AAON RN-140 - Manual (Page 87)

87
Evaporator Coil (6-25 and 30 ton)
Removal
Evacuate refrigerant from the systems.
Remove the TXV bulbs from the suction
lines. Disconnect the suction and liquid line
copper connections to the evaporator coil.
Figure 45 - Evaporator Coil Access
Remove the screws attaching the filter rack
to the evaporator coil blank-off panels at the
door opening and along the top of the coil.
Remove the screws attaching the filter rack
to the back wall. Angle filter rack away
from coil so it fits through the door opening.
It may be necessary to remove economizer
damper assembly.
Remove screws attaching access side, back,
and top blank-off panels to the evaporator
coil and the unit.
Angle the coil so that it fits through the door
opening.
Remove the evaporator coil.
Reinstallation
Install the coil in the unit drain pan. There
should be about a 1/4” gap between the
upstream side of the coil and the back of the
drain pan.
Secure the coil to the back wall of the unit
with the blank-off panel. Attach the top and
access side blank-off panels to the coil.
Attach the filter rack to the back, top, and
access side coil blank-off panels upstream of
the coil. Reinstall economizer damper
assembly if necessary.
Connect the suction and liquid copper
connections to the evaporator coil. Reinstall
the TXV bulbs on the suction lines.
Evacuate the refrigerant systems. Weigh in
the nameplate refrigerant charge.
See Adjusting Refrigerant Charge section to
check for proper sub-cooling and superheat
of the refrigerant systems.
Brazed Plate Heat Exchanger Cleaning
Because of a normally high degree of
turbulence in brazed plate heat exchangers,
for many applications the heat exchanger
channels are self cleaning. For applications
that are not self cleaning (i.e. hard water at
high temperatures, etc.) or applications
where additional cleaning is desired, it is
possible to clean the brazed plate heat
exchanger by circulating a cleaning liquid.
Use a tank with weak acid, 5% phosphoric
acid (H3PO4) or, if the exchanger is
frequently
cleaned, 5% oxalic acid
(H2C2O4). Pump the cleaning liquid
through the exchanger. For optimum
cleaning, the cleaning solution flow rate
should be a minimum of 1.5 times the
Electric shock hazard. Shut off all
electrical power to the unit to avoid
shock hazard or injury from rotating
parts.
WARNING