Daikin RDT-135c Installation And Maintenance Manual page 41

RFS/RCS Permanent Split Systems
Piping Recommendations
Use type K or L clean copper tubing. Thoroughly clean or
1
braze all joints with high temperature solder. Make sure
nitrogen is flowing through the tubes while brazing to
minimize the formation of oxide contaminants.
2 Base piping sizes on temperature/pressure limitations as
recommended in the following paragraphs. Under no
circumstances should pipe size be based strictly upon coil
or condensing unit piping connection size.
Do not exceed suction line piping pressure drop equivalent
3
to 2°F (1°C), 3 psi (20.7 kPa) per 100 feet (30.5 m) of
equivalent pipe length. After the suction line size is
determined, check the vertical suction risers to verify that
oil will be carried up the riser and back to the compressor.
Pitch the suction line(s) in the direction of refrigerant flow
and make sure they are adequately supported. Lines should
be free draining and fully insulated between the evaporator
and the compressor. Install a trap on the vertical riser to the
compressor.
4 To determine the minimum tonnage required to carry oil up
suction risers of various sizes, check the vertical suction
risers using Table 12.
Size the liquid line for a pressure drop not to exceed the
5
pressure equivalent of 2°F (1°C), 6 psi (41.4 kPa)
saturated temperature. The RFS unit includes a factory
installed filter-drier, solenoid valve, and sightglass in
each liquid line, upstream of the thermostatic expansion
valve.
Table 12: Minimum tonnage (R-22 or R407C) to carry oil up
suction riser at 40°F saturated suction
Line size O.D.
1 1/8"
1 3/8"
1 5/8"
2 1/8"
2 5/8"
3 1/8"
3 5/8"
4 1/8"
Holding Charge
The RFS unit and RCS unit ship with a nitrogen holding
charge. At the time the unit was received, a visual inspection
of the unit piping should have been made to be sure no
breakage had occurred or that the fittings had not loosened. A
pressure test on the RCS units should indicate a positive
pressure in the unit. If no pressure is evident, the unit will have
to be leak tested and the leak repair ed. This should be noted
IM 738-2
Minimum tonnage
1.5
2.5
3.8
7.6
13.10
20.4
29.7
41.3
Mechanical Installation: RFS/RCS Permanent Split Systems
and reported to the Daikin sales representative and freight
carrier if the loss is due to shipping damage.
Before applying heat to remove brazed piping caps and plugs,
always vent piping to atmosphere. Failure to do so can cause
hazardous pressures, explosion, severe personal injuries, or
death.
RCS—Vent to atmosphere by opening gauge ports at the
compressors and liquid line shutoff valves. Make sure manual
valves are not back seated to shut off the gauge ports.
RFS—Vent to atmosphere by cutting off the process tubes on
the suction line caps.
The RFS unit does not have gauge ports for pressure
measurement. If no positive pressure is detected when cutting
off the process tubes and removing the tubing caps, the unit
should be leak tested as described below, after the
interconnecting piping has been brazed in place. This test will
also confirm the integrity of the field braze joints.
Leak Testing
In the case of loss of the nitrogen holding charge, the unit
should be checked for leaks prior to charging the complete
system. If the full charge was lost, leak testing can be done by
charging the refrigerant into the unit to build the pressure to
approximately 10 psig and adding sufficient dry nitrogen to
bring the pressure to a maximum of 125 psig. The unit should
then be leak tested with halide or electronic leak detector.
After making any necessary repair, the system should be
evacuated as described in the following paragraphs.
Do not use oxygen or air to build up pressure. Explosion hazard
can cause severe personal injury or death.
Evacuation
After determining the unit is tight and there are no refrigerant
leaks, evacuate the system. Use a vacuum pump with a
pumping capacity of approximately 3 cu.ft./min. and the
ability to reduce the vacuum in the unit to at least 1 mm (1000
microns).
1 Connect a mercury manometer or an electronic or other
type of micron gauge to the unit at a point remote from the
vacuum pump. For readings below 1 millimeter, use an
electronic or other micron gauge.
2 Use the triple evacuation method, which is particularly
helpful if the vacuum pump is unable to obtain the desired
1 mm of vacuum. The system is first evacuated to
approximately 29" (740 mm) of mercury. Then add enough
refrigerant vapor to the system to bring the pressure up to 0
pounds (0 microns).
WARNING
WARNING
39