Selection Procedure - Carrier AQUAFORCE 30XA080-500 Product Data

Selection procedure

Carrier's Packaged Chiller Builder Selection Program pro-
vides quick, easy selection of Carrier's air-cooled liquid
chillers. The program considers specific temperature, fluid
and flow requirements among other factors such as fouling
and altitude corrections.
Before selecting a chiller, consider the following points:
Leaving water temperature (LWT)
• If the LWT is less than 40 F (4.4 C), loop freeze protec-
tion to a minimum of 15° F (8.3° C) below the LWT set
point is required. The medium temperature brine option
is also required.
• If the LWT requirement is greater than 60 F (15.5 C), a
mixing loop is required.
Entering water temperature (EWT)
• If the EWT requirement is greater than 70 F (21.1 C), a
mixing loop is required. The EWT should not exceed
70 F (21.1 C) for extended operation. Pulldown can be
accomplished from 95 F (35 C).
Cooler flow rate or cooler delta-T:
• The cooler delta-T (EWT – LWT) must fall between
5 and 20° F (2.8 to 11.1° C).
• For larger or smaller delta-T applications, a mixing loop
is required.
• If the cooler flow is variable and the rate of change of
flow should not exceed 10% per minute, a loop
volume of greater than 3 gallons per ton (3.2 l/kW) is
recommended.
Cooler pressure drop:
• A high cooler pressure drop can be expected when the
cooler delta-T is low. A mixing loop can help to alleviate
this situation.
Alternatively, consider a reduced pass option for a lower
delta-T.
• A low cooler pressure drop can be expected when
cooler delta-T is high.
• Consider the plus-one-pass cooler option to increase
delta-T and performance.
Water quality, fouling factor:
• Poor water quality can increase the required cooler foul-
ing factor.
• Higher than standard fouling factors lead to lower
capacity and higher input kW from a given chiller size
compared to running the same application with better
quality water (and lower fouling factors).
Operation below 32 F (0° C):
• Low ambient temperature head pressure control is
required.
30
• Consider wind baffles if average wind speed is greater
than 5 mph (8 km/h).
• Consider higher loop volumes, 6 to 10 gallons per
nominal ton (6.5 to 10.8 l/kW).
• Loop freeze protection with glycol is strongly recom-
mended to a minimum of 15° F (8.3° C) below lowest
anticipated ambient temperature.
• Chilled water pump control is strongly recommended;
otherwise override capability is required.
Chiller idle below 32 F (0° C):
• Loop freeze protection with glycol is strongly recom-
mended to a minimum of 15° F (8.3° C) below lowest
anticipated ambient temperature.
• Chilled water pump control is strongly recommended;
otherwise override capability is required.
• Drain the cooler — This will require a small amount of
glycol for residual water. Cooler heaters will need to be
disconnected.
• Highest allowable ambient air temperature is 125 F
(52 C).
NOTE: It may be necessary to select the high ambient
option to obtain performance with ambient air tempera-
tures approaching 125 F (52 C).
Cooling capacity requirement:
• Do not oversize the chillers by more than 15% at design
conditions.
• If capacity control is required below the standard mini-
mum step of unloading, the minimum load control
option should be employed. (See Selection Guide.)
Coil corrosion requirements:
• Coastal application
• Industrial application
• Coastal/industrial application
• Urban application
• Farming
Temperature reset:
• Return water (standard)
• Outside air temperature (standard)
• Space temperature (accessory sensor required)
• 4 to 20 mA (requires an Energy Management Module)
Demand limit:
• 2-step (requires an Energy Management Module)
• 4 to 20 mA (requires an Energy Management Module)
• CCN Loadshed