McQuay RoofPak RAH 047C, Руководство по установке и обслуживанию

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28 McQuay IM 487-4
Introduction
Piping Recommendations
1
Use type K or L clean copper tubing. Thoroughly clean or
braze all joints with high temperature solder.
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.
3
Do not exceed suction line piping pressure drop equivalent
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 6.
5
Insulate suction lines inside the unit cabinet to prevent
condensation.
6
Size the liquid line for a pressure drop not to exceed the
pressure equivalent of 2°F (1°C), 6 psi (41.4 kPa)
saturated temperature.
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.
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).
3
Evacuate the system again to 29" (740 mm) of vacuum.
Repeat his procedure three times. This method is most
effective by holding system pressure at 0 pounds
(0 microns) for a minimum of 1 hour between evacuations.
The first pulldown removes about 90% of the
noncondensables; the second removes about 90% of that
remaining from the first pulldown. After the third
pulldown, only 1/10 of 1% of noncondensables remains.
Table 7 on page 29 shows the relationship between pressure,
microns, atmospheres, and the boiling point of water.
Table 6: Minimum tonnage (R-22) to carry oil up suction
riser at 40°F saturated suction
Line size O.D. Minimum tonnage
1 1/8" 1.5
1 3/8" 2.5
1 5/8" 3.8
2 1/8" 7.6
2 5/8" 13.10
3 1/8" 20.4
3 5/8" 29.7
4 1/8" 41.3
WARNING
Do not use oxygen or air to build up pressure. Explosion hazard
can cause severe personal injury or death.
CAUTION
Before replacing refrigerant sensors or protective devices, see
“Experience in the field has shown that R-407C systems can be
“topped off” after a leak has been repaired and operate
normally. There is no need, except in the case of a critically
charged systems, to replace the entire charge after a leak has
been repaired.” on page 109 for an important warning to
prevent an abrupt loss of the entire charge.
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