Table of Contents
Advertisement
Low- -Charge Cooling
Unit charging charts are used to diagnose and correct
incomplete (undercharged) conditions (and overcharged
conditions). The unit charging chart specific to this unit is
attached to the unit's compressor access panel.
Model 48TC units use two types of charging charts; one
type for Base Cooling systems and a different type for
most units equipped with Humidi- - MiZer systems. Check
your unit's info plate to confirm this unit's Model Number
and value in Position 6. A Position 6 value of A or D
indicates a unit with a base cooling system; see section
below for information on using these charts. A Position 6
value of B or E indicates a unit with Humidi- - MiZer
system; skip to the Humidi- - MiZer section below for
information on charging these systems.
SIZE DESIGNATION
04
05
06
07
08
09
12
14
16
EXAMPLE:
Model 48TC*A04
Outdoor Temperature
. . . . . . . . . . . . . . . . . .
Suction Pressure
. . . . . . . . . . . . . . . . .
Suction Temperature should be
Units with Base Cooling Systems (Position 6 =
A or D)
Charging charts for base cooling units (using Acutrol
refrigerant metering devices) are based on charging the
units to the correct superheat for the various operating
conditions. See Tables 2- - 4 for unit specific charging chart
figures.
NOTE: Unit size D14 has two charging charts, based on
outdoor coil type installed in this unit. Check the unit
infoplate for the value in Position 11, then select the
appropriate figures in Table 3.
Accurate pressure gauge and temperature sensing meter(s)
are required. Connect the pressure gauge to the service
port on the suction line. Mount one temperature sensing
device on the suction line and insulate it so that outdoor
ambient temperature does not affect the reading. Locate
the second temperature device (thermometer or meter
second channel sensor) in front of the largest face on the
outdoor coil to measure entering air temperature.
Indoor- - air flowrate (cfm) must be within the normal
operating range of the unit. If a Motormaster head
pressure control is on the unit, the output must be
jumpered to provide full speed operation on all outdoor
fans.
NOMINAL TONS
REFERENCE
3
4
5
6
7.5
8.5
10
12.5
15
85_F (29_C)
140 psig (965 kPa)
. . . . . . . . . .
60_F (16_C)
READING THE CHART (EXAMPLE):
Model 48TC*A04
Outdoor Temperature
. . . . . . . . . . . . . .
Suction Pressure
. . . . . . . . . . . . . .
Suction Temperature should be
Using the Base Cooling Charging Charts
Read the suction pressure gauge; record the pressure.
Read the outdoor ambient temperature and the suction line
temperature. Refer to unit chart to determine what suction
temperature should be and compare to test reading. If the
test suction temperature is higher than the chart value, add
refrigerant. If test suction temperature is lower than chart
value, carefully recover some of the charge. Recheck the
suction pressure as charge is adjusted.
Alternate method: Plot the test suction temperature (using
the X- - axis) and test suction pressure (using the Y- - axis)
on the unit charging chart. Locate the curve for the
outdoor ambient temperature. If the plotted test condition
point is to the right/below the outdoor ambient
temperature curve, add refrigerant. If the plotted test
condition is to the left/above the outdoor ambient
temperature curve, carefully recover some of the charge.
Recheck the suction pressure as charge is adjusted.
Allow the unit to operate for approximately five minutes,
then recheck conditions against the charging chart. Repeat
the charge adjustment procedure until the plotted test
condition falls on the appropriate outdoor ambient
charging curve.
When charging procedure is completed, remove the
jumper on the Motormaster control if used.
Units with Humidi- - Mizer Adaptive Dehumid-
ification System (Model Number Position 6 or
B or E)
Charging charts for Humidi- - MiZer units except sizes
E08- - E14 are based on charging the units to the correct
liquid temperature for the current discharge pressure
condition. Unit sizes E08- - E14 use the Base Cooling unit
charging charts but with a modified procedure. See
instructions below. See Tables 4 (sizes 04- - 07) and Table
3 (sizes 08- - 16) for unit specific charging chart figures.
To Use the Cooling Charging Charts, Units
with Humidi- -Mizer
NOTE: 48TC units equipped with Humidi- - MiZer option
include a Low Temperature Lockout temperature switch
(LTLO) that will prevent operation in Reheat1 or Reheat2
modes at outdoor temperature below 40_F (4.4_C). At
outdoor temperature below 40_F (4.4_C), perform charge
check using only Cooling mode operation and use the
standard cooling charging charts per Tables 2 and 3.
Return to site when the temperature is above 45_F
(7.2_C) to complete charge checks requiring unit
operation in Reheat1 or Reheat2 modes.
17
85_F (29_C)
140psig (965 kPa
. . . . .
60_F (16_C)
Advertisement
Table of Contents
