AAON M2-036 - Manual (Page 76)

76
Indoor Coils
Indoor cooling/evaporator coils must be
cleaned regularly to maintain unit efficiency
and operation. Dirty evaporator coils will
eventually freeze up and often result in a
time consuming and expensive service call.
Clean filters will help to prevent dirt from
accumulating on cooling coils, however
cooling coils should be cleaned at least
annually by an HVAC professional.
Refrigeration Cycle
Satisfactory performance of the refrigeration
cycle can be determined by measuring
suction line superheat. In order to determine
if refrigerant flowing from the evaporator is
dry, ensure that the system has enough
refrigerant to produce liquid line subcooling,
but not so much to cause abnormally high
condensing temperatures (and pressures).
Refrigerant cycle analysis is best performed
in conditions that approach the conditions
where the air conditioner will be expected to
operate.
E-Coated Coil Cleaning
Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage.
Surface loaded fibers or dirt should be
removed prior to water rinse to prevent
restriction of airflow. If unable to back wash
the side of the coil opposite of the coils
entering air side, then surface loaded fibers
or dirt should be removed with a vacuum
cleaner. If a vacuum cleaner is not available,
a soft non-metallic bristle brush may be used. In either case, the tool should be
applied in the direction of the fins. Coil
surfaces can be easily damaged (fin edges
bent over) if the tool is applied across the
fins.
Use of a water stream, such as a garden
hose, against a surface loaded coil will drive
the fibers and dirt into the coil. This will
make cleaning efforts more difficult. Surface
loaded fibers must be completely removed
prior to using low velocity clean water rinse.
A
monthly clean water rinse is
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides, dirt, and debris. It is very
important when rinsing, that water
temperature is less than 130°F and pressure
is than 900 psig to avoid damaging the fin
edges. An elevated water temperature (not to
exceed 130°F) will reduce surface tension,
increasing the ability to remove chlorides
and dirt.
Quarterly cleaning is essential to extend
the life of an e-coated coil and is required
to maintain coating warranty coverage.
Coil cleaning shall be part of the unit’s
regularly scheduled maintenance
procedures. Failure to clean an
e-coated coil
will void the warranty and may result in
reduced efficiency and durability.
Electric shock hazard. Shut off all
electrical power to the unit to avoid
shock hazard or injury from rotating
parts.
WARNING
High velocity water from a pressure
washer or compressed air should
only be used at a very low pressure
to prevent fin and/or coil damages.
The force of the water or air jet may
bend the fin edges and increase
airside pressure drop. Reduced unit
performance or nuisance unit
shutdowns may occur.
CAUTION