Carrier 69NT40-511-300 Operation And Service page 79

refrigerant vapor is admitted to the shell side and is
condensed on the outer surface of the coil.
Rust, scale and slime on the water-cooling surfaces
inside of the coil interfere with the transfer of heat,
reduce system capacity, cause higher head pressures
and increase the load on the system.
By checking the leaving water temperature and the
actual condensing temperature, it can be determined if
the condenser coil is becoming dirty. A larger than
normal difference between leaving condensing water
temperature and actual condensing temperature,
coupled with a small difference in temperature of
entering and leaving condensing water, is an indication
of a dirty condensing coil.
To find the approximate condensing temperature, with
the unit running in the cooling mode, install a gauge 0 to
36.2 kg/cm@ (0 to 500 psig) on the compressor
discharge service valve.
Example: Discharge pressure is 10.3 kg/cm@ (146.4
psig). Referring to Table 6-9 (R-134a pressure/
temperature chart), the 10.3 kg/cm@ (146.4 psig) value
converts to 43_C (110_F).
If the water-cooled condenser is dirty, it may be cleaned
and de-scaled by the following procedure:
a. Turn unit off and disconnect main power.
b. Disconnect water pressure switch tubing by loosen-
ing the two flare nuts. Install one-quarter inch flare
cap on water-cooled condenser inlet tube (replaces
tubing flare nut). De-scale tubing if necessary.
What You Will Need:
1. Oakite composition No. 22, available as a powder in
68 kg (150 lb) and 136 kg (300 lb) containers.
2. Oakite composition No. 32, available as a liquid in
cases, each containing 3.785 liters (4 U.S. gallon)
bottles and also in carboys of 52.6 kg (116 lbs) net.
3. Fresh clean water.
4. Acid proof pump and containers or bottles with rub-
ber hose.
NOTE
When Oakite compound No. 32 is being used
for the first time, the local Oakite Technical Ser-
vice representative should be called in for their
suggestions in planning the procedure. They
will advise the reader on how to do the work with
a minimum dismantling of equipment: how to
estimate the time and amount of compound
required; how to prepare the solution; how to
control and conclude the de-scaling operation
by rinsing and neutralizing equipment before
putting it back into service. Their knowledge of
metals, types of scale, water conditions and de-
scaling techniques will be highly useful .
Summary of Procedure:
a. Drain water from condenser tubing circuit. Clean
water tubes with Oakite No. 22 to remove mud and
slime.
b. Flush.
c. De-scale water tubes with Oakite No. 32 to remove
scale.
d. Flush.
e. Neutralize.
f. Flush.
g. Put unit back in service under normal load and check
head (discharge) pressure.
Detailed Procedure:
1. Drain and flush the water circuit of the condenser
coil. If scale on the tube inner surfaces is accompa-
nied by slime, a thorough cleaning is necessary
before de-scaling process can be accomplished.
2. To remove slime or mud, use Oakite composition No.
22. Mixed 170 grams (6 ounces) per 3.785 liters (1
U.S. gallon) of water. Warm this solution and circu-
late through the tubes until all slime and mud has
been removed.
3. After cleaning, flush tubes thoroughly with fresh
clean water.
4. Prepare a 15% by volume solution for de-scaling, by
diluting Oakite compound No. 32 with water. This is
accomplished by slowly adding 0.47 liter (1 U.S. pint)
of the acid (Oakite No. 32) to 2.8 liters (3 U.S. quarts)
of water.
Oakite No. 32 is an acid. Be sure that the
acid is slowly added to the water. DO NOT
PUT WATER INTO THE ACID - - this will
cause spattering and excessive heat.
Wear rubber gloves and wash the solution
from the skin immediately if accidental con-
tact occurs. Do not allow the solution to
splash onto concrete.
5. Fill the tubes with this solution by filling from the bot-
tom. See Figure 6-17. Important: be sure to provide
a vent at the top for escaping gas.
Centrifugal pump
30 GPM at 35' head
Priming
connection
Pump
Suction
Tank
Pump
support
Figure 6-17 Water-Cooled Condenser Cleaning - -
Forced Circulation
6-11
WARNING
WARNING
Vent
Close vent pipe
Globe
valve when pump
valves
is running.
Condenser
Remove water
regulating valve
Return
Fine mesh
screen
T-285