Application Data - Carrier AQUAFORCE 30XA080-500 Product Data

Application data

Chiller location and clearances
Do not locate near sound sensitive areas without proper
acoustic consideration. For applications requiring mount-
ing a chiller on a building rooftop, consideration should be
given to using rubber-in-shear or spring isolators to mini-
mize structure-borne transmission. Unit must be level when
installed to ensure proper oil return to the compressors.
Clearances must be provided around chillers for airflow,
service and local code requirements. See dimensional
drawings for specific unit clearance requirements. Ensure
adequate clearance between adjacent chillers is main-
tained. A minimum of 10 ft is recommended. Chiller fan
discharge must be at least as high as adjacent solid walls.
Installation in pits is not recommended.
Strainers
A strainer with a minimum screen size of 20 mesh must be
installed in the entering cooler fluid line, no more than
10 ft ahead of the cooler.
Oversizing chillers
Oversizing chillers by more than 15% at design conditions
must be avoided as the system operating efficiency is
adversely affected (resulting in greater or excessive electri-
cal demand). When future expansion of equipment is
anticipated, install a single chiller to meet present load
requirements and add a second chiller to meet the addi-
tional load demand. It is also recommended that 2 smaller
chillers be installed where operation at minimum load is
critical. The operation of a smaller chiller loaded to a
greater percentage over minimum is preferred to operating
a single chiller at or near its minimum recommended value.
Minimum Load Control should not be used as a means to
allow oversizing chillers. Minimum Load Control should be
given consideration where substantial operating time is
anticipated below the minimum unloading step.
Cooler water temperature
1. Maximum leaving chilled water temperature (LCWT)
for the unit is 60 F (15.5 C). Unit can start and
pull down with up to 95 F (35 C) entering-water
temperature. It is recommended that entering-water
temperature not exceed 70 F (21.1).
2. Minimum LCWT for a standard unit is 40 F (4.4 C).
For leaving-water temperatures between 15 and
39.9 F (–9.4 to 43 C) an inhibited antifreeze solution
is required. Application of chiller to 15 F (–9.4 C) is
possible by ordering the factory-installed medium
temperature brine option.
NOTE: Water flowing through cooler should not exceed
100 F.
Cooler flow/range
Ratings and performance data in this publication are for a
cooling temperature rise of 10° F (5.5° C). The 30XA chill-
ers may be operated at a different temperature rise, provid-
ing flow limits are not exceeded and corrections to system
guidelines are made. For minimum and maximum cooler
flow rates, see the Minimum and Maximum Cooler Flow
Rates table. A high flow rate is generally limited by the
maximum pressure drop that can be tolerated by the unit.
The 30XA chillers are designed for a full load temperature
rise of 5° to 20° F (2.8° to 11.1° C). Use the Packaged
Chiller Program to obtain the rating if a temperature rise
other than 10° F (5.5° C) is used.
Minimum cooler flow (maximum cooler tempera-
ture rise) — The minimum cooler flow for standard units
is shown in the Minimum and Maximum Cooler Flow
Rates table. When system design conditions require a
lower flow (or higher rise) than the minimum allowable
cooler flow, follow the recommendations below.
a. Multiple smaller chillers may be applied in series, each
providing a portion of the design temperature rise.
b. Cooler fluid may be recirculated to raise the flow rate to
the chiller. However, the mixed temperature entering
cooler must be maintained a minimum of at least 5 F
(2.8 C) above the LCWT.
NOTE: Recirculation flow is shown below.
RECIRCULATION FLOW
Maximum cooler flow — The maximum cooler flow
(approximately 5° F rise) results in a practical maximum
pressure drop through cooler.
Return fluid may bypass the cooler to keep the pressure
drop through the cooler within acceptable limits. This per-
mits a higher delta T with lower fluid flow through cooler
and mixing after the cooler.
NOTE: Bypass flow is shown below.
BYPASS FLOW
Variable cooler flow rates
Variable rates may be applied to a standard chiller. The unit
will, however, attempt to maintain a constant leaving
chilled water temperature. In such cases minimum flow
must be in excess of minimum flow given in the Minimum
and Maximum Cooler Fluid Flow Rates table, and mini-
mum water volume must be in excess of 3 gallons per ton
(3.2 l/kw). Flow rate must change in steps of less than
10% per minute. Apply 6 gal. or more per ton (6.5 l/kw)
water loop volume minimum if flow rate changes more
rapidly.
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