We've all heard the stories; a roof top air conditioner bogs down and trips the breaker;
a television set image is suddenly reduced to a much smaller viewing area; your neighbor
plugs his coach into the campground and your microwave oven quits in mid-cycle; reports of
a lightning storm in the next county are followed by the lights inside your coach all of
a sudden become very, very bright. I could go on, but I think most of you get the idea.
The fact is, there are a myriad of electrical problems equally available to all RVers in
virtually every corner of North America at any given time in any season. Collectively known
as "power line problems," individually they create a palette of dilemmas that we must be
aware of and hopefully protect against. Why? Quantum leaps in RV electrical technology over
the years has resulted in many components in our coaches now being controlled by electronic
boards and microprocessors. Additionally, the computer explosion and e-mail form of communications
have well-permeated the general RVing public. Fax/modem applications, CATV (cable TV),
connections and on-board telephone connections are becoming quite common. There exists
many "smart" devices controlling everything from RV washing machines and battery chargers
to VCRs and microwave ovens. Face it, we are firmly entrenched in the microprocessor and
electronic age of RVing. Now with the push of a single button you can even deploy a full-length
patio awning, or extend a room addition, all using electronically controlled circuitry. Power
line problems are no longer just a concern for the computer industry.
The AC power line, manifested at that campground pedestal or the AC receptacle you plug into
while at your home base, is the tethered life blood for all things AC and many items DC in the
RV. But it can also be the pathway for a mystifying menace that can render useless many components
found in the coach. Let's take a detailed look at some of these power line enigmas and how to
protect our hi-tech recreational investment from potential disaster.
Oftentimes we read in an article or hear in an electrical seminar, terms such as spike, sag,
dip, surge, etc., with precious little in the way of full definition. To truly understand
alternating current power problems, familiarize yourself with the following definitions.
Steady-State Voltage: normal voltage planned for a system that stays constant for ten seconds
or longer. RV applications require 120-VAC at a frequency of 60-Hz, usually providing 30 amps
of service for most RVs. 50-amp service simply includes another leg, or phase, of 120-VAC also
at 60-Hz. (Hertz or Hz, is the unit of electromagnetic frequency for the change in cycle in
alternating current. Hertz replaces the older term of "cycles per second," or cps).
Power Failure: a zero voltage condition lasting for more than one cycle (1/60 of a second).
From a power grid standpoint, it could happen on any of the three phases being delivered.
Dropout: a portion of the sine wave that has a lower value or is missing altogether, but only
for a small portion of any given cycle.
Blackout: a total power failure lasting several seconds to many hours.
Brownout: a planned and usually announced region-wide reduction of available steady-state voltage.
Typically associated with an impending expectation for heavy electrical consumption.
Sag: a cycle-to-cycle reduction of power line voltage of at least 10% of the average voltage
for half of one cycle or longer. A sag might occur when your RVing neighbor first turns on his roof top
air conditioner. Sags are detrimental to electronically controlled devices such as microwave
ovens, television sets and VCRs.
Dip: a faster sag. Dips are short decreases in the nominal line voltage, but are much quicker
than a sag. Usually only visible in an incandescent light bulb.
Notch: similar to a dropout though typically too fast to see. They can be up to several
milliseconds in duration and usually come in pairs. For every notch there is usually an
immediate spike following behind. A notch is simply an out-of-phase impulse, (see impulse below).
Surge: the opposite of a sag, surges are cycle-to-cycle increases in the voltage on any of
the three phases above the normal voltage but typically below 500 total volts. The lasting time of
a surge is equal to its duration for the number of 60-Hz cycles that the power line disturbance is
above normal.
Swell: basically a series of long term surges that lasts form a few seconds to several minutes.
Impulse: a very short disturbance of either polarity, (up or down), superimposed on the
AC sine wave that lasts between .5 and 100 microseconds. In-phase impulses which instantaneously
increase the voltage are called spikes. Out-of-phase impulses which decrease the voltage are notches.
Spike: an in-phase, over-voltage impulse ranging from 400 volts to well over 5,600 volts! Such
an impulse is superimposed on top of the AC sine wave and typically lasts for less than 1/000 of
a second, (one millisecond). Any spike over 600-volts can be very damaging. Spikes contain high
amounts of energy and are most detrimental to sensitive circuitry.
Transient: any short-term power disturbance on the power line. All the above disturbances
are transient by definition. Transients can either be oscillatory, varying consistently with
the frequency, or they can be of the impulse variety.
Oscillatory transients are usually caused by;
Lightning strikes - the most common cause of spikes and surges. Lightning is most common
and most severe during the summer months, though lightning has been observed during snow storms!
Lightning strikes can render sophisticated electronics in the RV useless or operationally
intermittent. In either case, costly. Surprisingly, lightning does not need to strike nearby
to reap havoc. A storm miles away could induce spikes that can ultimately reach your campsite
pedestal. Lightning between clouds, never directly striking power lines or phone lines, will
create large magnetic fields that can also cause surges and spikes in your equipment.
Utility grid switching - your friendly power utility company can be responsible for creating
spikes and surges simply by switching high power distribution lines. Power lines can also pick
up transients from power company operating equipment.
Campground pedestal hook-ups - even the power pedestal located in your favorite campground
can be the source of transients. Many RV campgrounds and destinations sites were constructed
some time ago when demand for current was not as prevalent as today. RVs of yesteryear rarely
used a full 30 amps of current draw and 50-amp service was unheard of. With today's larger RVs
demanding more power to operate the modern conveniences we have come to expect, many older
campgrounds are simply electrically undersized and outdated. When demand is high for current
in an overloaded campground, the power sags or dips drastically. Power line transformers on
the grid compensate when low voltage is sensed by raising the voltage. When the demand for
power sufficiently loads that transformer, all is well, but when the load is slight, the
voltage could remain at dangerously high levels.
Impulse transients are usually caused by;
Faulty wiring, (loose connections) - common in campground connections and from within your own RV.
Motor load switching
Improper grounding or bonding of power lines
According to some electrical industry studies, voltage transients represent 12 to 15% of all AC
power line problems with only about 35% of those problems originating from outside on the utility
grid. As many readers have personally experienced, and as mentioned above, problems can originate
from within the campground itself or from within our very own recreation vehicle. In the campground
or at a home base, transients can occur simply from a ground voltage differential between improperly
bonded grounds during electrical faults. It is important to understand that given the state of
the art of the technology we now employ in RV configurations, all AC power lines, campground phone,
cable TV and data communication lines must all be commonly grounded or bonded together to prevent
transients voltages from entering sensitive equipment.
One study shows that surges and impulse spikes can occur as frequently as twice per hour in any
typical residence; some with peak values at 1,500 to 2,500 volts. In industrial applications,
such as in a large campground, they can be more frequent and more severe with spikes as high as
5,600 volts as recorded during lightning storms. A study by IBM in various locations across the
United States revealed an average of 50.7 voltage spikes per month. Another study showed that
many locales will experience approximately twenty-five power line disturbances per year, 87% of
which will probably be sags below 96-VAC. Voltages below 105-VAC can be very damaging to induction
loads found in RVs such as the roof top air conditioner.
The bottom line is that electrical disturbances, the so-called "power line problems" are severe,
they occur often and the damage can be substantial, which usually equates to expensive. What goes
mostly unnoticed is the accumulative effect on sensitive equipment in the RV after enduring spikes,
surges, dips, notches, etc. The long term performance deterioration of some delicate components
may not surface until later, all the while the equipment performs at a sub-standard level until
failure occurs.
So what can be done? One of the best solutions is to have a full-time spike suppressor/surge
protector in your RV. A number of suppliers now provide such protective devices for the RV
industry. Technology Research Corporation, a long-time provider of transient voltage protection
devices to other industries including the military, was the first company to offer RV specific
equipment protection. RV Electronics also produces a similar protection device specifically
for the RVer.
Surge protectors act like an electrical sponge of sorts, absorbing excess voltage, thereby
protecting your RV. RV surge protection should include the ability to completely shut off
the incoming power before damaging transients can reach sensitive equipment. Additionally,
they should have the capability to monitor and detect high voltage and low voltage conditions
and to interrupt the incoming power until the system has returned to safe levels over a period
of time.
Most surge protectors utilize MOVs, (Metal Oxide Varistors) to protect against transients voltages.
The quality devices usually have a minimum of three MOVs in the circuitry. More sophisticated
protectors, such that might be used on a computer system inside your RV have what is called
sine wave tracking which actually tracks the incoming AC signal and literally cuts off the
top portion of the wave. It provides better protection for highly sensitive, usually expensive
equipment. The key to this technology is determined by the "clamping voltage rating" also
called the "let-through voltage rating." The lower the rating, the better the protection.
Sine wave tracking protectors have a remarkably tight clamping voltage surrounding the incoming
power line sine wave.
Many companies extol the Joule Rating of their surge protection device. A "joule" is a measurement
of energy that indicates the amount of energy that a device is capable of absorbing. The joule
rating is primarily determined by the total number of MOVs in the device. Unfortunately, there
is no standard for measuring the joule rating of surge suppressors, but generally those with a
higher rating are considered better. It is felt by many in the surge protection business that
the joule rating of a surge suppressor is less important than the "let-through voltage" rating.
Underwriters Laboratories, (UL), has, however, developed a minimum standard for spike suppressors.
The surge protector you choose to install in your RV should meet or exceed the requirements of
UL 1449.
You are encouraged to investigate the feasibility of adding transient voltage protection to your
electrical system. If you truly value the electrical equipment in your RV and are well aware of
the consequences, it can be considered cheap insurance at the very least.
