START-UP
Use the Start-Up Checklist supplied at the end of this book, and
proceed as follows:
Step 1 -- Check for Refrigerant Leaks
LOCATE AND REPAIR REFRIGERANT LEAKS AND
CHARGE THE UNIT AS FOLLOWS:
1. Using both high- and low-pressure ports, locate leaks and
reclaim remaining refrigerant to relieve system pressure.
2. Repair leak following accepted practices.
NOTE: Install a filter drier whenever the system has been opened
for repair.
Step 2 -- Start-Up Cooling Section and Make
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 compressor when the outdoor temperature is
below 40°F (4°C).
Do not rapid-cycle the compressor. Allow 5 minutes between "on"
cycles to prevent compressor damage.
CHECKING COOLING CONTROL OPERATION
Start and check the unit for proper cooling control operation as
follows:
1. Place room thermostat SYSTEM switch in OFF position.
Observe that blower motor starts when FAN switch is
placed in ON position and shuts down within 30 seconds
when FAN switch is placed in AUTO position.
2. Place SYSTEM switch in COOL position and FAN switch
in AUTO position. Set cooling control below room
temperature. Observe that compressor, condenser fan, and
evaporator blower motors start and that valves shirts.
Observe that cooling cycle shuts down when control setting
is satisfied. Reversing valve (RV) remains energized.
3. Place system switch in HEAT position. Observe that
compressor, indoor fan and outdoor fan energize (Reversing
Valve is deenergized in heat pump heating mode). Set
control above room temperature. Observe that heating cycle
shuts down when control setting is satisfied.
4. When using an automatic changeover room thermostat,
place both SYSTEM and FAN switches in AUTO
positions. Observe that unit operates in Cooling mode when
temperature control is set to "call for cooling" (below room
temperature), and unit operates in Heating mode when
temperature control is set to "call for heating" (above room
temperature).
Step 3 -- Refrigerant Charge
Amount of refrigerant charge is listed on unit nameplate (also refer
to Table 1).
Unit panels must be in place when unit is operating during
charging procedure. Unit must operate a minimum of 15 minutes
before checking charge.
NO CHARGE -- Use standard evacuating techniques. After
evacuating system, weigh in the specified amount of refrigerant
(refer to Table 1).
LOW CHARGE COOLING -- Use Cooling Charging Charts, Fig.
16-21. Vary refrigerant until the conditions of the appropriate chart
are met. Note that charging charts are different from the type
normally used. Charts are based on charging the units to the correct
superheat for the various operating conditions. An accurate
pressure gage and temperature sensing device are required.
Connect the pressure gage to the service port on the suction line.
Connect temperature sensing device to the suction line near the
compressor and insulate it so that outdoor ambient temperature
does not affect reading.
TO USE COOLING CHARGING CHARTS
This method is to be used in cooling mode only. Take the outdoor
ambient temperature and read the suction pressure gauge. Refer to
charts to determine what the suction temperature should be. If
suction temperature is high, add refrigerant. If suction temperature
is low, carefully recover some of the charge. Recheck the suction
pressure as charge is adjusted.
EXAMPLE: (Fig. 16)
Outdoor Temperature ..................... 85 ° F (29 °C)
Suction Pressure ....................... 74 psig
Suction Temperature should be ............. 60 °F (16 ° C)
(Suction Temperature may vary _+5°F (2.8°C)
HEATING MODE CHARGE
Do not attempt to adjust charge by cooling methods while in heat
pump heating mode. Recover refrigerant and weigh in according to
unit data plate refrigerant data,
Step 4 -- Indoor Airflow and Airflow Adjust-
ments
NOTE: For cooling operation, the recommended airflow is 350
to 450 CFM for each 12,000 Btuh of rated cooling capacity.
Table 2 shows dry coil air delivery for horizontal discharge units.
Tables 3- 4 show pressure drops.
NOTE: Be sure that all supply- and return-air grilles are open,
free from obstructions, and adjusted properly.
ELECTRICALSHOCK HAZARD
Failure to follow this warning could result in personal
iniury or death.
Disconnect electrical power to the unit and install lockout
tag before changing blower speed.
Airflow can be changed by changing the lead connections of the
blower motor.
Units 50ZH024,036,048, and 060 blower motors are factory wired
for low speed operation. Units 50ZH030 and 042 are factory wired
for medium speed operation.
FOR 208/230-V -- The motor leads are color-coded as follows:
3-SPEED 2-SPEED
black = high speed black = high speed
blue = medium speed
red = low speed red = low speed
To change the speed of the indoor fan motor (IFM), remove the fan
motor speed leg lead from the indoor (evaporator) fan relay (IFR)
with units 024, 030, 042, 048 and 060 or the time delay relay
(TDR) on 036 size and replace with lead for desired blower motor
speed. Insulate the removed lead to avoid contact with chassis
parts.
11
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