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REFRIGERANT SAFETY STANDARDS /
DEVICE CONNECTION LIMITATIONS
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 are allowed half of that concentration.
If a single zone 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 allow-
able concentration. Also consult state and local codes in regards to refrigerant safety.
Device Connection Limitations
A single-zone system consists of one outdoor unit and one indoor
unit. One of the most critical elements of a single-zone system is
the refrigerant piping. If the connection piping is not within allowable
limits, there will be reliability, performance, noise, and vibration
issues. The table below lists pipe length limits that must be followed
in the design of a Single Zone Four-Way Ceiling Cassette refrigerant
pipe system. Refer to the figures for maximum length and elevation
of piping.
Figure 23: Typical LC188HV, and LC249HV System Layout.
Max Length = A
Max Elevation = B
Indoor unit
164
A
B
Outdoor unit
Table 14: Single-Zone Four-Way Ceiling Cassette
System Model Name
Pipe Sizes
Pipe Length
(ELF = Equivalent
Length of Pipe)
Elevation
(All Elevation Limitations
are Measured in Actual
Feet)
Additional Refrigerant Needed (oz/ft)
28
Unit = Feet
Outdoor unit
164
A
B
Indoor unit
Refrigerant Piping System Limitations.
Vapor
Liquid
Standard length (no add'l refrigerant)
Longest total equivalent piping length
Shortest total equivalent piping length
Distance between fittings and indoor
or outdoor units
If outdoor unit is above indoor unit
If outdoor unit is below indoor unit
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Figure 22: Typical LC098HV and LC128HV System Layout.
Max Length = A
Max Elevation = B
Indoor unit
66
A
B
Outdoor unit
Figure 24: Typical LC349HV and LC429HV System Layout.
Max Length = A
Max Elevation = B
Indoor unit
246
A
B
Outdoor unit
LC098HV, LC128HV
LC188HV, LC249HV
3/8
1/4
24.6 feet
66 feet
16.4
49 feet
49 feet
0.22
Unit = Feet
Outdoor unit
66
A
B
Indoor unit
Unit = Feet
Outdoor unit
246
A
B
Indoor unit
LC369HV, LC429HV
5/8
5/8
3/8
3/8
24.6 feet
24.6 feet
164 feet
246 feet
16.4
16.4
98.4 feet
98.4 feet
98.4 feet
98.4 feet
0.43
0.43
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