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Part 1: Are You Inspecting the
things that are REALLY Important?
Everything is important when it comes to
inspecting electrical systems. The reality is, however, that we can't
spend as much time in a house as we would like to spend. Almost every home
inspector I know would spend at least a full day in every house if they could.
The trouble is that we are not going to be making much money if we spend a full
day in the house.
We need to be sure that we inspect the
parts of the electrical system that are most likely to cause serious problems if
there is a defect or a deficiency. I cannot stress enough that I am not
saying that there are things that are not important.
I do two things when inspecting an
electrical system. First, I look for problems that already exist. My
main focus is in areas that I know are common failure points in an electrical
system. Second, just as economist judge the health of the economy by
looking at "key indicators", I look for "key indicators" that there may be
hidden defects or deficiencies.
I did thousands of service calls when I
worked as an electrician. In recent years, I have done dozens of
electrical fire investigations and hundreds of electrical inspections. I
have seen first hand experience where and how electrical systems fail.
Electrical system do not fail the ways that
people tend to think they will fail. Even experienced electricians and
electrical engineers are often surprised to learn the real facts.
Your inspection should focus on the things
that are most likely to cause a catastrophic failure. Unlike other
mechanical in a home or commercial building, when electrical systems fail the
failures usually lead to catastrophe.
Common
causes of electrical disasters
Here are some of the the most common
causes of electrical disasters*:
* Fire, explosion, and electrocution
1. Improper connections in junction boxes
(usually in attics)
Improper connections in junction boxes
cannot always be readily viewed because you would need to remove junction box
covers. There are often signs of improper work that are visible
without removing a cover. Metal electrical boxes all have a #10 threaded
hole in the back. The purpose of the hole is to secure a ground wire with
a screw. A ground wire wrapped around one of the box cover's screws is an
indication of amateur work. Ground wires should NEVER be wrapped
around a cover screw.
Amateurs often leave covers off of boxes.
I have never been able to figure out why but, they do. That's makes our
jobs as home inspectors a little easier. The fact that there is not a
cover is in itself a deficiency that needs to be corrected. The absence of
a cover also gives us an opportunity to see what is inside the box.
Amateurs usually do not know how to install
twist-on solderless electrical connectors. They tend to put electrical
tape over the connectors. In doing so, they can create dangerous
connections. Most people will wrap the tape clockwise. Solderless
connectors are also turned clockwise to install them. Electrical tape is
stretched around the connector. The tape is elastic so it is going to try
to go back to its unstretched state. In doing so it can loosen a
connection may not have been secure in the first place.
Taped connections do not all fail but the
chances of a taped connection failing are unacceptably high. Assume for
example that there are 1000 connections in a house. That is not at all an
unrealistic number. Now assume that only one connection out of every
hundred connections fails. That is a total of 10 failed connections.
In other words, 10 places where a fire could start. Poor electrical
connections are the leading cause of electrical fires. Would you want to
live in a house with 10 bad connections?
Attics are not only the most common place
to find junction boxes with poor connections. Electrical boxes in the
attic are also more likely to come into contact with combustible materials.
People like to store things in attics. We need to look carefully around
stored items. You can usually tell when something is stored directly on
top of an electrical box. Be sure to look around items too. You will
not be able to see everything but remember, you are looking for key indicators -
signs of trouble.
Attics may be the most common locations for
dangerous electrical connections but they can be almost anywhere.
Locations that are not in plain view under ordinary daily circumstances are more
likely to have sloppy workmanship than locations that are in plain view.
Some electricians who are properly trained may do good work in visible areas but
may cut corners in less conspicuous locations. You need to always be on
the lookout for signs of poor workmanship in the less conspicuous areas.
It is usually very easy for a trained
observer to spot amateur work. Amateurs don't know that they are doing
wrong so they make no attempt to conceal their deficiencies.
2. Device connections in receptacles and
switches (especially on perimeter walls)
This is where a hand held IR thermometer
can be very handy. Device connections should not be warmer than the
ambient temperature. A temperature difference of a few degrees is probably
acceptable. You need to take into account the load on the circuit at the
time. It is beyond the scope of a basic home inspection to open the box to
evaluate the wiring. Should you decide to go into doing invasive
electrical inspections, you might then remove an outlet to check the current
flowing. We will get into doing those types of checks in a later course.
For now, we are going to only talk about visual inspections.
I am going to split this discussion into
two parts. First, the basics. We will go into a little more detail
in the Part 2. The important thing to know at this point is that
connections to switches and receptacles are very susceptible to failures.
We old-timers (50+) like to talk about the good-old-days when device connections
problems were rare. Well, here is one area where modern technology has
taken us backwards in safety and reliability. Electrical contractors may
save a lot of money on labor costs but they save that money at the cost of
safety and reliability.
This is not a class about morality so I'll
stifle my opinions about current wiring methods. As home inspectors
though, we need to know what we are up against. Right now, I just need to
be sure that you understand the importance of this part of an electrical system.
As I mentioned in the previous section, poor connections are the leading cause
of electrical fires. Poor device connections rank right up there with
other poor connections in being responsible for fires. I'll talk in Part 2
about why device connections fail more often in perimeter walls than in interior
walls.
3. Loss of the grounded (neutral) conductor
in circuits with a shared grounded conductor (can impress 240V across 120V
circuits)
Illustration (PDF)
I have always had a strong dislike for the
word "neutral". The long established correct term has been "grounded
conductor". That is changing but for our purposes, let's stay with the
traditional terms. The term neutral is something of a misnomer. The
name seems to imply that it is not a current carrying conductor. Sadly,
many people have met their demise because they grabbed onto the white grounded
conductor assuming that it did not carry electrical current.
As a young electrician I always had an
objection to having two circuits sharing the grounded (neutral) conductor.
This is usually accomplished in residential wiring by running 14/3 or 12/3 NM
cables instead of two separate 14/2 cables of two separate 12/2 cables.
Whenever the boss wasn't looking, I'd run two 14/2's or 12/2's instead a single
three conductor cable.
True enough, it wasn't my money. It
was the bosses money I was spending. I was "talked to" on more than one
occasion about my expensive habit. When I later had my own electrical
business, I continued the practice. My crews were instructed NEVER
to share grounded conductors.
It always seemed like risky business to me.
Sharing the grounded conductor would not be a problem in a perfect world.
In a perfect world. The reason is that the grounded conductor can never
carry more than either one of the ungrounded (hot) conductors from the two
circuits. We will get to why that is in the next four hour course.
The important thing to understand right now is that when that shared grounded
conductor is lost - for any reason - 240V can potentially be impressed across 120V appliances.*
240V across a 120V appliance is not a good
thing. What happens will mainly depend what the appliance is. If it
is something like a PC, a television, or light bulb, the chances are that it
will destroy the appliance but will not necessarily start a fire. If it is
any thing with a heating element or a small motor, the chances of starting a
fire are much greater. Also, there is a strong possibility of starting a
fire at a device such as an electrical outlet.
Little did I know 30 years ago that I would
years later end up investigating fires caused by the loss of grounded
conductors. Sharing grounded conductors never seemed to be a good idea but
I certainly did not know at the time that loss of grounded conductors really is
a leading cause of electrical fires.
* Appliance refers to any
electrical load. It can be anything from a table lamp to a PC to a clothes
washer.
4. Loss of the grounded (neutral) conductor
in branch circuits because of poor joints (connections)
Illustration (PDF)
We have already covered the topic of poor
joints so you know that they are inherently hazardous. The usual problem
is heat. An improper joint is presented to the system as another load.
A bad connection is like having a small heating element. Obviously, that's
not a good thing. What if that bad joint also happens to be connecting
segments of a shared grounded conductor together? There are two potential
problems. One potential problem is heat. The other potential problem
is the loss of the grounded conductor.
Have you ever used a continuity tester to
check the integrity of an electrical circuit? If you have I am going to
ask you to stop the practice right now. Please, just trust me on this one
for now. Later you will be glad you did.
A bad joint will often appear to be good
when checked with a continuity tester. We don't want to get side-tracked
with talking about the reasons for this now. For now, you need to accept
this as fact so we can continue with the lesson and not have you confused when
you are in the field looking at these types of installations.
Let's first take a look at how you can
recognize a shared grounded conductor. As I mentioned earlier, the usual
practice is to use three conductor cables. Whenever you see a three
conductor NM cable entering a junction box, ask yourself these questions, "Are
there any 240V loads coming off this box?", "Are the cables going to a kitchen
or a dining room?", "Are there possible three-way or four-way switch legs that
may in the box?"
The presence of three conductor cables
where there are no 240V circuits is a good indication that there may be shared
grounded conductors. However, three conductor cables are often used for
switch legs too. If you are using a IR thermometer, check the
temperatures. Cool temperatures do not necessarily mean that everything is
OK but it is better to have cool temperatures than warm or hot.
Don't forget that you will not see any
appreciable temperature rise unless there is a significant load on the circuit.
The reason is that the connections are in series with the loads. You would
certainly see something going on if they were in parallel! We will go into
why that is in a more advanced course. For now, just remember that the
fact that a box is cool doesn't mean much if there is not appreciable load in
the circuit while you are checking it.
5. Compromised grounded (neutral conductor)
in branch circuits because of poor joints (connections)
Illustration (PDF)
Have you heard the word "Common" used when
referring to electrical wiring? At one time, the grounded conductor was
called "the Common" about as often as it was called "the Neutral". For
whatever reason, the term has become much less popular than it used to be but,
it is still in use. Common is really a better description than neutral.
It more accurately describes what the grounded conductor is. It is a
conductor that is common to all the circuits in an electrical system.
There are some exceptions to this but they are beyond the scope of this course.
For residential electrical systems, the grounded conductors are usually all
common. That is, they all eventually tie together.
Nowhere is that more evident than in
junction boxes. It is a common practice among electricians to tie all the
grounded conductors together in a junction box. Solderless connectors are
rated for use with specific sizes and numbers of conductors. It can be a
real challenge to put half a four or more wires in a single Solderless twist-on
connector.
I've already mentioned that one of the
signs of amateur work is tape on the connectors. Another possible sign of
an amateur is twisted wires. Wires being twisted together under a twist-on
connector are not a sure sign of an amateur. Many qualified electricians
also twist their wires. However, amateurs almost always twist their
wires. Most manufacturers of twist-on connectors say that it is acceptable
to twist the wires but that twisting is not required. Some may even
recommend or require that the wires be twisted. So, when you see wires
twisted together you need to also take into consideration other workmanship
clues. Wire that are not twisted together are usually a sign of a
professional installation.
Having personally made many thousands of
connections using twist-on connectors, I take great care not to allow the wires
to twist together. I can get a superior connection by keeping the wires as
straight and parallel as possible.
Of course you won't see any of the
connections if the cover is on the box and you are not going to be taking covers
off. When you encounter a box with no cover, you will know what to look
for. Be very suspicious of four or more grounded conductors all tied
together with a twist-on connector.
I cannot stress enough that these
inspection tips are not going to enable you to definitely identify wiring
problems. They are clues. Being a home inspector means being a
detective. You have to understand how first how to recognize the clues
then, how to analyze them.
6. Other causes of loss of the grounded (neutral) conductor
Back when I was a young electrician
concerned about sharing grounded conductors, my main reason for concern was not
that the neutral would be lost. I was confident in my own work so I was
not thinking about the failure of my joints. What I envisioned was future
alterations that would compromise or overload the grounded conductor.
In order for a shared grounded conductor to
be safe (and legal), the two ungrounded (hot) conductors need to be from
opposite phase legs. The two ungrounded cannot be on the same phase
leg.
I spent much of my apprenticeship and
earlier years as a journeyman doing what is referred to in the trades as "old
work". In other words, rewiring buildings. I also started doing a
lot of service calls early in my career. While most of my coworkers
preferred building electrical systems I preferred to troubleshoot them.
What I found while doing service work was
that circuits would often be rearranged so that what were once safe circuits
were no longer safe. A major culprit in modern systems is tandem breakers.
Electrical panels are laid out so that the poles on each side alternate (phase A
- phase B - phase A - phase B, etc). The reason for this layout is so
two-pole 240V breakers can be installed. The grounded conductor in a 240V
1θ (Single phase) system is a true neutral thus, the current it carries
is always less than the greater of the two phase legs. The neutral only
carries the difference between the two legs. Don't worry about why that is
right now. The important thing to know and to remember right now is that
the poles alternate.
What do you think will happen when you
replace two individual with a single space saving tandem breaker and the two
circuits had been sharing a neutral? The two circuits have been placed on
the same phase leg. So, instead of carrying less than the current
being carried by the greater of the two phase legs, it is now carrying the
total current of the two phase legs.
Here is an example. Let's say you
have two 15 amp circuits on adjacent breakers in a panel. One circuit has
12 Amperes flowing in it and the other has 13 Amperes flowing in it. Their
shared neutral is carrying the difference of only one ampere. Now
let's say that you replace the two individual with a single space saving tandem
breaker. The shared neutral is now carrying 25 Amperes on a circuit rated
for only 15 Amperes. This is not a good thing!
I cannot even begin to estimate how many
times I have found this very serious problem in the field. Sometimes it is
very easy to see whether or not the two circuits on a tandem breaker are sharing
a grounded conductor. Sometimes it is not easy to see. If the
circuits on the tandem breaker are entering the panel in three conductor NM
cable it is easy to spot the problem but, what if they are coming in with other
circuits in a conduit? You are not going to be able to readily identify
the problem if it exists. The only easy and reliable way to quickly
identify the problem would be to place loads on both circuits and check the
neutral currents in the conduit that contains the circuit conductors.
Most home inspectors remove the electrical
service panel cover during an inspection so it would not be too difficult to
carry a clamp-on ammeter to perform this check. However, it is beyond the
scope of a typical basic home inspection being done according to industry
standards to perform such checks. The decision is yours. I guarantee
you that if you do this check, you will be catching some things that most
inspectors routinely overlook.
The last thing I want to discuss in this
section is double tapping. I am going to be very blunt about this.
It is my single greatest concern with home inspectors doing electrical
inspections. The loss of a neutral is serious business regardless of how
or where it happens. One way in which a neutral can be lost or compromised
is by coming loose at at the busbar in the service panel. Double tapping
can increase the chances of the conductors becoming loose.
What concerns me is that there is so much
talk about double-tapping and so much made of it during inspections while so
many of the other more likely potential causes of a catastrophic failure are
completely overlooked. The integrity of the terminations, double-tapped or
not, is very often overlooked. A habit I have is to start checking the
terminations whenever I open an electrical service panel.
People rarely think to do routine
maintenance on a an electrical service panel. Any panel five years old or
older that you open is very likely to have grounded conductors that are not
properly secure. It doesn't matter if they are double-tapped or not.
It is far more important to know whether or not the conductors are secure
than to be concerned about the fact that there are two wires under screw.
You are there to do a home inspection, not
to perform maintenance on the panel. If you find a single screw that you
can turn a quarter of a turn, you need to recommend routine maintenance on the
service equipment. Routine maintenance should be performed at least once
every five years.
The neutral conductor is not only lost or
compromised in branch circuits. It is also at risk in service equipment,
electrical feeders, and subpanels. Failures on utilities poles are not
uncommon. The grounded conductor can also become loose in meter sockets
and panels. Loss of a neutral in the service panel or upstream of the
service panel is extremely dangerous because the entire 120V distribution in the
house can have 240V applied across it.
Even if you don't check for too many wires
under a twist-on connector, rearranged circuits, or check for excessive current
on a neutral conductors you need to be aware of the ways in which a the neutral
can be compromised or overloaded.
7. Recessed lights
Recessed light fixtures and cellulose
insulation do not go well together. Wait a minute ... Most recessed light
fixtures have thermal protection and cellulose insulation is not flammable so
there shouldn't be a problem, right? Well you would think so. Once
again, in a perfect World, that wouldn't be a problem. The thing
is, we don't live in a perfect World.
Let's first consider the thermal overload.
The thermal over load is a small device situated in the can so that it senses
temperatures above a safe limit. Changes have been made to recessed light
fixtures over the years. They are much safer today than they were only a
few years ago. Some of the older recessed fixtures had the thermal
overloads inside the can but off to the side. There can be a problem with
the fixtures because heat rises. It is possible for the sensor to not be
exposed to temperatures as the surfaces, especially the top, of the can.
The thermal overloads are often exposed and they may have been moved during the
installation. It does not take much movement to impair the overload's
ability to sense dangerous temperatures in time to prevent a fire.
You are not going to see the overloads in
recessed fixtures during an inspection. You need to be aware of the
potential danger though. Some fixtures are rated for direct contact with
insulation. The fixtures that are rated for direct contact with insulation
are usually the bigger boxier styles. The older fixtures usually had
smaller cans. The cans are often round and have a domed top. There
are still many thousands, perhaps millions, of the older style fixtures still in
use.
What about the "non-flammable" cellulose
insulation? Non-flammable does not mean that it doesn't burn!
Non-flammable means that it will not support a flame. It will smolder.
Cellulose insulation can smolder for a very long time; days or even weeks.
Burning cellulose will cause "tracking" or "veins" of burned cellulose that can
go very long distances. Eventually the tracks will reach a combustible
material and will surface. When they do, a fire starts.
I did a fire investigation a few years ago
in a large home, perhaps 10000 square feet, that was in the process of having
some redecorating and minor renovations done. The house was only a few
years old. It had cellulose insulation in the attic. It was a two
story house. The total attic space was around 5000 square feet.
A small fire had broken out several days
earlier but the fire department had arrived and the fire was very quickly
extinguished. The fire has broken out on the second floor. There was
almost no structural damage. Most of the damage was from smoke. In a
larger fire, the fire fighters will normally perform what is called "overhaul".
that is, they sift through debris searching for any remnants of the fire.
They don't want to leave smoldering debris behind that could cause the fire to
flare up again. There didn't seem to be anything to do overhaul on with
this fire.
The insurance company hired us to
investigate the cause and origin of the fire. There were no sources of
ignition near where the fire broke out. The closest electrical loads were
at least ten feet away. At first glance, it looked as though it would be a
poor connection in an attic mounted junction box. In houses that have
cellulose insulation, Most of junction boxes are usually buried in the
insulation. It can be a long tedious process locating them.
I gently sift through the insulation with
my had and a long cabinet tip screwdriver to find the junction boxes. What
I found in this house was hot tracking - and lots of it! The insulation
was smoldering in dozens of places. The house could literally have burst
into flames at almost any time. I located a recessed fixture that was the
cause of fire. It was new style fixture with a thermal overload mounted in
the top section but the overload had failed.
Insurance companies do not always
investigate fires this small. In this instance it was a good thing they
did. I recommend 3" of clearance for all recessed light fixtures; even if
they are rated for direct contact with insulation. Insulation should never
completely cover a recessed light fixture. If you see recessed fixtures in
the living area, you should see them in the attic too. Sometimes the
tracks burn themselves out because they reach an ignition source. they
need both a combustible material and oxygen. Sometimes the tracks
will end at a combustible material, such as a wood truss, that never catches
fire. That is because the tracks are usually below the surface and the
combustible material is smothered in the insulation. The track needs to
find an oxygen source to ignite the combustible material.
Should you ever encounter tracking, do
not expose it. You don't want to expose the tracking to oxygen.
Leave the attic, evacuate the house and call the fire department. The
section of tracking you find may be cold but that doesn't mean that there are
not live (smoldering) tracks somewhere nearby. The tracks may have been
there for weeks, months, or even years. You will have no way of knowing.
You may never get another referral from the real estate agent but that's better
than waking up a few days later to learn that someone died in a house fire in a
house that you just inspected.
8. Halogen lights (not part of the
electrical system but a major cause of electrical fires)
I am not going to say much about Halogen
lamps. The ones that most often cause fires are portable. They are
placed too close to curtains or other flammable materials or they are knocked
over. They usually have a small stand-of to prevent them from being in
direct contact with combustibles when they fall over but they can still cause a
fire quickly if left undiscovered. Look at permanently installed halogen
lighting to make sure that it is not too close to combustible materials.
9. Clothes dryers (not part of the
electrical system but a major cause of electrical fires)
You are probably already know that clothes
dryers are responsible for thousands of house fires every year in the U.S. and
Canada because of lint in dryer vents. Are you also aware that many dryer
fires are caused by lint getting into the heating element housing of electric
dryers? Take a clothes dryer apart sometime. You might be amazed at
what you find. If you inspect appliances as part of your home inspection,
you need to know about the hazards of clothes dryers.
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Recommended reading:
ELECTRICAL FIRES
by
John Gardner
http://www.tcforensic.com.au/docs/article11.html
Recommended videos
Examples of the destructive power of electricity:
Large Electrical Explosion Live on News
http://www.youtube.com/watch?v=eYUmdqQ94Ao
http://www.youtube.com/watch?v=EochMYzYz20
http://www.youtube.com/watch?v=BhTz7YMgDXM
http://www.youtube.com/watch?v=yaSPaF7n-OE
http://www.youtube.com/watch?v=-iClXrd50Z8
http://www.youtube.com/watch?v=THT5al8kaLk
http://www.youtube.com/watch?v=OY72athcwvA
http://www.youtube.com/watch?v=2_4gsPe7BuM
Multimeter without fused leads
Multimeter Explosion
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