Specifications

APPLICATION DATA (cont)
1) 538D009,012 UNITS
(a) The 538D009,012 units are shipped with a full
charge of R-22 refrigerant. Check the charge
using the superheat method. Since all refriger-
ant lines are on the low side of the system, it is
not normally necessary to add or remove
charge.
(b) The 538D009,012 units have mixed-phase re-
frigerant flow in the liquid line. DO NOT install
a filter drier in the liquid line. The liquid line
must be insulated.
(c) No line size changes should be made on
538D009,012 units.
2) 538B AND 538D018,024 UNITS
(a) The 538B and 538D018,024 units are shipped
with a holding charge of R-22 refrigerant.
Charge is based on fan coil with smallest
charge and 25 ft of line. See Piston Guide
tables on page 67 for system charges. Add ad-
ditional charge by weight as necessary and
check the charge with a superheat calculator.
(b) For the 538B and 538D018,024 units, install
the filter drier provided with the unit in the liquid
line. A field-supplied moisture indicator may
also be used.
b. Long-lines applications, 538B and 538D018,024
units:
1) Liquid lines on these units should be
3
⁄ 8 in. only. DO
NOT resize liquid lines for additional length.
2) When sizing vapor line, determine line length by
finding equivalent ft of pipe. Equivalent line lengths
equal the linear length (measured length) of the in-
terconnecting vapor tubing plus losses due to el-
bows (see Fitting Loss in Equivalent Ft For Elbows
table below). If the number of elbows is not yet
known, assume 50% additional length for equiva-
lent length. In determining line size, be sure oil can
be properly returned to the compressor. Consult
the system design guide for proper oil return rec-
ommendations. For line lengths from 25 to 49 ft, no
special piping requirements are normally required.
Adjust charge to required amount by adding charge
per Step (g) on page 68 and checking superheat.
3) For line lengths over 50 ft:
(a) A crankcase heater should be added to scroll
compressor units (all non-scroll compressor
units have standard crankcase heaters).
Crankcase heaters help prevent refrigerant
migration to the compressor during the off
cycle.
FITTING LOSS IN EQUIVALENT FT FOR
ELBOWS
TUBE
SIZE
OD (in.)
90-DEGREE
SHORT
RADIUS
90-DEGREE
LONG
RADIUS
45-DEGREE
SHORT
RADIUS
5
⁄ 8 1.6 1.0 0.8
3
⁄ 4 1.8 1.2 0.9
7
⁄ 8 2.0 1.4 1.0
1
1
⁄ 8 2.6 1.7 1.3
(b) Any time the equivalent line length is over
100 ft, a liquid line solenoid must be used. A
liquid line solenoid may also be required for ver-
tical lift applications. See Step (f) on page 68,
and locate solenoid at the outdoor unit if required.
(c) A field fabricated wind baffle is recommended.
(d) The Effective Capacity Loss table on page 67
provides the estimated percentage of nominal
cooling capacity losses based on the standard
required vapor line size versus what is selected
for long-line applications. Heating capacity is not
generally affected by long-line applications.
Select the desired vapor line size from the Effec-
tive Capacity Loss table on page 67 based on
equivalent ft and desired vapor line size.
Subtract the nominal percentage loss from the
unit cooling capacities for the given indoor and
outdoor combination.
(e) Changes in piston size — The metering device
for a long-line application must be adjusted to
compensate for the frictional losses due to the
long refrigerant lines, refrigerant lines acces-
sories, and indoor coil above or below the out-
door unit. The AccuRaterT refrigerant metering
device pistons (heating and cooling) may need to
be changed to provide this adjustment. The
AccuRater piston should be changed for the
indoor unit and at the outdoor unit service valve
depending upon system configuration and line
length. Use the Change in Indoor and Outdoor
Unit Piston Size for Elevation tables on page 68
to determine correct AccuRater piston size. The
standard piston size is shown in the Piston Guide
tables on page 67.
Horizontal configuration — If the total equivalent
horizontal length is 100 ft or longer, the indoor
and outdoor pistons must be increased one full
piston size, in addition to the charge change in
Step (g), page 68. If exact size is not available,
use next smaller size per Chatleff Type B Com-
mon Piston Sizes table below.
Elevated configuration — After finding the appro-
priate change in piston size, add or subtract the
change from the original piston size number. If
the piston size is decreased, round down to the
next common piston size. If the piston size is in-
creased, round the new piston size up to the next
common piston size.
CHATLEFF TYPE B COMMON PISTON SIZES
PISTON SIZE PISTON SIZE PISTON SIZE
32 53 80
33 55 81
35 57 82
36 59 84
37 61 86
38 62 88
39 63 89
40 65 90
41 67 92
42 68 93
43 70 96
45 71 98
47 73 101
49 74 104
51 76 —
52 78 —
66