| Application Considerations
Figure A-4 — Typical
Condenser/Absorber Cooling Water Piping with Cooling Tower
Figure A-5 — Typical
Condenser/Absorber Cooling Water Piping with Well or River Water
Well or River Water
1. Balancing Valve
2. Gate Valve
3. Thermometer (Optional)
4. Pressure Gauge, Vent and Shut-off
Valves
5. Union or Flange Connection
6. Pipe Stub
7. Stainer
8. Pump
9. Flow Switch
Cooling Water Piping
The cooling water piping design for absorption chillers
differs from conventional reciprocating and centrifugal systems in that cooling water
passes through the absorber section of the machine prior to entering the condenser. The
cooling water flow must be controlled by the absorption machine as a function of normal
control and machine safety.
Trane absorption machines are designed to startup with
cooling tower water temperatures as low as 45 F (+7.2 C) and operate with temperatures as
low as 55 F (+12.8 C). In typical applications, the machine is selected on the basis of
the cooling water temperature available at full load. This is usually 85 F (+29.4 C).
With the cooling tower sized for design conditions, the
temperature of the cooling water supplied to the unit will decrease with any decrease in
cooling load or depression of outside wet bulb temperature. These reduced cooling water
temperatures will normally tend to increase the capacity potential of the absorption
machine. The Trane control system takes advantage of this improved efficiency by using
automatic controls that limit the energy input to the machine based on entering cooling
water temperature. This also helps prevent overheating.
Cooling water temperature control is always required. At
light loads with cold outside conditions, cycling of the cooling tower fan will result in
undesirable variation in steam demand and leaving chilled water temperature. Consequently,
Trane recommends consideration of multiple speed tower fans or a cooling tower bypass
valve to reach equilibrium at all load conditions. Rate of change allowable is 1 degree
per minute.
Figure A-4 and A-5 illustrate the recommended methods to
apply cooling water to the Trane Absorption machine. In those cases where a cooling tower
bypass is not used, multiple cooling tower fans are recommended.
Water temperature sensors are factory-installed on the
entering and leaving sides of the absorber and condenser water connections. The operating
temperatures can be monitored from the control panel.
Water Treatment
The use of untreated or improperly treated water may result
in scaling, erosion, corrosion, algae or slime. It is recommended that the services of a
qualified water treatment specialist be used to determine what treatment, if any, is
advisable. The Trane Company assumes no responsibility for the results of untreated, or
improperly treated water.
Cooling Tower Water Flow
The ARI standard gpm/ton for steam absorption chillers is
4.0 but lower flow through the condenser and absorber section will present an opportunity
for a smaller tower and smaller condenser pump or piping. Trane two-stage absorption
chillers were designed around 3.6 gpm/ton. By designing a system around lower flows there
will be significant annual chiller plant electrical energy savings and lower initial
equipment costs. For more information on lower flows on the cooling tower water circuit
refer to the appropriate engineering bulletin.
Electric Service
Factory wired and mounted power control includes main power
connections. Units may be supplied for operation on 230, 460 or 575 volt, 3 phase, 60
hertz power. Also 190, 220, 380, 415 volt, 3 phase, 50 hertz power is available.
Machine Installation
A housekeeping pad or support rail is recommended to
elevate the machine for maintenance. Any foundation pad should provide adequate structural
support and keep the installed machine level within 1 /16 -inch by length and width for
reliable operation. Leveling marks on the tube sheet can be used to check the machine
after it is positioned on the pad.
Separated Machine Sections
Disassembled machines are available factory separated in
two or three main sections. The three piece option ships as an evaporator/absorber
section, the high temperature generator section and the low temperature
generator/condenser section. The two piece option will ship the evaporator/absorber, in
one piece and the low temperature generator/condenser/high temperature generator as a
separate piece. |
