York YCUL0045E, Installation Operation & Maintenance

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JOHNSON CONTROLS
17
FORM 150.63-NM8 (1020)
1
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 many cases a double
suction riser must be installed to ensure reliable oil
return at reduced loads. Table 5 & 6 indicates when
a double suction riser should be used for listed pipe
sizes to provide adequate oil return at reduced loads.
The calculated information was based on maintaining
a minimum of 1000 fpm (5.08 m/s) refrigerant vapor
velocity at full load.
Condenser Below Evaporator
When the condensing unit is located below the evapo-
rator, 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 pressure drops due to driers, valves, etc.
OIL TRAPS
All horizontal suction lines should be pitched at least
1/4" per foot (2 cm/m) in the direction of the refrigerant
flow to aid in the return of oil to the compressor. All
suction lines with a vertical rise exceeding 3 feet (.91
meters) should have a “P” trap at the bottom and top
of the riser to facilitate oil return. Suction lines with a
vertical rise exceeding 25 feet (7.6 meters) should be
trapped every 15 feet (4.6 meters).
F
or more details, refer to ASHRAE Refrigeration Hand-
book. System Practices for Halocarbon Refrigerants.
On systems where oil return is a prob -
lem, oil separators may be required.
However, if piping design is poor, even
with a separator, oil may be lost into
the system over time, which may cause
compressor failure.
REFRIGERANT CHARGE
The condensing unit is charged with nitrogen a hold-
ing charge. The 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.
70% of the calculated charge must
be added prior to starting a system.
Failure to add 70% of the charge may
cause compressor overheating when
the system is first started.
Final adjustment 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/ SIGHT GLASSES/ TXV'S
Liquid line filter driers, sight glass, and TXV's are field
supplied for each refrigerant circuit.
REFRIGERANT PIPING REFERENCE
For more details, refer to ASHRAE Refrigeration Hand-
book, Chapter 2.
TABLE 1
–
FITTING EQUIVALENT LENGTHS
*COPPER FITTING EQUIVALENT LENGTHS
LINE SIZE O.D.
SHORT-RADIUS ELL LONG-RADIUS ELL
3/4" (19mm) 6.5 ft. (2m) 4.5 ft. (1.4m)
7/8" (22mm) 7.8 ft. (2.4m) 5.3 ft. (1.6m)
1-1/8" (29mm) 2.7 ft. (.8m) 1.9 ft. (.6m)
1-3/8" (35mm) 3.2 ft. (1m) 2.2 ft. (.7m)
1-5/8" (41mm) 3.8 ft. (1.2m) 2.6 ft. (8m)
2-1/8" (54mm) 5.2 ft. (1.6m) 3.4 ft. (1m)
2-5/8" (67mm) 6.5 ft. (20m) 4.2 ft. (1.3m)
TABLE 3
–
MISCELLANEOUS LIQUID LINE
PRESSURE DROPS
*MISCELLANEOUS LIQUID LINE PRESSURE
SOLENOID VALVE 2 TO 3 PSI (13.8 TO 20.7 kPa)
FILTER/DRIER 2 TO 3 PSI (13.8 TO 20.7 kPa)
SIGHT GLASS 0.5 PSI (3.4 kPa)
TABLE 2
–
REFRIGERANT PIPING CHARGES
REFRIGERANT LINE CHARGES
SUCTION LINES LIQUID LINES
1-3/8" (35mm) .2 oz./ft. (6 grams/30cm) 3/4" (19mm) 2.7 oz./ft. (76 grams/30cm)
1-5/8" (41mm) .3 oz./ft. (8 grams/30 cm) 7/8" (22mm) 3.7 oz./ft. (105 grams/30cm)
2-1/8" (54mm) .6 oz/ft. (17 grams/30cm) 1-1/8" (29mm) 6.2 oz./ft. (176 grams/30cm)
2-5/8" (67mm) .8 oz./ft. (23 grams/30cm) 1-3/8" (35mm) 8.6 oz./ft. (244 grams/30cm)
* Pressure drops or equivalent length values are approximate. If more precise value is desired, consult either the York DX Piping Guide (form
050.40-ES2) or ASHRAE Refrigerant Handbook.
* Pressure drops or equivalent length values are approximate.
If more precise value is desired, consult ASHRAE Refrigerant
Handbook.