F. Metering Device — Long Line Cooling
In current equipment, all indoor units use a TXV with 15 to 30% bleed for metering in the cooling mode. This provides adequate
refrigerant migration protection for all cooling applications.
G. Piston Sizing — Heat Pumps Only
An AccuRater
TM
(fixed orifice) is used for refrigerant metering in the heating mode. This fixed expansion device must be changed from
the factory- supplied AccuRater
TM
based on indoor/outdoor vertical separation and system capacity. For horizontal applications up to
200 ft (61 m) linear length and 250 ft (76 m) total equivalent length, no heating piston change is necessary.
When sizing the heating piston for installations where the outdoor unit is below the indoor unit, use Table 9. When outdoor unit is
located above indoor unit, use Table 12.
Example: The factory supplied AccuRater
TM
for a single- stage 3- ton heat pump is a number 57. A system is installed with 200
equivalent ft of line set. Approximately 60 ft (18.3 m) is horizontal and the outdoor unit is 140 ft (42.7 m) above the indoor unit. Table
9 shows the AccuRater
TM
piston change to be +6. The new piston size is 57 + 6 = 63. If a 63 is not produced, round up to the next
larger available piston size.
On the same heat pump, if the outdoor unit was located 49 ft (14.9 m) below the indoor unit, Table 10 shows the piston change to be 57
- 2 = 55. If a 55 piston is not produced, round up to the next available size.
H. Liquid Line Solenoid — Long Line Heat Pump Heating
Since AccuRater
TM
do not provide off- cycle refrigerant migration protection in the heating mode, a liquid line solenoid is required for
single-stage and two- stage heat pump long line applications. Bi-flow solenoid valves provide flow control protection only in the
direction of the arrow molded into the valve.
The
arrow
must
point
toward
the
outdoor
unit
for off- cycle refrigerant control in the
heating mode. The arrow shows the direction of flow control. The solenoid should be installed within 2 ft. of the outdoor unit. The
liquid line solenoid kit number for a heat pump is KHALS0401LLS.
NOTE:
Equivalent length of the liquid line solenoid should be added to the total equivalent length of the tubing. See Table 2.
I. Charging Information
Use subcooling as the primary method for charging longline applications. Outdoor units are pre- charged for 15 ft (4.6 m) of 3/8 liquid
line. When using different length diameter liquid lines, charge adjustments are required. See Table 4 for charge adjustments required.
The charge adjustment will depend on the liquid line diameter used. See unit installation instructions for proper charging procedure.
For all long line applications, pressure drop and subcooling loss become a concern. In these applications, a
minimum of 10
°
F (5.6°C) of
subcooling
is required for all liquid line diameters to ensure no refrigerant flashing occurs before the TXV metering device.
Systems should be charged to 10°
_
subcooling or the rating plate subcooling, whichever is greater.
The amount of factory- charge can be found on the unit rating plate or in the Product Data literature. Long line applications do not
require additional oil charge.
VAPOR LINE SIZING AND COOLING CAPACITY LOSS
Acceptable vapor line diameters provide adequate oil return to the compressor while avoiding excessive capacity loss. The suction line
diameter shown in Table 3 is acceptable for AC and HP systems w i t h Puron refrigerant:
Table 3 - Vapor Line Sizing and Cooling Capacity Losses — Puron®
Refrigerant 1- Stage Air Conditioner Applications
Unit
Nominal
Size (Btuh)
Maximum
Liquid Line
Diameters
(In. OD)
Vapor Line
Diameters
(In. OD)
Cooling Capacity Loss (%) Total
Equivalent Line Length ft. (m)
26 --- 50
(7.9 --- 15.2)
51 --- 80
(15.5 --- 24.4)
81 --- 100
(24.7 --- 30.5)
101 --- 125
(30.8 --- 38.1)
126 --- 150
(38.4 --- 45.7)
151 --- 175
(46.0 --- 53.3)
176 --- 200
(53.6 --- 61.0)
201 --- 225
(61.3 --- 68.6)
226 --- 250
(68.9 --- 76.2)
18000
1 Stage
AC with
Puron
3/8
1/2
1
2
3
5
6
7
8
9
11
5/8
0
1
1
1
2
2
2
3
3
3/4
0
0
0
0
1
1
1
1
1
24000
1 Stage
AC with
Puron
3/8
5/8
0
1
2
2
3
3
4
5
5
3/4
0
0
1
1
1
1
1
2
2
7/8
0
0
0
0
0
1
1
1
1
30000
1 Stage
AC with
Puron
3/8
5/8
1
2
3
3
4
5
6
7
8
3/4
0
0
1
1
1
2
2
2
3
7/8
0
0
0
0
1
1
1
1
1
36000
1 Stage
AC with
Puron
3/8
5/8
1
2
4
5
6
8
9
10
12
3/4
0
1
1
2
2
3
3
4
4
7/8
0
0
0
1
1
1
1
2
2
42000
1 Stage
AC with
Puron
3/8
3/4
0
1
2
2
3
4
4
5
6
7/8
0
0
1
1
1
2
2
2
3
1 1/8
0
0
0
0
0
0
0
0
0
48000
1 Stage
AC with
Puron
3/8
3/4
0
1
2
3
4
5
5
6
7
7/8
0
0
1
1
2
2
2
3
3
1 1/8
0
0
0
0
0
0
0
1
1
60000
1 Stage
AC with
Puron
3/8
3/4
1
2
4
5
6
7
9
10
11
7/8
0
1
2
2
3
4
4
5
5
1 1/8
0
0
0
1
1
1
1
1
1
Applications
in
this
area
may
be
long
line
and
may
have
height
restrictions.
Page 26
Summary of Contents for 38C Series
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