Fluke 773 Service Guide

Electronics in your building

don’t like power problems

Lightning strikes,

power loss/generator testing,

utility problems

By Ron Auvil

In my role as a senior project technician I spend a lot of time

in buildings diagnosing problems. My responsibilities involve

electronic controls on HVAC equipment. I also try to help the

customer by diagnosing common problems with other

equipment, which might include telephone systems, elevators,

security equipment, and life safety systems.

Admittedly, while working on
problems with these various
systems I can be a little slow
to note a common denomina­tor. But over a period of time
I have noticed something that

repeats itself over and over
again—problems due to power!
Approximately 25 to 35 percent
of the service calls I get are
related somehow to a power
issue of one type or another.

Application Note

Prevalence of electronics

It does not take a genius to
recognize that almost every major
subsystem in today’s commer­cial buildings has some type of
solid-state electronics package
installed. Virtually every HVAC
unit purchased today has an
electronics board in the control
panel. Ditto for security, fire,
and life-safety systems. Digital
telephone and computer network
systems are the same. Regard­less of system type, the common
element is the electronics.

Another factor in this elec­tronics equation is that there are
“old” electronics and “new” elec­tronics. Some electronic systems
in today’s building equipment
were installed 20 or more years
ago, and are even more suscep­tible to problems.

All of the electronic systems
mentioned above can have
problems due to power. Many
electronics and device manu­facturers will claim an amount
of tolerance to power problems.
Many will say that a fault due
to power “should not” happen.
Unfortunately the nice tech
support folks on the other end
of the telephone are not stuck
on an elevator or listening to
the fire alarms going off after a
thunderstorm.

Typical power scenarios

Anyone working in a field utiliz­ing electronics in a building
should be able to easily recog­nize the scenarios that affect the
power to the electronics. These
scenarios typically are very

A communications card can be easily damaged by incoming power problems. Burn marks
on the electronics and a burning smell are indicators.

From the Fluke Digital Library @ www.fluke.com/library

repetitive in the building and in
some cases occur frequently.

Lightning strike

One of the most common sce­narios is a lightning strike. The
prevalence of this problem will
depend greatly on your location
and climate. I happen to live in
the southeastern United States,
which is famous for summer
thunderstorms in the afternoon.

My personal rule of thumb is
that after a thunderstorm moves
through I will get at least one
or two calls from a building that
are lightning-related. Sometimes
I can even watch weather radar
and know exactly which of my
buildings will be calling me.

Lightning can cause a whole
host of problems. Keep in mind
that a lot of the electronics,
especially HVAC equipment, are
located on the roof or outside
the building. This makes it even
more susceptible to lightning. If
lightning is the culprit, its effects
can be catastrophic. In many
cases the electronics are wiped
out, with visible burn marks and
a burned smell.

Moving the electronics, as
well as better lightning protec­tion and grounding, can help.

If a computer program is
running on an electronic chip
in the device (EEPROM or Flash
ROM) it may be wiped clean by
the lightning strike and start
up “stupid”—not operate at all. I
have a building with old 1990s
electronics that have to be
reprogrammed after every major
thunderstorm. It is not uncom­mon, after a power problem, that
1 to 5 percent of the devices on
a building automation system
network do not communicate or
function properly.

Recently I received a call that
the fireman’s panel in a build­ing was not functioning. This
building has suffered from many
power problems in the recent
past, usually one every two
weeks or so. The electronic con­troller in the panel had faulted
out and had to be replaced.
Obviously this was a critical
system. The electronic controller
was replaced and started up. It
worked for a few seconds and
then rebooted every 10 seconds.

An iFlex™ flexible cur rent probe is wrapped around the motor leads
at a variable speed drive so the c urrent can be measured with the
Fluke 381 Clamp Meter. This shows whether or not a variable speed
drive has been damaged by a lightning strike.

The incoming power was turning
on and off every 10 seconds.
I could hear a clicking noise
and traced it to an uninterrupt

­ible power supply (UPS) in the
ceiling. The continuous power
problems had damaged the UPS
and caused it to cycle on and off.
If left as-is, the life safety panel
would not function properly
and the new controller would
be damaged. We had to replace
the damaged UPS as well. The
fireman’s panel then functioned
properly.

Power loss/generator
testing

Another problem is power loss.
There can be many causes of a
power loss, including utility prob
lems, maintenance lapses, device
surges, and others. Depending
on the condition that caused it,
an electronic device may not
recover properly after the power
is restored.

When a power loss occurs, the
backup generator will start after
a short time delay. I happen to
work in hospitals a lot, and by
code the backup generators have
to start within 10 seconds after
utility power loss. Also by code
the backup generators are tested

-

You can check the controller power supply voltage with a Flu ke 773
Milliamp Process Clamp Meter. Power problems can affec t the power
supply and cause the controller to ma lfunction or fail.

once per month. Important build­ing electronic devices are on this
backup power circuit. Depend­ing on the causes, there may be
power surges as well as voltage
and current problems as the

2 Fluke Corporation Electronics in your building don’t like power problems