Hussmann USL-2, Installation And Service Instructions Manual

Page 6 

boards.  For servicing convenience, access is 
gained by removing the top decorative panel 
and electrical box cover.  THE CABINET 
SUPPLY BREAKERS SHOULD BE DIS-
CONNECTED BEFORE REMOVING THE 
ENCLOSURE COVER. 
 
 

The cabinet electrical supply breakers 

should be disconnected before removing the 
enclosure cover, and before service work ore 
maintenance of any kind is performed. 
 
DEFROST TIME CLOCK –  
 
 

The timer is factory pre-set for one de-

frost cycle per day at 12:00 a.m., with a 40 
minute failsafe.  The timer must be adjusted 
to the proper time of day when the cabinet is 
started.  The timer is adjusted by turning the 
knurled adjustment knob in the center of the 
dial face counter-clockwise until the time indi-
cator corresponds with the correct time of 
day. 
 
 

The defrost pins should be checked for 

tightness.  The timer will require re-adjusting 
after a power failure of the cabinet supply or 
if it is turned off for extended periods of time.  
If an additional defrost is required due to am-
bient or cabinet usage conditions, do not put a 
defrost during the middle of the day. 
 
 

Put any additional defrost during the 

night or at a time when the cabinet has the 
lowest usage. 
 
 

Defrost is time initiated and tempera-

ture terminated.  If the thermostat should fail, 
the timer is equipped with a failsafe set at 40 
minutes that will allow defrost to terminate on 
time. 

DEFROST HEATER THERMOSTAT –  
 
 

The defrost heater thermostat is 

clamped to the evaporator outlet tube.  It 
is a bi-metal thermostat that is tied in se-
ries with the evaporator fans for a delay 
and with defrost time clock solenoid to 
end defrost when the temperature has 
been satisfied.  The evaporator fans will 
not come on until the thermostat senses 
32ºF and defrost will terminate when the 
stat senses 58ºF. 
 
DEFROST HEATER REPLACEMENT 
–   
 

The defrost heaters are firmly em-

bedded in the evaporator and held in 
place with spring clips.  To remove the 
heater, first remove all the spring clips 
and pull the defective heater out of the 
slots in the evaporator, starting at the 
wire supply lead. 
 
 

The replacement heater should be 

firmly seated in the slots by using a small 
block of wood and a mallet.  After the 
new heater is in place, replace all of the 
spring retaining clips to assure heater re-
tention.  One lead of the defective heater 
may be used to pull the new leads 
through the cabinet to the respective ter-
minals as marked on each lead. 
 
 

NOTE:  Care must be taken to  

            make sure the drain stub is  
            correctly inserted in the cabinet 
            drain tube for proper drainage.