9
Table 2 – Liquid Line Sizes for R410A (continued)
40 Ton Circuit (R410A) Liquid Line Size (Inch OD)
Equivalent
Length (Ft)
Horizontal or
Down Flow
Up Flow (Feet of Run)
0 to 5
6 to 10
11 to 15
25
1 3/8
1 3/8
1 3/8
1 3/8
50
1 3/8
1 3/8
1 3/8
1 3/8
75
1 3/8
1 3/8
1 3/8
1 3/8
100
1 3/8
1 3/8
1 3/8
1 3/8
125
1 3/8
1 3/8
1 3/8
1 3/8
150
1 3/8
1 3/8
1 3/8
1 5/8
175
1 3/8
1 3/8
1 3/8
1 5/8
200
1 3/8
1 3/8
1 3/8
1 5/8
225
1 3/8
1 3/8
1 3/8
1 5/8
250
1 3/8
1 3/8
1 3/8
1 5/8
275
1 3/8
1 3/8
1 3/8
1 5/8
300
1 3/8
1 3/8
1 3/8
1 5/8
Discharge (Hot Gas) Line Sizing
The discharge line size depends on the velocity
needed to obtain sufficient oil return. It is very
important to minimize line length and restrictions to
reduce pressure drop and maximize capacity.
Upflow hot gas risers require a trap at the bottom
and reverse trap at the top. In addition, install a trap
and reverse trap arrangement spaced every 15 feet
in the rise for oil management (see Figure 6).
Pitch the discharge lines downward, in the direction
of the hot gas flow, at the rate of ½ inch per each 10
foot of horizontal run. If the chiller is below the
condenser, loop the discharge line to at least 1 inch
above the top of the condenser. Install a pressure
tap valve at the condenser to facilitate measuring
pressure for service.
Check the oil-level sight glass in the compressor to
ensure it is at the appropriate level to verify there is
no trapping of oil in the piping. Use a double riser
system to ensure proper oil return under low load
operation. See Figure 7 and Table 4 for double riser
constructions.
Figure 6 – Vertical Riser Traps
Figure 7 - Double Discharge Riser
Note: Discharge line sizing shown in Table 3 and
Table 4 are listed per circuit and apply where leaving
water temperature (LWT) is 40°F or higher. For
applications where LWT is below 40°F, size lines using
the ASHRAE Refrigeration Handbook or other suitable
design guide.