I/O MANUAL Horizontal/Modular/Vertical/Rooftop AHU 2015pg
.
21
COMMERCIAL AIRE PRODUCTS 501 Terminal Road, Fort Worth TX 76106
Tel: 817-624-0820
If the job requirements specify suction accumulators, they must be separately purchased and field
installed.
Hot Gas Bypass Line
Hot Gas Bypass is available for use with DX systems that may experience low suction pressure during the
operating cycle. This may be due to varying load conditions associated with VAV applications or units
supplying a large percentage of outside air. The system is designed to divert refrigerant from the
compressor discharge to the low pressure side of the system in order to keep the evaporator from
freezing and to maintain adequate refrigerant velocity for oil return at minimum load.
Hot discharge gas is redirected to the evaporator inlet via an auxiliary side connector (ASC) to false load
the evaporator when reduced suction pressure is sensed.
Field piping between the condensing unit and
the evaporator is required.
Hot Gas Bypass Piping Considerations for Evaporator above Condensing Unit
Pitch the hot gas bypass (HGB) line downward in the direction of refrigerant flow, toward the
evaporator.
When installing hot gas bypass risers, a drain leg must be provided at the lowest point in the system.
The drain leg must be vertical, its diameter should be the same as the diameter of the riser, and it
should be 1 foot long. Install a sight glass in the drain leg for observation. Run an oil return line, using
1/8 inch capillary tube, 10 feet in length, from the drain leg to the suction line. Connect the oil return
line below the sight glass and 1 inch above the bottom of the drain leg.
HGB valves are adjustable. Factory HGB valve settings will be sufficient for most applications, but may
require slight adjustments for some applications, including some make up air applications.
R-410A REFRIGERANT TEMPERATURE-PRESSURE CHART
º F
PSIG
º F
PSIG
º F
PSIG
º F
PSIG
º F
PSIG
20
78.3
46
132.2
72
207.0
98
307.5
124
439.6
21
80.0
47
134.7
73
210.3
99
311.9
125
445.4
22
81.8
48
137.2
74
213.7
100
316.4
126
451.3
23
83.6
49
139.7
75
217.1
101
321.0
127
457.3
24
85.4
50
142.2
76
220.6
102
325.6
128
463.2
25
87.2
51
144.8
77
224.1
103
330.2
129
469.3
26
89.1
52
147.4
78
227.7
104
334.4
130
475.4
27
91.0
53
150.1
79
231.3
105
339.3
131
481.6
28
92.9
54
152.8
80
234.9
106
344.4
132
487.8
29
94.9
55
155.5
81
238.6
107
349.3
133
494.1
30
96.8
56
158.2
82
242.3
108
354.2
134
500.5
31
98.8
57
161.0
83
246.0
109
359.1
135
506.9
32
100.9
58
163.8
84
249.8
110
364.1
136
513.4
33
102.9
59
166.7
85
253.7
111
369.1
137
520.0
34
105.0
60
169.6
86
257.5
112
374.2
138
526.6
34
107.1
61
172.5
87
261.4
113
379.4
139
533.3
36
109.2
62
175.4
88
265.4
114
384.6
140
540.1
