14
Some trial and error adjustment of the float valve may be required to balance
the makeup water with tower operation. Ideally, the float valve setting will
be such that no water is wasted through the overflow at pump shutdown.
However, the water level after pump start-up must be deep enough to
assure positive pump suction.
5. If the tower is equipped with flow-control valves, adjust them to
equalize hot water depth in the distribution basins after reach-
ing design water flow rate. Each basin should have from 3" to 5
1
⁄
2
"
water depth, with uniform depth from basin to basin. Fix valves in this
position with the locking bar when depth is correct. Failure to tighten the
locking bar after valve adjustment may result in damage to the valve. If the
tower is equipped with the Marley internal piping option, the basins are
self-balancing and this step is not necessary.
Uniform distribution depth of 3" to 5
1
⁄
2
" is essential to efficient tower op-
eration. Contact your Marley sales representative if you are considering a
permanent change in circulating water flow rate that would prevent operation
within these limits.
6. Continue pump operation for about 15 minutes, after which it is recom-
mended that the water system be drained, flushed, and refilled.
7. While operating the condensing water pump(s) and prior to operating 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 shut-
down. Utilize the services of the water treatment supplier. Maintain the
maximum recommended biocide residual (for the specific biocide) for
a sufficient 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 ppm free
chlorine residual at a pH of 7.0 to 7.6. The chlorine residual must be
held at 4 to 5 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 fill or operating the cooling tower fan.
installation