I/O MANUAL Horizontal/Modular/Vertical/Rooftop AHU 2015pg
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COMMERCIAL AIRE PRODUCTS 501 Terminal Road, Fort Worth TX 76106
Tel: 817-624-0820
NOTE:
An oil trap must be installed in all vertical suction risers. An additional oil trap must be installed every
15’ for risers over 15’ high. If the condensing unit is located above the evaporator, an inverted oil trap
must be installed at the top of the vertical riser.
Piping from the condensing unit to the air handling unit is responsibility of the installing contractor. The
piping sizes must be selected to meet the codes and the actual installation conditions and not based on
connection sizes of the evaporator and/or condensing unit. Improper installation, adjustment,
alteration, service or maintenance, can cause property damage, personal injury or loss of life.
Installation and service must be performed by a trained and qualified technician.
Only clean ACR tubing should be used. Piping should conform to all the generally accepted practices and
codes. The AHU coils are shipped pressurized with nitrogen the copper caps must be punctured to allow
the gradual relief of the pressure prior to un-sweating the caps. Immediately couple the tubing to the
indoor unit to avoid exposing the coils to moisture. When making solder connections, make sure to have
dry nitrogen flowing through the lines to prevent copper oxidation inside the pipes.
Minimizing the refrigerant line size is favorable from an economic perspective, reducing installation
costs, and reducing the potential for leakage. However, as pipe diameters narrow, pressure-reducing
frictional forces increase.
Excessive suction line pressure drop causes loss of compressor capacity and increased power usage
resulting in reduced system efficiency. Excessive pressure drops in the liquid line can cause the liquid
refrigerant to flash, resulting in faulty TXV operation and improper system performance. In order to
operate efficiently and cost effectively, while avoiding malfunction, refrigeration systems must be
designed to minimize both cost and pressure loss.
Equivalent Line Length
All line lengths discussed in this manual, unless specifically stated otherwise, are Equivalent Line
Lengths. The frictional pressure drop through valves, fittings, and accessories is determined by
establishing the equivalent length of straight pipe of the same diameter.
Always use equivalent line
lengths when calculating pressure drop
. Special piping provisions must be taken when lines are run
underground, up vertical risers, or in excessively long line runs.
