NOTICE
Risk of oil contamination with water. Can cause equipment damage.
Liebert® DSE systems require the use of POE (polyolester) oil. POE oil absorbs water at a much faster rate
when exposed to air than previously used oils. Because water is the enemy of a reliable refrigeration system,
extreme care must be used when opening systems during installation or service. If water is absorbed into the
POE oil, it will not be easily removed and will not be removed through the normal evacuation process. If the oil
is too wet, it may require an oil change. POE oils also have a property that makes them act as a solvent in a
refrigeration system. Maintaining system cleanliness is extremely important because the oil will tend to bring
any foreign matter back to the compressor.
6.2.1 Refrigerant Piping Guidelines for Air Cooled Systems
•
Field installed interconnecting piping should be properly selected based on local codes and unit labeling.
•
Air cooled units ship with a nitrogen holding charge. Do not vent the charge until all refrigerant piping is in
place, ready for connection to the unit and condenser.
•
Use copper piping with a brazing alloy with a minimum temperature of 1350°F (732°C), such as Sil-Fos. Avoid
soft solders, such as 50/50 or 95/5.
•
Use a flow of dry nitrogen through the piping during brazing to prevent formation of copper oxide scale inside
the piping. When copper is heated in the presence of air, copper oxide forms. POE oils will dissolve these
oxides from inside the copper pipes and deposit them throughout the system, clogging filter driers and
affecting other system components.
•
A pure dry nitrogen flow of 1-3 ft
3
/min (0.5-1.5 l/s) inside the pipe during brazing is sufficient to displace the air.
Control the flow using a suitable measuring device.
•
Ensure that the tubing surfaces to be brazed are clean and that all burrs have been removed from the ends of
the tubes.
•
Ensure that all loose material has been cleaned from inside the tubing before brazing.
•
Protect all refrigerant line components within 18 in. (460 mm) of the brazing site by wrapping them with a wet
cloth or with a suitable heat sink compound.
•
Isolate piping from building using vibration isolating supports.
•
The Liebert® MCV heat rejection skid cannot be installed below the evaporator.
•
The DA250 is used with a Liebert® MCV heat rejection skid with receiver tanks. For this system, the outlet of
the receivers on the outdoor Liebert® MCV heat rejection skid must be higher than the elevation of the
electronic expansion valves (EEVs) inside of the indoor unit. If the vertical height of the receiver outlet is
greater than 60 ft. (18.3m) above the EEV, consult the factory. Refer to DPN003965 in
•
The DA265 is used with a Liebert® MCV heat rejection skid with without receiver tanks. For this system, the
bottom of the condenser coil on the outdoor Liebert® MCV heat rejection skid must be higher than the
elevation of the EEV inside of the indoor unit. If the vertical height between the condenser coil bottom and the
EEV is greater than 60 ft. (18.3m), consult the factory. Refer to DPN005207 in
•
Install traps on hot gas (discharge) lines at the base of vertical risers over 5 ft. (1.5 m) and then for vertical rises
over 25 ft. (7.6 m), install a trap in 20 ft (6 m) increments or evenly-divided over the vertical rise. The DA250
with piping out the top of the unit has internally installed traps on the hot gas lines.
•
Pitch horizontal hot gas piping down at a minimum rate of 1/2 in. per 10 ft. (42 mm per 10 m) so that gravity will
aid in moving oil in the direction of refrigerant/oil flow.
•
Consult factory if piping run exceeds 200 ft. (61 m) linear length or 300 ft. (91 m) equivalent length.
6 Piping and Refrigerant Requirements
27
