suction line. Mount the temperature sensing device on the suction
line and insulate it so that the outdoor ambient does not affect the
reading. Indoor air CFM must be within the normal operating
range of the unit.
TO USE COOLING CHARGING CHARTS
Take the liquid line temperature and read the manifold pressure
gauges.
Refer to the chart to determine what the liquid line temperature
should be.
NOTE
:
If the problem causing the inaccurate readings is a
refrigerant leak, refer to Check for Refrigerant Leaks section.
INDOOR AIRFLOW AND AIRFLOW ADJUSTMENTS
NOTE
: Be sure that all supply-- and return--air grilles are open,
free from obstructions, and adjusted properly.
The 50XT--A unit utilizes state of the art ECM (Electronic
Computated Motor) ID Blower Motors. See UI instructions for
detailed information on adjusting airflow.
NON--COMMUNICATING
EMERGENCY
COOLING
/
HEATING MODE
This mode of operation is provided only in the case where the UI
has failed or is otherwise unavailable. If communications cannot be
established with the UI, the Infinity fan coil board will enable the
R, C, Y, O, and W input terminals to allow simple thermostatic
control of the 50XT--A unit.
For control with a standard thermostat, disconnect the ABCD
connectors from both control boards and using No. 18 AWG
color--coded, insulated type 90
°
C minimum or equivalent wire,
make the connections between the standard thermostat, the fan coil
board, and the HP/AC board per Fig. 18. Recommend the use of
interconnecting wire with 105C, 600V, 2/64” insulation.
The Infinity control will respond to cooling and heating demands
with the maximum safe airflow based on electric heat size (if
applicable) and unit capacity.
50X
T
--
A
