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16
2.5.2 Pre-Charged Line Sets
Liebert pre-charged line sets are available in 15 ft (4.5m) and 30 ft (9m) lengths (see Table 7).
NOTICE
Risk of improper handling and installation of pre-charged lines. Can cause kinks and similar
damage to lines.
Care must be taken to prevent kinking the pre-charged lines for 1-ton and 3.5-ton units.
Use tube benders and make all bends before making connections to either end of the pre-
charged pipes. Coil any excess tubing in a horizontal plane with the slope of the tubing toward
the condensing unit. Use a soft, flexible material to pack around the tubes when sealing
openings in walls to prevent tube damage and to reduce vibration transmission.
2.5.3 Field-Fabricated Line Sets
All field-fabricated refrigeration piping should be copper piping, brazed using a brazing alloy with a
minimum temperature of 1350°F (732°C), such as Sil-Fos. Use a flow of dry nitrogen through the pip-
ing during brazing to prevent formation of copper oxide scale inside the piping. Avoid soft solders such
as 50/50 or 95/5.
Use the sweat adapter kits to terminate the piping at each unit end. Consult factory representatives
to obtain the proper sweat adapter kit. Table 8 has PFH unit connection sizes. Use Table 9 for rec-
ommended line sizes.
Prevailing good refrigeration practices should be employed for piping supports, leak testing, evacua-
tion, dehydration and charging of the refrigeration circuits. The refrigeration piping should be iso-
lated from the building by the use of vibration-isolating supports. Use a soft, flexible material to pack
around the tubes when sealing openings in walls to prevent tube damage and to reduce vibration
transmission.
Before connecting units together with field-fabricated piping, check for leaks and dehydrate
the field piping as follows:
1. Pressurize the field piping to 150 psig (1034 kPa) using dry nitrogen with a trace of refrigerant.
Check system for leaks with a suitable leak detector.
2. After completion of leak testing, release the test pressure (per local code) and triple evacuate the
field piping to 250 microns or lower, breaking the vacuum between the first two evacuations with
dry nitrogen.
3. After the third evacuation, verify 250 microns is maintained for at least one minute after the
piping is isolated from the vacuum pump by a shutoff valve.
Field piping is now ready to be installed between evaporator and condensing units.
Table 7 Refrigerant charge in Liebert pre-charged R-407C line sets
Line Size,
in.
Length,
ft. (m)
Charge R-407C,
lb-oz (kg)
3/8 liquid
15 (4.5) 0-5 (0.14)
30 (9) 0-10 (0.28)
5/8 or 7/8
suction
15 (4.5) 0-5 (0.14)
30 (9) 0-10 (0.28)