15
SERVICING AND MAINTENANCE
cont.
Adjusting Sub-cooling and Superheat
Temperatures:
The system is
overcharged
if:
1.
the sub-cooling temperature is too high
and
2.
the evaporator is fully loaded (low loads on
the evaporator result in increased sub-cooling)
and
3.
the evaporator superheat is within the
temperature range as shown in TABLE 1 (high
superheat results in increased sub-cooling)
Correct an overcharged system by reducing the
amount of refrigerant in the system to lower the
sub-cooling.
The system is
undercharged
if:
1.
the superheat is too high
and
2.
the sub-cooling is too low
• Correct an undercharged system by adding
refrigerant to the system to reduce superheat and
raise sub-cooling.
• If the sub-cooling is correct and the superheat is
too high, the TXV may need adjustment to
correct the superheat.
Special Charging Instructions:
• For units equipped with low ambient refrigerant
flood back option being charged in the summer
when the ambient temperature is warm:
Once enough charge has been added to get the
evaporator superheat and sub-cooling values to
the correct setting more charge must be added.
Add approximately 80% of the receiver tank
volume to the charge to help fill the receiver
tank. The additional charge is required for the
system when running in cold ambient conditions.
• For units equipped with low ambient refrigerant
flood back option being charged in the winter
when the ambient temperature is cold:
1.
Once enough charge has been added to get the
evaporator superheat and sub-cooling values to
the correct setting more charge may need to be
added. If the ambient temperature is 0°F no
more charge is required. If the ambient
temperature is around 40°F add approximately
40% of the receiver tank volume.
2.
The unit will have to be checked for proper
operation once the ambient temperature is above
80°F.
Lubrication:
• All original motors and bearings are furnished
with an original factory charge of lubrication.
Certain applications require bearings be re-
lubricated periodically. The schedule will vary
depending on operating duty, temperature
changes, or severe atmospheric conditions.
• Bearings should be re-lubricated at normal
operating temperatures, but not when running.
Rotate the fan shaft by hand and add only enough
grease to purge the seals.
DO NOT
OVERLUBRICATE.
Service Information:
If the unit will not operate correctly and a service
company is required, only a company with
service technicians qualified and experienced in
both condensing units and air conditioning are
permitted to service the systems to keep
warranties in effect. If assistance is required, the
service technician must contact AAON.
Note: Service technician must provide the
model and serial number of the unit in all
correspondence with AAON.
Replacement parts for AAON equipment may be
obtained from AAON. When ordering parts,
always reference the unit model number, serial
number and part number.
