AAON ProFit WH Series, Installation Operation & Maintenance, Page: 21 / 48

21
Freezing Water in the Heat Exchanger
This product contains one refrigerant-to-
water heat exchanger. A refrigerant-to-water
heat exchanger contains refrigerant in one
passage and water in another passage. Water
is subject to freezing at 32°F. When water
freezes in a heat exchanger significant forces
are exerted on the components of the heat
exchanger where the water is confined.
Failure of the refrigerant-to-water heat
exchanger due to freezing will allow water to
enter the refrigerant circuit and will cause
extensive damage to the refrigerant circuit
components. Any damage to the equipment
as a result of water freezing in the refrigerant-
to-water heat exchanger is excluded from
coverage under AAON warranties and the
heat exchanger manufacturer warranties.
Unit is capable of operating with Entering
Water Temperatures (EWT) as low as 57°F
during cooling mode without the need for an
automatic flow regulating water valve. If the
EWT is expected to be lower than 57°F or
more stable operation is desired, an automatic
flow regulating water valve must be installed.
Glycol solutions are required if ambient
temperatures are expected to fall below
freezing or if the loop water temperature is
below 50°F while operating in the heating
mode with the design minimum flow rate.
Adding glycol causes an increase in pressure
drop resulting in a decrease in unit
performance. A minimum concentration of
20% glycol solution is required. The unit
controller contains dip switches to set the
loop glycol percentage. Set the glycol
percentage to the closest option available,
rounding down if needed.
The option selected will reset the Leaving
Water Temperature safety for the unit.
AAON will not be responsible for frozen
coaxial coils due to improper selection of
glycol percentage. See Leaving Water
Temperature Alarm section for more details.
Table 2 - Glycol Concentration
Freezing Points
% Glycol Ethylene
Glycol
Propylene
Glycol
0 32°F 32°F
20 18°F 19°F
30 7°F 9°F
Cleaning the cooling tower or water
loop with harsh chemicals such as
hydrochloric acid (muriatic acid),
chlorine or other chlorides, can
damage the refrigerant-to-water heat
exchanger. Care must be taken to
avoid allowing chemicals to enter the
refrigerant-to-water heat exchanger.
See Appendix A - Heat Exchanger
Corrosion Resistance for more
information. WATER FREEZING
Failure of the refrigerant-to-water heat
exchanger due to freezing will allow
water to enter the refrigerant circuit
and will cause extensive damage to
the refrigerant circuit components.
Any damage to the equipment as a
result of water freezing is excluded
from coverage under AAON
warranties and the heat exchanger
manufacturer warranties.
CAUTION WARNING