78
refrigerant circuit components. Any damage
to the equipment as a result of water freezing
in the condenser 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 the cooling mode, without the need for
head pressure control. If the EWT is expected
to be lower than 57°F or a more stable
operation is desired, a factory provided head
pressure control water valve option is
available.
Glycol solution must be used if ambient
temperatures are expected to fall below
freezing or if the loop entering water
temperature to the unit is below 50°F while
operating in the heating mode (heat pump
units only). Adding glycol to condenser water
causes an increase in pressure drop and also
results in a decrease in unit performance. A
minimum concentration of 20% glycol
solution is recommended.
Table 24 - Glycol Freezing Points
Water loop piping runs through unheated
areas or outside the building must be
insulated.
Water Piping
Water flow switch is installed between the
condenser water supply and return
connections. This sensor provides a signal to
the unit controller that water flow is present
in the refrigerant-to-water heat exchanger
and the unit can operate without damaging
unit components.
Table 25 - Standard Brazed Plate Heat
Exchanger Water Connections
Supply and Return
Connection Size
008, 010, 009, 011,
013, 015, 016, 018,
020
Only use approved water pipe material.
Avoid using galvanized material for water
lines/fittings as the material is corrosive and
may cause fouling of the water system.
Condenser water pump must be field sized
and installed between the cooling
tower/geothermal loop and self-contained
unit. Size the system in accordance with the
ASHRAE Handbook. Use engineering
guidelines to maintain equal distances for
supply and return piping and limit bend
radiuses to maintain balance in the system.
Balancing valves, permanent thermometers
and gauges may be required.
Prior to connection of condensing
water supply, verify water pressure is
less than maximum pressure shown
on unit nameplate. To prevent injury
or death due to instantaneous release
of high pressure water, relief 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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