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ABS-PRC001-EN
Job Site
Connections
Steam Supply and
Condensate Piping
Condensate Handling
Figure JC-1 illustrates a typical
condensate system consisting of steam
traps, condensate receivers and
condensate pumps. Such systems
provide the most economical method for
returning condensate to a boiler.
Properly-sized float and thermostatic
traps are required for proper operation.
The use of bucket traps is not
recommended.
Trane absorption machines use steam-
throttling control. A maximum of three
percent of the condensate may flash to a
vented receiver at full load. This flashing
decreases as the load decreases, and is
virtually nonexistent below 70 percent
load. When the machine is operating at
less than 70 percent load, the pressure in
the generator tube bundle may be below
atmospheric pressure. The temperature
of the condensate leaving the machine
under these conditions is less than 212°F
[100°C], so flashing does not occur.
A subcooler may be installed ahead of
the receiver to cool the condensate to a
temperature below the saturation
temperature at atmospheric pressure,
thus eliminating flashing entirely. It is
recommended that a cooling medium,
such as boiler feed water, be used to
keep this energy within the system. The
pressure drop through the subcooler
should be minimized.
Figure JC-1 indicates an equalizer line
installed to avoid condensate backup in
the machine. The swing check opens if a
vacuum develops within the tube bundle
under part-load operation.
This prevents development of a lower
pressure in the concentrator than at the
outlet of the trap.
Packaged Condensate Systems
Several manufacturers have available
packaged condensate-pump systems,
designed for various condensate
temperatures. A decision regarding the
use of these systems with a Trane
absorption machine should be based on
a thorough economic analysis of the
particular installation. The following
factors should be considered:
1. Condensate may flash in the receiver
less than 20 percent of the total
operating time in a typical installation.
The amount of condensate that may
flash varies from a maximum of three
percent at full load, to none at less
than 70 percent load. A subcooler can
be used to eliminate the small amount
of flashing that may occur when the
machine is operating under heavy
load.
2. The condensate system must prevent
condensate from backing up into the
machine at part load when the
pressure in the generator tube bundle
is below atmospheric pressure.
3. The condensate system must not
draw supply steam through the
machine. This reduces the machine
efficiency and may offset any potential
energy savings that might otherwise
be realized by the use of the
condensate return system. Also,
reduced tube life would result due to
erosion.
If the decision is made to use a packaged
condensate-pump system, follow the
manufacturer’s recommendations
regarding its application.