550.38-N1Y
Unitary Products Group
9
®
The “TOTAL SYSTEM CHARGE” must be permanently
stamped on the unit data plate.
Total system charge is determined as follows:
1.
Determine outdoor unit charge from tabular data sheet.
2.
Determine indoor coil adjustment from tabular data
sheet.
3.
Calculate the line charge using the Tabular Data Sheet.
a.
Calculate total length of pre-charged lines for quick
connect units.
b.
Calculate over 15 feet of sweat lines for sweat con-
nect units.
NOTE: The charge for pre-charged lines should be included
in the system charge shown on the data plate but need
not be added to the system. If sweat connect lines are
used, the line charge over 15 feet should be included
on the data plate and must be added to the system.
4.
Total system charge = item 1 + item 2 + item 3.
5.
Permanently stamp the unit data plate with the total
amount of refrigerant in the system.
Use one of the following charging methods whenever addi-
tional refrigerant is required for the system charge.
Measurement Method
If a calibrated charging cylinder or accurate weighing device
is available, add refrigerant accordingly.
Check flare caps on service ports to be sure they are leak
tight. DO NOT OVERTIGHTEN (between 40 and 60 inch -
lbs. maximum).
Superheat Charging Method
NOTE: Use this method only during system maintenace and
repair.
1.
Operate system until temperatures and pressures stabi-
lize (minimum of 10 minutes).
2.
Measure and record indoor wet bulb (WB) temperature
using a sling psychrometer and the outdoor dry bulb
(DB) temperature using a thermometer.
3.
Measure and record the suction pressure at the suction
service valve port.
4.
Using Table 1 on page 12, note the superheat value cor-
responding to the intersection of the indoor wet bulb and
the outdoor dry bulb.
5.
With the superheat value obtained in step 4 and the suc-
tion pressure value from step 3, find the intersection of
the values in Table 2 on page 12. This is the required
suction tube temperature at the suction service valve.
6.
To bring the tube temperature in line with the required
value from Table 2, add refrigerant to the service port to
cause the tube temperature to fall and reclaim refrigerant
to cause the temperature to rise.
Check flare caps on Schrader fittings to be sure they are
tight. DO NOT OVERTIGHTEN (40-60 inch-lbs. maximum).
SYSTEM START-UP
ENERGIZE CRANKCASE HEATER
If this unit is equipped with a crankcase heater for the com-
pressor, a warning label with an adhesive back is supplied in
the unit installation instruction packet. This label should be
attached to the field supplied disconnect switch where it will
be easily seen. See below:
In order to energize the crankcase heater:- Set indoor two
stage cooling thermostat to "OFF" position.- Close the line
power disconnect to the unit.
Refrigerant charging should only be carried out by a
qualified air conditioning contractor.
Compressor damage will occur if system is improperly
charged. On new system installations charge system
per tabular data sheet for the matched coil and follow
guidelines in this instruction.
IMPORTANT
An attempt to start the compressor without at least 8
hours of crankcase heat will damage the compressor
