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Refrigerant Piping Installation
Proper system operation depends on the installer using best practices and utmost care while assembling the piping system as one of the
main causes of refrigerant leaks is defective connections. For VRF systems, the installer needs to know how perform both flared and brazed
connections successfully.
Flaring Practices
Flared fittings are used to connect the indoor units and heat recovery units to the refrigerant piping
system. Always use the proper size tool to finish the flare, creating a 45° flare (see table and diagram).
When connecting the flare nuts, coat the inside and outside with PVE refrigeration oil only. Hand tighten
the nuts at first, then, use a torque wrench and a backup wrench to finish. Avoid overtightening the flare
nuts.
Brazing Practices
Refrigerant piping system joints are brazed in the field. Multi V IV refrigeration system components
contain very small capillary tubes, small orifices, electronic expansion valves, oil separators, and heat
exchangers that can easily become blocked.
• Use adapters to assemble different sizes of pipe.
• Do not use flux, soft solder, or anti-oxidant agents; use a 15% silver phospho-
rous copper brazing alloy.
• Protect isolation valves, electronic expansion valves, and other heat-sensitive
control components from excessive heat with a wet rag or a heat barrier spray
product
During installation, it is imperative to keep the piping system free of contaminants and debris such as copper burrs, slag, or carbon dust.
Refrigerant Safety Standards
ASHRAE Standards 15-2010 and 34-2010 address refrigerant safety and the maximum allowable concentration of refrigerant in an occupied
space. Refrigerant will dissipate into the atmosphere, but a certain volume of air is required to safely dissipate the refrigerant. For R410A
refrigerant, the maximum allowable concentration of refrigerant is 26 lbs./1,000 cubic feet (Addendum L modified the RCL to 26) of occupied
spaces. Buildings with 24-hour occupancy allow half of that concentration.
If a VRF system develops a refrigerant leak, the entire refrigerant charge of the system will dump into the area where the leak occurs. To
meet ASHRAE Standards 15 and 34, the smallest room volume on the system must be calculated and compared to the maximum allowable
concentration. If the concentration level is higher than allowed, the following are some design suggestions to eliminate the problem:
• Split dual-frame and triple-frame systems into single-frame systems that have lower refrigerant charges.
• Add transfer grilles in the ceiling or walls of the smaller rooms to increase the volume of the room.
• Remove the smallest space from the system and serve it with a smaller mini-split system.
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LAYOUT BEST PRACTICES
General Information / Guidelines
Table 55: Flared Connection Dimensions.
Pipe
Indoor Unit
Vapor
(Btu/h)
(in. O.D.)
1/2
<54,600
5/8
3/4
Figure 44: Dimensions of the Flare.
90°
2
A
R=0.4~0.8
"A"
Liquid (in.
Vapor (in.)
Liquid (in.)
O.D.)
1/4
5/8 ~ 11/16
7/16 ~ 1/2
3/8
5/8 ~ 11/16
5/8 ~ 11/16
3/8
3/4 ~ 13/16
5/8 ~ 11/16
| 145
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