| Applications 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 .00025. 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, Tables P-1 through P-19, 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 15 to 115 F as
standard, and will operate down to -10 F with the low ambient option. The larger chillers, 130-215 tons, ambient ranges from 15
to 115 F as standard, and will operate down to O F with
low ambient fans. The 240-400 ambient ranges from
0-115 F as standard. For operation outside of these ranges contact the local
Trane sales office.
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
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 Tables G-1, G-2 and G-3. Evaporator
flow rates below the tabulated values will result in
Iaminar 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 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.
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 O F
and 39 F. Since water supply temperature setpoints from O 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. |
