Hussmann USL-2, Installation And Service Instructions Manual

Page 8 

Because of the CFC atmospheric considerations 
being  taken today, we ask that leak testing be 
done with refrigerant 22 mixed with nitrogen.  If 
the condensing unit nameplate designates a re-
frigerant  other than R-22, remove all R-22 from 
the immediate area to avoid confusion after leak 
testing and evacuating the unit.  Recharge the 
unit with proper refrigerant. 
 
LEAK TESTING –  
 
 

The test gas cylinder must be equipped 

with a pressure gauge and regulator so that sys-
tem test pressures do not exceed maximum allow-
able limits.  Do not ever use anything other than a 
R-22/Nitrogen mixture for leak testing. 
 
 

Attach a refrigerant test gas cylinder to 

your service manifold and connect the manifold 
to the charging port on the liquid line valve.  
Charge an R-22/Nitrogen mixture into the sys-
tem, raising the pressure to the unit’s nameplate 
for the low side and high side pressures.  Using an 
electronic detector, carefully check the entire sys-
tem for leaks.  Take special care to inspect all 
brazed and flare connections. 
 
EVACUATION –  
 
 

After the system is proven leak tight, thor-

oughly evacuated the system according to the fol-
lowing procedure: 
 
1.  Discharge the refrigerant-nitrogen mixture, 

allowing it to blow from the system as rapidly 
as possible, into an empty cylinder.  Be sure 
that all service valves and solenoid valves are 
open to allow all of the mixture to be dis-
charged. 

2.  Connect a deep-drain vacuum pump to 

both the high and low side of the sys-
tem.  Pull a vacuum on the system to at 
least 1500 microns. 

 
3.  Break the vacuum by adding refriger-

ant into the system until the pressure is 
above 0 PSIG.  Always charge the re-
frigerant line into the system through a 
new drier in the charging manifold line.  
A 16 cubic inch drier is sufficient for 
this purpose. 

 
4.  Repeat steps 2 and 3 two more times, 

the third time evacuating the system to 
500 microns. 

 
OPERATING DATA –  
 
 

The following is typical data for 

USL models based on lab tests, and may 
vary under field operating conditions. 
 

Ambient Temperature   

75ºF 

Head 

Pressure 

  225 

psi 

Suction 

Pressure 

  3-5 

psi 

Discharge 

Air 

  -25ºF 

Return 

Air 

  -10ºF 

COMPRESSOR –  
 
 

The compressor is mounted on 

springs and banded for shipping purposes 
and this band needs to be cut upon installa-
tion.  DO NOT LOOSEN THE COM-
PRESSOR MOUNTING BOLTS AS 
THESE ARE FACTORY PRE-SET FOR 
PROPER RIDING ON THE SPRINGS. 
 
RECEIVER –  
 
 

The receiver should not be confused 

for a filter-drier or muffler.  The receiver is