Fluke all products Application Note

Monitoring power usage:

ve reasons to log power

and energy use

Application Note

1. Safety

Electricians are often required
to conduct a load study before
adding a new electrical load
to an existing panel or service.
Why? The requirements come
from the electrical Inspector, the
electrical engineer who designed
the project, or the customer
adding the new load and the
reason is to determine if there
is sufficient capacity to add new
loads. A load study involves using
a logger to document existing
load levels (three phase current
draw) over time. That’s where
safety comes in. On the positive
side, a load study can be used to
ensure adherence to local safety
regulations. On the negative side,
failure to perform a load study
before adding new loads can
result in overloading an existing
electrical source, creating electri­cal safety and reliability hazards.

2. Manage energy costs and
realize savings opportunities

While energy expenditures are
a significant portion of overall
operational cost, many companies
don’t really know where their
energy dollars are being spent,
since all they get is one overall
monthly bill, with no indication
of whether that use was standard
or excessive compared to opera­tions that month. By logging
power use at the main service
entrance and then at large loads
and secondary supplies, facili­ties can see how much power is

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being used when, by what, and
at what hourly cost. Without fail,
the data will turn up several
energy wastes that can be
rectified by operational changes
alone, such as turning off certain
loads, reducing loads during peak
rate periods, or adjusting the
schedule so that loads operate
during non-peak rate periods.

3. Accuracy of electrical bill

Owners of large and medium
sized facilities often install elec­trical sub metering to bill tenants
for their specific electricity usage.
However, these sub meters are
commonly installed improperly,
putting that billing into ques­tion. Installation issues vary, from
current transducers installed
backwards, current transducers
on the wrong phase, and errors
in configuring the sub meter.
A good business practice is to
double check the reading with a
portable energy logger. Logger
data provides a rough order of

2 Fluke Corporation Monitoring power usage: five reasons to log power and energy use

magnitude comparison of what is
being billed versus what is actu­ally used. A significant deviation
between the amount charged for
electricity usage and the logger
data would signal the need to
investigate the sub meter setup.

4. Rebates and financial
incentives

Utility companies offer incentives
and rebates as a way to encour­age their customers to decrease
energy use. The goal is to serve
more customers with the same
existing power supply, since
building new power generation
plants is prohibitive. Many
incentives and rebates are
available for retrofitting existing
buildings, such as energy effi­cient lighting and high efficiency
motors, as well as replacing
motor starters with variable
frequency drives. In order to
receive the financial incentive,
the utility company will often
require verification of the energy

savings—an ideal scenario for a
load study. A pre-retrofit load
study will document the existing
energy use to provide baseline
data, while a post-retrofit load
study verifies the energy savings
achieved upon completion of the
modifications.

5. Troubleshooting

There are many times when the
only way to troubleshoot a prob­lem is to capture and analyze
data over an extended period
of time. For these advanced
troubleshooting scenarios, energy
loggers are invaluable—and
they are much more afford­able and easier to use than a
more complex power analyzer. A
good example is when a circuit
breaker trips randomly. Obvious
events, like a large motor start­ing up, may not be the cause. In
fact, what causes the trips might
appear to be totally random or
may occur when technicians are
not around to observe it (like the
middle of the night). Because it’s
impractical for a maintenance
technician to monitor the load
until the circuit breaker trips,
connecting an energy logger
to the load side of the circuit
breaker to record the current
draw over time can help trouble­shoot the trip.

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©2013 Fluke Corporation.
Specifications subject to change without notice.
Printed in U.S.A. 8/2013 6000862A_EN

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without written permission from Fluke Corporation.