working in aeration ponds

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piroguepost

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norco, louisiana, usa
From time to time it is necessary to maintain one of 10 aerators(15-20hp 3phase 480vac) in industrial plant. The task at hand is
to use an aluminum flat boat with 12vdc trolling motor to reach the aerator and then disconnect the electrical motor. The layout
is best described as two aerators connected together about 20 feet apart with mooring cables tied to anchors on shore. There
are five sets of such arrangement. The supply cable (480vac) is laying on the ground of the pond which has stumps in it and the
level of the pond changes from time to time? Water is pumped out of the pond when necessary.
Question: there seems to be a different in opinion as to whether all the aerators should be locked out while working in the pond..
Part of the task at hand is to remove an aerator by towing it back to shore which involves crossing mooring cables and power cables.

Another question is whether or not the supply cables should be tied to mooring cables and identified as to high voltage and should
all mooring cables be bonded.
 
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GoldDigger

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piroguepost said:
From time to time it is necessary to maintain one of 10 aerators(15-20hp 3phase 480vac) in industrial plant. The task at hand is
to use an aluminum flat boat with 12vdc trolling motor to reach the aerator and then disconnect the electrical motor. The layout
is best described as two aerators connected together about 20 feet apart with mooring cables tied to anchors on shore. There
are five sets of such arrangement. The supply cable (480vac) is laying on the ground of the pond which has stumps in it and the
level of the pond changes from time to time… Water is pumped out of the pond when necessary.
Question: there seems to be a different in opinion as to whether all the aerators should be locked out while working in the pond..
Part of the task at hand is to remove an aerator by towing it back to shore which involves crossing mooring cables and power cables.

Another question is whether or not the supply cables should be tied to mooring cables and identified as to high voltage and should
all mooring cables be bonded.
Click to expand...

Is there a neutral in the 480? Is the 480 ungrounded with ground detection? (possibly the safest way to supply this equipment?)
I assume that there is a reliable EGC to the aerator housing. This means that if the water gets energized (from any one of the other still powered wiring) you will be connected very well to the water by the aluminum boat and will carry current if you touch a grounded part of the aerator or mooring cables.

I would be reluctant to work on one aerator pair or even enter the pond while the others are powered, but a lot would depend on the other details of the safety equipment.
Using a rubber or fiberglass boat, like using a fiberglass ladder, would make me more comfortable but not complacent. There had better be ground fault detection on the aerator feeds if people are likely to enter the pond routinely while they are energized.
 
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