York MILLENNIUM YCUL0045SC, Установка, эксплуатация и обслуживание

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YORK INTERNATIONAL
12
REFRIGERANT PIPING
General – When the unit has been located in its final
position, the unit piping may be connected. Normal in-
stallation precautions should be observed in order to re-
ceive maximum operating efficiencies. System piping
should conform to ASHRAE guidelines. All piping de-
sign and installation is the responsibility of the user.
YORK ASSUMES NO WARRANTY RESPONSIBILITY
FOR SYSTEM OPERATION OR FAILURES DUE TO
IMPROPER PIPING OR PIPING DESIGN.
Filter driers and sight glasses are shipped loose for field
installation on each refrigerant circuit. Field refrigerant
piping can be connected to the condensing unit without
loss of the holding charge in the unit.
All expansion valves, liquid line solenoid valves, and re-
frigerant piping are field supplied and installed.
Table 4 lists refrigerant line connections sizes per unit
model number.
Refrigerant Line Sizing
Refrigerant piping systems must be designed to provide
practical line sizes without excessive pressure drops,
prevent compressor oil from being “trapped” in the refrig-
erant piping, and ensure proper flow of liquid refrigerant
to the thermal expansion valve. Considerations should
be given to:
1. Suction line pressure drop due to refrigerant flow.
2. Suction line refrigerant velocity for oil return.
3. Liquid line pressure drop due to refrigerant flow.
4. Liquid line pressure drop (or gain) due to vertical rise
of the liquid line.
Tables 5 & 6 provide the pressure drops for given pipe
sizes for both liquid and suction lines. The pressure
drops given are per 100 ft. (30.5 m) of refrigerant piping.
These friction losses do not include any allowances for
strainer, filter drier, solenoid valve, isolation valve, or
fittings.
Nominal pressure drop for solenoids, sight glass, and
driers are shown in Table 2.
Table 1 includes approximate equivalent lengths for cop-
per fittings.
To ensure a solid column of liquid refrigerant to the ex-
pansion valve, the total liquid line pressure drop should
never exceed 40 psi (276 kPa). Refrigerant vapor in the
liquid line will measurably reduce valve capacity and poor
system performance can be expected.
To allow adequate oil return to the compressor, suction
risers should be sized for a minimum of 1000 FPM (5.08
m/s) while the system is operating at minimum capacity
to ensure oil return up the suction riser. Refer to Tables 5
& 6 under column labeled “Nominal Tons (kW) Unloaded.
Evaporator Below Condensing Unit
On a system where the evaporator is located below the
condensing unit, the suction line must be sized for both
pressure drop and oil return. In some cases, a double
suction riser must be installed to ensure reliable oil re-
turn at reduced loads. Tables 5 & 6 indicate when a double
suction riser should be used for listed pipe sizes to pro-
vide adequate oil return at reduced loads. The calcu-
lated information was based on maintaining a minimum
of 1000 fpm (5.08 m/s) refrigerant vapor velocity.
Condenser Below Evaporator
When the condensing unit is located below the evapora-
tor, the liquid line must be designed for both friction loss
and static head loss due the vertical rise. The value of
static head loss of 5 psi/ft.(3.4 kPa/30 cm) must be added
to the friction loss pressure drop in addition to all pres-
sure drops due to driers, valves, etc.
Oil Traps
All suction lines with a vertical rise exceeding 3 feet (.91
meters) should have a “P” trap at the bottom and top
(inverted) of the riser. Suction lines with a vertical rise
exceeding 25 feet (7.6 meters) should be trapped every
15 feet (4.6 meters).
Refrigerant Charge
The condensing unit is charged with 6 lbs. (2.7 kg) of
R-22 for a holding charge. The remaining operating charge
for the condensing unit, evaporator coil, and refrigerant
piping must be “weighed-in” after all refrigerant piping is
installed, leak checked, and evacuated. Final adjust-
ment of refrigerant charge should be verified by subcooling
values (refer to section on Pre-Startup for checking
subcooling). See Table 3 for Refrigerant Line Charges.
Filter Driers
Liquid line filter driers and sight glass is factory supplied
for field installation on each refrigerant system.
Refrigerant Piping Reference
For more details, refer to ASHRAE Refrigeration Hand-
book, Chapter 2.
Installation