Brazed Plate Heat Exchanger Cleaning; E-Coated Coil Cleaning - AAON RN SERIES Installation Operation & Maintenance

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,
(H2C2O4). Pump
through the exchanger.
cleaning, the cleaning solution flow rate
should be a minimum of 1.5 times the
normal flow rate, preferably in a back-flush
mode. After cleaning, the heat exchanger
must be rinsed with clean water. A solution
of 1-2% sodium hydroxide (NaOH) or
sodium bicarbonate (NaHCO) before the last
rinse ensures that all acid is neutralized.

E-Coated Coil Cleaning

Documented routine cleaning of e-coated
coils is required to maintain coating
warranty coverage for fin and tube and
microchannel coils.
WARNING
Electric shock hazard. Shut off all
electrical power to the unit to avoid
shock hazard or injury from rotating
parts.
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
82
5% oxalic acid
the cleaning liquid
For optimum
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
recommended for coils that are applied in
coastal or industrial environments to help to
remove chlorides, dirt, and debris. It is very
important when
temperature is less than 130°F and pressure
is less than 100 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.
CAUTION
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
shutdowns may occur.
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
procedures. Failure to clean an e-coated coil
will void the warranty and may result in
reduced efficiency and durability.
water rinse
rinsing, that water
nuisance unit
maintenance
is