The Tarheel Pipeline, Spring 2016

Spring 2016

NCRWA.COM

feature

electrician before purchasing a generator. A

qualified electrician who is familiar with

local building codes should also make

the connection from the generator to the

electrical distribution system. One of the

most common mistakes made in obtaining

a generator is that the unit is under-sized.

The misunderstanding often is that it can be

smaller because a back-up generator will not

be running all the time. A generator that is

too small risks damaging the unit, but it can

also create hazardous situations. The low

power output can easily damage electrical

equipment that the generator is supplying

power for. That limits the ability to operate

the facility at the levels needed. The key thing

to remember when purchasing a generator is

“more is better than less”. It is essential to

always review the power needs so that the

correct size of generator is obtained. Make a

list of all items that will need to be powered

by the generator. Correctly sizing the

generator requires the operator’s knowledge

of the equipment operated at the water or

wastewater facility. It will be necessary to

determine the voltage requirements of the

facility where power is to be supplied. Some

generators will have switches that allow

the generator to supply different voltages.

Voltage and amperage information can be

found on the data plates of the equipment

to be operated. The amperage draw on each

piece of equipment must be known. This

is important because generators operating

continuously at thirty to forty percent less

than the rated load can lead to engine damage.

Generators can be sized best if it can be a

direct match with the transformer provide by

the power company. Due to lack of power

company transformer service information,

it may be necessary to determine the KW

size of the generator needed by summing

the horsepower or amperage requirements

of all plant equipment that would be used.

Since some equipment may not be efficiently

designed, it would be prudent to add twenty

percent additional power to account for

power adjustment factors. For a temporary

installation a good rule to go by is to size

a generator from 1.5 to 2.0 times the total

horsepower requirements.

There are additional considerations in

selecting a generator. What should the fuel

type be? Gasoline, diesel, propane and

natural gas are the most popular types. Select

a fuel type that will be readily available for

your generator. If it is determined that a

portable generator will best suit the utility,

make sure that the proper conductor for your

generator size is used. The conductor must

be sized to carry the current required by the

installation. And always seek the assistance

of a qualified electrician.

SAFETY

The National Electric Code requires that

a connected generator be isolated from

utility power. That requirement is intended

to protect the generator installer from

unanticipated line power and the electrical

utility workers from power that might be

fed back into the electrical utility by a

generator. Main disconnect breakers should

never be used to isolate power sources. They

are not designed for that purpose and can

malfunction. A stationary generator must

utilize a transfer switch. If using a portable

generator and there is no transfer switch, the

line power must be disconnected at the main

breaker to ensure isolation. If the line power

is OFF because of damage to the power

company transmission lines, the generator

installer must always assume that power is

live. A generator from down the street may

be back feeding to other locations or the

power company may become active while

the installer is connecting the generator. It

is advisable by many sources to remove

the electrical meter prior to making any

generator connection for this reason. Always

practice proper lock-out, tag-out procedures

on all connections regardless whether they

are live or not.

Obtaining a generator that will meet all

the power needs is one of the most critical

steps when purchasing a generator. Whether

considering a portable or stationary unit,

the generator has to match the power

requirements. Determining the exact size

of the generator to acquire is often difficult;

this requires a number of considerations

and factors. First, is it going to be a single-

phase or three-phase unit? Most water and

wastewater facilities generally require three-

phase power. Always check with a qualified

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