Carrier 16DF013-050 - Manual (Page 53)

Condensing Water Tube Scale is indicated if the tem-
perature difference between condensing water leaving the con-
denser and refrigerant condensate from the condenser is greater
than the normal 4 to 7° F (2 to 4° C) difference at full load
(capacity control valve fully open). Scale reduces heat trans-
fer, increases steam consumption, and limits machine capac-
ity. Scale can also cause serious corrosion damage to the tubes.
Soft scale can be removed from tubes with cleaning brushes
specially designed to avoid scraping or scratching the tube
walls. The brushes are available through your Carrier rep-
resentative. Do not use wire brushes.
Hard scale may require chemical treatment for its pre-
vention or removal. Consult a water treatment specialist
for proper treatment.
Water Treatment — Untreated or improperly treated wa-
ter may result in corrosion, scaling, erosion, or algae. The
services of a qualified water treatment specialist should be
obtained to develop and monitor a treatment program.
Water must be within design flow limits, clean, and treated
to ensure proper machine performance and reduce the
potential of tubing damage due to corrosion, scaling, or
erosion. Carrier assumes no responsibility for chiller dam-
age resulting from untreated or improperly treated
water.
Solution Decrystallization — Crystallization occurs
when strong solution concentration and temperature cross
over to the right of the crystallization line on the equilibrium
diagram (Fig. 30A and B). It should not occur if machine
controls are correctly adjusted and machine is properly op-
erated. Refer to the Troubleshooting Guide, pages 54 - 56
for probable causes and remedies.
If crystallization occurs, it generally takes place in the shell
side of the low-temperature heat exchanger and blocks the
flow of strong solution from the low-stage generator. The
strong solution then overflows into a pipe that returns it di-
rectly to the absorber sump. The solution pump then returns
the hot solution through the heat exchanger tubes, automati-
cally heating and decrystallizing the shell side.
However, if the cause of the crystallization continues, the
solution crystallization can continue and may become se-
vere. In that case, depress the chiller/heater Stop button, place
the burner control at MANUAL, and depress the machine
Start button for restart. Place the dilution valve on manual to
dilute the solution and open the heat exchanger bypass valve
‘‘C’’ to help solution circulation. When the solution has been
completely decrystallized, reset the switches to the normal
positions and close valve ‘‘C’’.
If crystallization results from a long, unscheduled shut-
down (such as from a power failure) without proper dilu-
tion, the solution pump(s) may become bound and fail to
rotate. This will cause the overloads to trip out. In such a
case, decrystallize as follows:
1. Heat the solution pump casing and adjacent lines with
steam.
Under no circumstances apply heat directly to pump
motor or controls when warming the casing. Do not
apply direct heat to any flange connections; high tem-
perature can deteriorate the gasket material.
2. Rotation of a hermetic pump cannot be viewed directly.
Check the solution pump rotation by installing a com-
pound gage on the pump service valve and reading dis-
charge pressure. Be sure to reset the pump overloads in
control panel if they are tripped.
If the pump is rotating normally, the gage will show a
reading above atmospheric pressure. If the pump casing
and discharge line are completely blocked, the gage will
show zero atmospheric pressure. If the pump interior is
only partially blocked, a deep vacuum will indicate that
the pump is not rotating.
3. Continue heating the casing until gage pressure shows above
atmospheric pressure with pump overloads reset. Do not
reset pump overloads more than once in any 7-minute
period.
If the heat exchanger is also blocked, the decrystalliza-
tion process will begin as soon as the solution pump starts
rotating and the adjacent weak solution lines have de-
crystallized. If the heat exchanger or adjacent piping does
not decrystallize automatically, heat the blocked area ex-
ternally with steam or a soft torch flame. Crystallization
in purge piping can be broken up by applying heat in the
same manner.
4. If the strong solution line from heat exchanger to ab-
sorber spray nozzles is blocked, turn off the condensing
water pump and operate the machine with the burner op-
erating on MANUAL. Turn the dilution switch to MANUAL
to dilute the solution. The entire unit will pick up heat
and the crystallization will dissolve. If severe crystalli-
zation is present, it may take 4 to 6 hours to fully de-
crystallize, but the burner should be left on only long enough
to heat the solution.
Internal Service — To prevent corrosion from air in-
side the machine, break vacuum with nitrogen when open-
ing the machine for maintenance or repair.
While the machine is open, it is good practice to mini-
mize the amount of air entering by continuously feeding
nitrogen into the machine at approximately 1 psig (0.1
KgF/cm
2 G) pressure.
Perform service work promptly and efficiently and close
up the machine as soon as possible. Do not rely on inhibitor
for corrosion protection from exposure to air.
Leak test the machine thoroughly after the machine has
been closed up.
When flamecutting or welding on an absorption ma-
chine, some noxious fumes may be produced. Ventilate
the area thoroughly to avoid breathing concentrated fumes.
Hydrogen can form an explosive mixture in air. Never
cut into purge chamber unless purge has been ex-
hausted to remove any hydrogen gas that might be present
in the chamber.
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