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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
Water loop piping runs through unheated
areas or outside the building must be
insulated.
Never operate the unit in heat pump mode
with a saturated suction temperature below
35°F for pure water systems or below the
freezing point +3°F of the aqueous solution
of water and glycol.
Water Piping
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
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.
WATER PRESSURE
Prior to connection of the water
supply, verify water pressure is less
than maximu
unit nameplate. To prevent injury or
death due to instantaneous release
of high pressure water, drain valves
must
be field supplied on water
piping. Supply water connection may
require a backflow preventer to
prevent supply makeup water from
backing up into the public water
system.
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