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Single Zone Extended Piping Wall Mounted Engineering Manual
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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.
REFRIGERANT SAFETY STANDARDS / 
DEVICE CONNECTION LIMITATIONS
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 the pipe length limits that must be 
followed in the design of a Single Zone Extended Piping 
Wall Mount refrigerant pipe system. Refer to the figure 
for maximum length and elevation of piping.
Figure 25: Single Zone Extended Piping System Layout.
Outdoor unit
Indoor unit
A
B
Outdoor unit
Indoor unit
A
B
Max Length = A
Max Elevation = B
Unit = Feet
Table 9: Single Zone Extended Piping Refrigerant Piping System Limitations.
Model Numbers LS243HLV3 LS303HLV3 LS363HLV3
Pipe Sizes
Vapor  5/8 inches 5/8 inches 5/8 inches
Liquid 3/8 inches 3/8 inches 3/8 inches
Pipe Length
(ELF = Equivalent Length 
of pipe in Feet)
Standard Piping Length 24.6 24.6 24.6
Piping Length with No Additional Refrigerant 24.6 24.6 24.6
Longest Total Equivalent Piping Length 164.0 164.0 164.0
Shortest Total Equivalent Piping Length 9.8 9.8 9.8
Distance between fittings and indoor units or outdoor units LQFKHV LQFKHV LQFKHV
Elevation  
(All Elevation Limitations 
are Measured in Actual 
Feet)
If outdoor unit is above indoor unit 98.4 98.4 98.4
If outdoor unit is below indoor unit 98.4 98.4 98.4
Additional Refrigerant Needed (oz./ft) 0.38 0.38 0.38