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balance the makeup water with tower operation. Ideally, the oat valve
setting will be such that no water is wasted through the overow at
pump shutdown. However, the water level after pump start-up must
be deep enough to assure positive pump suction.
5. If a multicell tower installation is equipped with ow-control valves,
adjust them to equalize hot water depth in the distribution basins after
reaching design water ow rate. Each basin should have from 2
3
⁄4" to
5
1
⁄2" (70 mm to 140 mm) water depth, with uniform depth from basin
to basin. Fix valves in this position when depth is correct. If the tower
is a single cell installation this step is not necessary.
Uniform distribution depth of 2
3
⁄4" to 5
1
⁄2"(70 mm to 140 mm) is essential
to efcient tower operation. Contact your Marley sales representative
if you are considering a permanent change in circulating water ow
rate that would prevent operation within these limits.
6. Continue pump operation for about 15 minutes, after which it is rec-
ommended that the water system be drained, ushed, and relled.
7. While operating the condensing water pump(s) and prior to operat-
ing the cooling tower fan, execute one of the two alternative biocidal
treatment programs described in the following:
• Resume treatment with the biocide which had been used prior
to shutdown. Utilize the services of the water treatment supplier.
Maintain the maximum recommended biocide residual (for the
specic biocide) for a sufcient period of time (residual and time
will vary with the biocide) to bring the system under good biological
control
or
• Treat the system with sodium hypochlorite to a level of 4 to 5 mg/L
(ppm) free chlorine residual at a pH of 7.0 to 7.6. The chlorine re-
sidual must be held at 4 to 5 mg/L (ppm) for six hours, measurable
with standard commercial water test kits.
If the cooling tower has been in operation and then shut down for a
duration of time and not drained, perform one of the two previous
biocidal treatment programs directly to the cooling water storage
vessel (cooling tower sump, drain down tank, etc.) without circulating
stagnant water over the cooling tower ll or operating the cooling tower
fan. After biocidal pretreatment has been successfully completed,
cooling water may be circulated over the tower ll with the fan off.
Operation
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