Discharge (Hot Gas) Line Sizing - Conair EP2 series User Manual

Table 2 – Liquid Line Sizes for R410A (continued)
40 Ton Circuit (R410A) Liquid Line Size (Inch OD)
Equivalent Horizontal or
Length (Ft) Down Flow
25 1 3/8
50 1 3/8
75 1 3/8
100 1 3/8
125 1 3/8
150 1 3/8
175 1 3/8
200 1 3/8
225 1 3/8
250 1 3/8
275 1 3/8
300 1 3/8

Discharge (Hot Gas) Line Sizing

The discharge line sizes depend 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 need to have a trap at the
bottom and reverse trap at the top. In addition, a
trap and reverse trap arrangement needs to be
spaced every 15 feet in the rise for oil management
(see Figure 6).
The discharge lines should pitch 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 unit
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. Take careful
consideration in the design of the discharge gas
riser.
Check the oil-level sight glass in the compressor to
ensure it is at the appropriate level to verify there is
Up Flow (Feet of Run)
0 to 5 6 to 10 11 to 15
1 3/8 1 3/8 1 3/8
1 3/8 1 3/8 1 3/8
1 3/8 1 3/8 1 3/8
1 3/8 1 3/8 1 3/8
1 3/8 1 3/8 1 3/8
1 3/8 1 3/8 1 5/8
1 3/8 1 3/8 1 5/8
1 3/8 1 3/8 1 5/8
1 3/8 1 3/8 1 5/8
1 3/8 1 3/8 1 5/8
1 3/8 1 3/8 1 5/8
1 3/8 1 3/8 1 5/8
no trapping of oil in the piping. The chiller is
equipped with hot-gas bypass capacity control and
the gas in the upflow discharge lines may have
problems moving the oil against gravity when
completely unloaded if a single rise system is used.
We recommend 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 3and 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.
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