Fouling Factor (Cooler); Unit; Application Data - Carrier AQUAFORCE 30XA080-500 Product Data

Application data (cont)
Water loop volume
The volume in circulation must equal or exceed 3 gal. per
nominal ton (6.5 l/kW) of cooling for temperature stability
and accuracy in normal air conditioning applications. In
process cooling applications, or for operation at ambient
temperature below 32 F (0° C) with low loading condi-
tions, there should be from 6 to 10 gal. per ton (6.5 to
10.8 l/kW). To achieve this volume, it is often necessary to
install a tank in the loop.
Tank should be baffled to ensure there is no stratification
and that water (or brine) entering tank is adequately mixed
with liquid in the tank.
TANK INSTALLATION
BAD
BAD
Cooler fouling factor
The fouling factor used to calculate tabulated ratings is
⋅ hr ⋅ °F/Btu (.000018 m
0.001 ft 2
factor is increased, unit capacity decreases and compressor
power increases. Corrections to published ratings can be
approximated by using the following multipliers:
FOULING FACTORS
FOULING FACTOR FOULING FACTOR
(English) (SI)
⋅ hr ⋅ F/Btu) ⋅ °C/W)
(ft 2 (m 2
.00025 .000044
.00050 .000088
.00075 .000132
.00175 .000308
Cooler freeze protection
Freeze protection for the cooler is standard on all 30XA
air-cooled chillers. All units are equipped with cooler heat-
ers. Units are protected from freezing down to 0° F (–18 C)
through the cooler heaters and control algorithms. If a unit
controls the chilled water pump/valves, allowing for flow
through the cooler, the unit is protected from freezing
down to –20 F (–29 C). Since power is sometimes lost for
extended periods during winter storms, freeze protection
provided by heater tapes will be effective only if a back-up
power supply can be assured for the unit's control circuit,
heater and cooler pump. If not protected with an anti-
freeze solution, draining the cooler and outdoor piping is
recommended if the system will not be used during freezing
weather conditions.
46
GOOD
GOOD
⋅ °C/W). As fouling
2
COMPRESSOR
CAPACITY
POWER
MULTIPLIER
MULTIPLIER
0.991 0.995
0.977 0.987
0.955 0.979
0.910 0.952
Two conditions that must be considered when determin-
ing antifreeze concentration are both leaving water set
point and ambient freeze conditions. Both of these param-
eters can help determine the recommended concentration
level. Higher concentration must be used to adequately
protect the machine.
NOTE: Use only antifreeze solutions approved for heat ex-
changer duty.
For applications in which the leaving water temperature
set point is less than 40 F (4.4 C), a suitable inhibited anti-
freeze solution must be used. The solution concentration
must be sufficient to protect the chilled water loop to a
freeze protection (first crystals) concentration of at least
15° F (8.3° C) below the leaving water temperature set
point.
If the chiller refrigerant or fluid lines are in an area where
ambient conditions fall below 34º F (1.1º C), it is required
that an antifreeze solution be added to protect the unit and
fluid piping to a temperature of 15º F (8.3° C) below the
lowest anticipated ambient temperature.
Select concentration based on either burst or freeze pro-
tection as dictated by the application. If the chiller does not
operate during the winter, nor is a start-up expected, a
burst protection concentration is recommended. This con-
centration may not be high enough to pump the fluid
through the unit. Burst protection is typically a lower con-
centration that will provide better performance from the
machine. If the chiller does operate during winter, a freeze
protection concentration is recommended. This concentra-
tion will be high enough to keep the fluid in a condition
that it can be pumped at low ambient conditions.
IMPORTANT: Glycol anti-freeze solutions are highly
recommended since heater tapes provide no protection
in the event of a power failure.
Consult glycol fluid manufacturers for burst protection
recommendations and fluid specifications.
High ambient temperature operation
High outdoor ambient chiller start-up and operation is pos-
sible for standard 30XA chillers at ambient temperatures
up to 125 F (52 C) at nominal voltage.
Low ambient temperature operation
Units will start and operate down to 32 F (0° C) as
standard. Operation to –20 F (–29 C) requires optional
low ambient head pressure control as well as wind baffles
(field fabricated and installed to all units for operation
below 32 F [0° C]) if wind velocity is anticipated to be
greater than 5 mph (8 kp/h). Inhibited propylene glycol or
other suitable corrosion-resistant anti-freeze solution must
be field supplied and installed in all units for unit operation
below 34 F (1.1 C). Solution must be added to fluid loop to
protect loop down to 15° F (8.3° C) below minimum oper-
ating ambient temperature. Concentration should be based
on expected minimum temperature and either "Burst" or
"Freeze" protection levels. At least 6 gal per ton (6.5 l/kw)
of water volume is the recommended minimum for a mod-
erate system load.