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Piping
PIPING
Refrigerant Piping
The installing contractor is responsible for piping the condensing unit to the air handling unit. Acceptable piping sizes can be determined by
using LATS software.
Refrigerant Piping Guidelines
• Pipe sizes must be selected to meet installation conditions and not based on the connection sizes at the evaporator or condensing unit.
• Only clean ACR tubing should be used and all piping should follow any applicable codes.
• The air handling unit coils are pressurized and the copper caps must be punctured to permit a gradual escape of pressure prior to
unsweating the caps.
• To avoid exposing the coils to moisture, immediately couple the tubing to the DOAS unit.
• When making solder connections, ensure the dry nitrogen flows through the lines when the copper is heated to prevent oxidization inside of
the copper.
• When piping is complete, the interconnecting piping and the air handling unit must be leak checked and evacuated to 500 microns or less.
This will allow condenser shutoff valves to open and allow refrigerant to flow to the air handling unit.
• The DOAS should be charged based on the manual calculation of refrigerant charge, based on coil refrigerant volumes.
• The refrigerant reheat coil is to be connected to a separate outdoor unit than the main coil outdoor unit. Ensure not to cross circuits in the
reheat systems.
A properly installed pipe system will have sufficient support so that pipes will not sag during the life of the system. As necessary, place
supports closer for segments where potential sagging could occur. Maximum spacing of pipe supports shall meet local codes.
Piping Guidelines
Figure 7: Pipe Support at DOAS Unit
A
B
A + B ~ 12" – 19"
Max. 12"
~ 12" – 19"
Figure 8: Typical Pipe Support Location - Change in Pipe Direction
Refrigerant Pipe Connections
• DOAS units come with brazed connections.
Refrigeration system components contain very small capillary tubes, small orifices, electronic expansion valves, oil separators, and heat
exchangers that can easily become blocked.
While brazing, ALWAYS follow these guidelines:
• Keep pipe supplies capped, clean, and store in a dry location.
• Use a tubing cutter, do not use a saw to cut pipe. De-burr and clean all cuts before assembly. Blow clean the pipe with dry nitrogen prior to
assembly.
• Do not use flux, soft solder, or anti-oxidant agents. Use a 15% silver phosphorous copper brazing alloy to avoid overheating and produce
good flow.
• Protect refrigerant shut-off valves electronic expansion valves, unit case, insulation, and control components from excessive heat by using
a wet rag or a heat barrier spray product while brazing.
• While brazing, always use a dry nitrogen purge operating at a minimum pressure of three (3) psig and maintain a steady flow.
Summary of Contents for ARND20BDAR2
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