FORM QCC3-EG1 (517)
QUANTECH
51
Mounting holes (11/16” diameter) are provided in the steel channel for bolting the unit to
its foundation. See
Dimension Drawings on page 26
.
For ground level installations, precautions should be taken to protect the unit from tam-
pering by or injury to unau thorized persons. Screws on access panels will prevent casual
tampering; however, further safety precautions, such as unit enclosure options, a fenced-
in enclosure, or locking devices on the panels may be advisable. Check local authorities
for safety regulations.
REFRIGERANT PIPING
When sizing refrigerant pipe for split system air condition ing, consideration must be given
to the: (1) Suction line pressure drop due to friction, (2) Liquid line pressure drop due to
friction, (3) Suction line velocity for oil return, and (4) Liquid line pressure drop due to
vertical rise.
On a system where the evaporator blower is located below the condensing unit, the suc-
tion line must be sized for both pressure drop and oil return.
When the condensing unit is located below the evapora tor blower, the liquid line must be
designed for pressure drop due to friction loss and vertical rise. If the pressure drop due to
vertical rise and friction loss exceeds 30 psig (2.1 barg), some refrigerant will flash before
it reaches the thermal expansion valve.
All horizontal suction lines should be pitched at least 1/4 inch (6 mm) per foot in the direc-
tion of the refrigerant flow to aid the return of oil to the compressor. All suction lines with
a vertical rise exceeding 3 feet (1 m) should have a ‘P’ trap at the bottom and the top to
facilitate oil return. Suction lines with a vertical rise exceeding 25 feet (7.6 m) should be
trapped every 15 feet (4.6 m) to provide drain points for the oil when the circuit is deacti-
vated. When the circuit is reactivated, oil will return to the compressor more quickly and
in smaller slugs.
For more details, refer to ASHRAE Refrigeration Hand book, System Practices for Halo-
carbon Refrigerants.
Application Data (Cont'd)
Summary of Contents for QCC3
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