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RLC-PRC016-EN18
Application
Considerations
Water Treatment
Dirt, scale, products of corrosion and
other foreign material will adversely
affect heat transfer between the water
and system components. Foreign matter
in the chilled water system can also
increase pressure drop and,
consequently, reduce waterflow. Proper
water treatment must be determined
locally, depending on the type of system
and local water characteristics.
Neither salt nor brackish water is
recommended for use in Trane air-
cooled Series R
™
chillers. Use of either
will lead to a shortened life to an
indeterminable degree. The Trane
Company encourages the employment
of a reputable water treatment specialist,
familiar with local water conditions, to
assist in this determination and in the
establishment of a proper water
treatment program.
The capacities given in the performance
data section of this catalog are based on
water with a fouling factor of .00010. For
capacities at other fouling factors, see
adjustment factors in Table F-1.
Effect Of Altitude On Capacity
Air-cooled Series R
™
chiller capacities
given in the performance data tables, P-1
through P-12, are for use at sea level. At
elevations substantially above sea level,
the decreased air density will decrease
condenser capacity and, therefore, unit
capacity and efficiency. The adjustment
factors in Table F-1 can be applied
directly to the catalog performance data
to determine the unit’s adjusted
performance.
Ambient Limitations
Trane air-cooled Series R
™
chillers are
designed for year-round applications
over a range of ambients. Chillers from
70-125 tons offer operation for ambients
from 25 to 115°F as standard, and will
operate down to -10°F with the low
ambient option.
The minimum ambient temperatures are
based on still conditions (winds not
exceeding five mph). Greater wind
velocities will result in a drop in head
pressure, therefore increasing the
minimum starting and operating
ambient temperature. Once again, the
Adaptive Control
™
microprocessor will
attempt to keep the chiller on-line when
high or low ambient conditions exist,
making every effort to avoid nuisance
trip-outs and provide the maximum
allowable tonnage.
Waterflow Limits
The minimum waterflow rates are given
in Table G-1. Evaporator flow rates
below the tabulated values will result in
laminar flow causing freeze-up
problems, scaling, stratification and poor
control.
The maximum evaporator waterflow
rate is also given in the general data
section. Flow rates exceeding those
listed may result in excessive tube and
baffle erosion.
The evaporator can withstand up to 50
percent water flow reduction as long as
this flow is equal or above the minimum
gpm requirements.
Variable Evaporator Flow
Air-cooled Series R
™
chillers have the
capability to handle variable evaporator
flow without losing leaving water
temperature control. Flow rates can be
varied up to 10% of design without
decreasing the leaving water
temperature control capabilities.
Temperature Limits
1. Leaving Water Temperature Range
Trane air-cooled Series R
™
chillers have
three distinct leaving water categories:
standard, low temperature, and ice
making.
The standard leaving water temperature
range is 40 to 65°F. Low temperature
machines produce leaving water
temperatures between 0°F and 39°F.
Since water supply temperature
setpoints from 0 to 39°F result in suction
temperatures at or below the freezing
point of water, a glycol solution is
required for all low temperature
machines. Ice making machines have a
leaving water temperature range of 20 to
65°F. Ice making controls include dual
setpoint controls and safeties for ice
making and standard cooling
capabilities. Consult your local Trane
sales engineer for applications or
selections involving low temperature or
ice making machines.
The maximum water temperature that
can be circulated through an evaporator
when the unit is not operating is 108°F.
The evaporator becomes thermal stress
limited at this temperature.
2. Supply Water Temperature Drop
The performance data for the Trane air-
cooled Series R
™
chiller is based on a
chilled water temperature drop of 10°F.
Temperature drops outside this range
will result in unit performance that
differs from that cataloged. For
performance data outside the 10°F
range, see Table F-1 for adjustment
factors. Chilled water temperature drops
from 6 to 18°F may be used as long as
minimum and maximum water
temperature and minimum and
maximum flow rates are not violated.
Temperature drops outside 6 to 18°F are
beyond the optimum range for control
and may adversely affect the
microcomputer’s ability to maintain an
acceptable supply water temperature
range.
Further, temperature drops of less than
6°F may result in inadequate refrigerant
superheat. Sufficient superheat is always
a primary concern in any direct
expansion refrigerant system and is
especially important in a package chiller
where the evaporator is closely coupled
to the compressor. When temperature
drops are less than 6°F, an evaporator
runaround loop may be required.