Suction Riser - Carrier Gemini 38AU 07 Series Installation, Start-Up And Service Instructions Manual
Air-cooled condensing units with puron r-410a refrigerant
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Table 10 — 38AUDC12 Hot Gas Bypass (HGBP) Piping Recommendations (Dual-Circuit)
MODEL AND
LINEAR LINE (FT)
NOMINAL
EQUIV. LINE (FT)
CAPACITY
Liquid Line Size (in.)
Pressure Drop (°F)
Max Lift (ft)
Pressure Drop (°F)
Suction Line Size (in.)
Circuit 1:
Tube S
Tube A
Pressure Drop (°F)
38AUDC12
Circuit 1:
Tube S
Tube A
Tube B
Pressure Drop (°F)
Circuit 1:
Circuit 2:
Pressure Drop (°F)
Charge (lb) 1/2
NOTES:
1. 38AUDC units require TWO sets of refrigeration piping.
Suction Riser
A suction riser condition exists when the outdoor unit is located
above the indoor (evaporator) unit and suction vapor must flow
vertically up to return to the compressor. Oil return is a concern
when the suction tube size is too large to produce the minimum re-
frigerant velocity to ensure oil return at minimum load conditions.
38AUZ (ALL) AND 38AUD (A,B) WITHOUT HGBP
Check Table 11 for maximum suction tube size for 38AU units at
minimum load conditions. Consider suction speed riser (reduced
tube size for vertical segment only) or double suction riser ar-
rangement if the planned suction tube size does not provide neces-
sary minimum flow-rates for this riser.
Table 11 — 38AU Maximum Suction Pipe Size
MODEL
UNIT SIZE
38AUZA, B
38AUZD, E
38AUDA, B
38AUDC
38AUDC12 WITH OPTIONAL HOT GAS BYPASS
Special consideration for suction riser requirements must be con-
sidered when applying this factory-installed hot gas bypass. It is
extremely important to consider the lowest possible refrigerant
tons of refrigerant flow when hot gas bypass is functioning to as-
sure proper oil return up suction risers.
Table 10 provides recommended tube sizes for model 38AUDC12
unit which includes the factory-installed hot gas bypass system on
Circuit 1. The selections in this table are based on evaluations of
system minimum load operating conditions for comfort cooling
applications, with compressor saturated suction pressure to 28°F
(–2.2°C) minimum.
0-24
0-37
3
/
8
1.8
25
3.8
5
/
in.
8
5
/
in
8
.
2.0
/
in.
5
8
/
in
5
8
.
NR
2.0
/
in
7
8
.
/
in
7
8
.
1.1
13.3
MAXIMUM TUBE SIZE
07
1
/
3
8
08
1
/
5
8
12
1
/
5
8
14
2
1
/
8
07
1
/
1
8
08
1
/
1
8
12
1
/
3
8
14
1
/
5
8
12
See Table 10
25-49
50-74
38-74
75-112
3
/
3
/
8
8
3.5
5.2
50
75
7.5
11.3
Vapor riser required, not greater than 20 ft (6.1 m) — See Fig. 5
1
1
/
in
1
3
/
in
8
.
8
.
5
/
in
5
/
in
8
.
8
.
2.0
1.9
Vapor riser greater than 20 ft (6.1 m) — See Fig. 6
/
in
/
in
7
7
8
8
.
/
in
/
in
5
5
8
8
1
/
in
5
/
in
2
.
8
.
1.6
1.7
No vapor riser required
/
in
1
/
in
7
1
8
.
8
.
/
in
1
/
in
7
1
8
.
8
.
2.1
0.9
14.3
15.8
2. For applications with equivalent length greater than 188 ft and/or
linear length greater than 125 ft (38 m), contact your local Carrier
representative.
Table 10 includes liquid line size selections based on use of RTPF
coil option only.
Table 10 includes three different suction line size selections for
Circuit 1 based on the elevation difference conditions between
the 38AUD unit and the evaporator coil location.
Outdoor Unit ABOVE Evaporator Coil
This installation will have at least one suction riser segment. If the
vertical elevation difference is less than 20-ft (6.1 m) linear feet
and requires only one or two segments, consider a speed riser se-
lection for Circuit 1; use the line marked VAPOR RISER RE-
QUIRED; NOT GREATER THAN 20 FT (6.1 M). See Fig. 5.
Tube S is the horizontal line size; tube A is the reduced diameter
riser size.
S
Fig. 5 — Suction Line Piping - Speed Riser
If the vertical elevation difference is greater than 20-ft (6.1-m) lin-
ear feet or requires more than two short lift segments, select the
Circuit 1 suction line size from Double Suction Riser lines data
under VAPOR RISER GREATER THAN 20 FT (6.1 M). See
Fig. 6. Tube S is the horizontal line size. Tube A is the reduced di-
ameter riser size without bottom trap; Tube B is the parallel riser
size with bottom oil trap.
10
75-99
113-149
3
/
1
/
8
2
8.7
1.2
65
100
12.2
9.4
1
3
/
in
8
.
5
/
in
8
.
2.0
1
/
in
1
8
/
in
5
8
5
/
in
88
1.7
1
/
in
1
8
.
1
/
in
1
8
.
1.2
16.9
20.0
A
20-FT (6.1 M)
MAX
LEGEND
A - Suction Riser With Trap
S - Suction Line to Condensing Unit
100-125
150-188
3
/
1
/
8
2
8.7
1.5
62
125
13.7
11.7
1
3
/
in
8
.
5
/
in.
8
2.0
1
/
in
1
8
/
in
5
8
5
/
in
8
.
2.1
1
/
in
1
8
.
1
/
in
1
8
.
1.5
18.1
22.0
CONDENSING
UNIT
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