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Power strips


In my studio, I had a wood stove, somewhat funky electrical wiring,
a gas furnace - several torches, from propane, to Little Torch
propane/oxygen, to air/acetylene, to oxy-acetylene.

I cut rocks so have many electrical machines for grinding and
sawing. I’ve got wires everywhere, lights hanging everywhere. Lots
of little heaters for lots of different things, like pickling or
cleaning stones, or you name it. Hair dryers for heating and glue
pots and dopping lamp. In other words I have an amazing assortment
of things that can cause fire. And then of course there are all the
solvents and glues and finishes for stone and wood.

And this morning I had a fire in my studio caused by a faulty power
strip. The Vermont Fire Marshall came to my studio today and told me
that my fire started in the power strip and that lots of fires start
in power strips.

I purchased my fire strip to avoid fire. Apparently it’s necessary
to replace them every year or two or they can catch on fire. Not
only that but this is not generally available because it
doesn’t say so on the strip or the packaging.

I had quite a bit of damage and at some point will have to have a
fire sale of stones to try and recover much of the equipment in my

But in the mean time folks, replace your power strips. And buy good
ones. I think mine was UL approved and I don’t overload mine. One or
two things on them and nothing very heavy.

Yes I had insurance on the building, but not on the contents because
that was very expensive.



Derek Levin


I am so sorry about the fire. Thank you for thinking of and warning
us. Hopefully, someone will be saved from the heartbreak you are
experiencing now.

Bobbie Horn


Ah yes, the dangers of power strips.

A properly designed power strip will not start a fire even after it
fails to protect. The cheap ones are all too likely to start a fire
when they fail.

The reason is that the protective elements in a power strip are
almost always varisistors (plus other things in higher quality power
strips). Varisistors are disks about the size of a quarter and when
they fail they often split open. Since they are in effect sacrificial
elements in cheap power strips they inevitably fail.

When the varisistors fail you lose any power protection in the
strip. However that’s not what starts the fires. If the components
are packed too tightly, as they often are on cheap power strips, the
parts of the split varisistor can be held in close enough proximity
to provide a current path, overheating and fire.

Best practice is 1) don’t buy cheap power strips and 2) replace any
power strips with “power protection” at least once a year.

Note that an ordinary multi-outlet extension cord doesn’t have this
problem because it doesn’t contain varisistors. For most equipment in
the shop multi-outlet cords are better. (And proper wiring with
enough outlets is best of all)

Ironically, it’s very difficult to get people’s attention on the
problem. I’ve proposed articles on it several times to magazine
editors and been repeatedly turned down.



While speaking of fires, I have something to add. Please make sure
your fire extinguishers are up to date. This can mean that you have
new disposable ones (write the date of purchase on it!) or
refillable ones with current inspection tags. We recently had a fire
in our kitchen and the first extinguisher did not work. It was very
old. Luckily, I had a new extinguisher on the porch that did work, so
the damage was fairly minor.

Also, make sure you have the proper type of extinguisher for the
area it is for by reading the labels.

When I do shows, the fire marshal generally requires that the
extinguisher have a purchase receipt less than 1 year old or a
current inspection tag.

Old non-refillable extinguishers need to be discarded, but you may
have to check with your local officials or fire department to find
out how to dispose of them. Many areas have a ban on putting them in
the regular trash.

Mary Ellin D’Agostino, PhD
Sr. Teacher, PMC Connection
Certified Artisan, PMC Guild


If you have to rebuild your shop you can wire in a master kill
switch, shuts down the whole room with one flick at the end of the
day. (I take it you were not in the shop when the fire started). And
get some proper wiring. Hot wires draping over each other is another


I will be honest, I don’t like power strips period, for anything
that takes any significant amperage. They are just made too light for
the job you are asking them to do. If the outlet heats the least bit
very quickly (while still working fine) the temperature where the
plug is inserted and makes contact with the outlet inside zooms and
will cause burning and arcing. As a test plug something in and run it
for 10 minutes and then pull the plug out and touch the prongs. If
they are hot, then toss the bar or outlet. The other problem with
consumer power bars is that they are made if plastics that melt (and
will catch fire) at a lower temperature than a wall outlet.

Also Inspect the plug prongs, any with pitting or burn / arcing
marks should be replaced, as they will cause a new outlet or power
bar to fail very quickly.

An additional point power bars are generally rated at a given
amperage for the entire bar, individual outlets have a much lower

In my opinion especially now that you are rebuilding, either have an
electrician (or do it yourself) Wire a series of outlet boxes
separated by a 4 or 6 inch piece of conduit between each to make a
long fully rated power bar. Or buy a Shop rated power bar with
realistic ratings for each outlet. I think however when you see the
price for one you will go with the outlets instead.

A final thought, if you have the electrician do you a special
circuit or 3 with multiple outlets for your bench areas, ask him to
use GFI breakers in the panel. The additional cost is minimal and the
protection in case of insulation failure in one of your tools is well
worth it. Also if you have something arcing internally then odds on
favor it will trip a GFI breaker long before it would trip out a
regular breaker.

From Snowy Quebec, looking at Snowy Vermont 2 miles south of me


If the components are packed too tightly, as they often are on
cheap power strips, the parts of the split varisistor can be held
in close enough proximity to provide a current path, overheating
and fire.

This is interesting and helpful, and I thank you. But-- how do you
tell a “cheap” strip from a “good” one? Not by price, really,
surely. One can find the exact same, or same-appearing, things for
all different prices in our marketplace. Being charged a lot is no
assurance, despite the old saw about getting what you pay for. I
prefer to say, “You may not get what you pay for, but you don’t get
what you don’t pay for”. My (phylisophical and intellectual) husband
would say, price is an incidental, not an essential quality.



Hi Rick,

When I showed this to my husband he responded as follows (he is a
Master Electrician):

I believe what you are referring to, is a MOV, which is short for a
Metal Oxide Varistor. Equipment such as universal motors or motors
without a commutator can stand to have up to 5% voltages higher than
what is specified on the name plate without damage to the motor.
They also have an inrush current in the vicinity of 3 times the
normal operating current during start-up and lasting for a few
seconds. I agree that Multi-outlet assemblies (MOA) should not be
used for these devices as the inrush current is hard on many parts of
the assembly including the supply cord. The manufacturers of some MOA
devices include a circuit breaker to prevent hard start situations.

Multi-outlet assemblies are intended for use with anything
electronic as these appliances will not tolerate voltages higher than
the standard 120 Volts under any situation. That is where the MOV
comes into the picture. If a voltage spike is headed down the
conductors to your Multi-outlet assembly that is higher than 120
Volts, the MOV will short any voltage between 120 Volts and the
higher voltage directly to ground. Unfortunately, even higher priced
assemblies use cheap MOVs and reliability is in question.

Home Depot sells a line conditioner for about $150 Canadian funds.
It can be connected to the 1st two circuit locations in the house
panel and will give surge and spike protection to every outlet in the
home. It has on-board LEDs which indicate that the self-diagnostics
of the unit are functioning and the unit is on-line or in other words
it is in the process of protecting your entire electrical system.
When considering the total value of all electronic devices in a
standard home, it is not good to be without the line conditioner.

I applaud your efforts to spread the word about electrical
protective devices.

Regards, Dan Bahr

Karen Bahr - Karen’s Artworx
Calgary, Alberta, Canada


A very provocative thread. I do have power strips in my basement
studio…gonna check them out today. However, when I had my garage
insulated, drywalled, painted, new lights, for a teaching studio, I
had an electrical company come in and wire it for 70 amps. I have a
breaker box installed in the garage for the eight multiple outlets -
(three workbenches) - I have for 2 burnout ovens, flat laps, saws,
drill press, and general appliances. It meets all the codes and gives
me much satisfaction that I am “protected”.

I once knew of a couple who had a kitchen fire while leaving a
coffee pot on an automatic timer. This little item is something that
should be checked periodically and replaced…just as another heads up
in electrical mishaps.

Rose Marie Christison


I have my shop wired with multiple outlets, much as Kay in Quebec
mentioned. I found after building, however, that my area is
particularly lightening-prone, and I now have anything that costs
over $10 on a surge protector strip. These come with built in safety
kick offs, and insurance up to certain limits for anything plugged
into them that gets zapped by power coming through them when it
should not have.

I have not had to file a claim, but buy a steady supply of these
strips as they DO shut off when zapped… and then you must replace
them. Much cheaper than replacing all my equipment!

I also had the power company add a surge protector to the outside
where the power line joins my building line. This has been blown
numerous times too. I am at the end of the power line in the
country, and if lightening or an industrial surge hits the line, it
comes out at my house! NOT fun!

From balmy SC where I’m in shorts and a t-shirt hoping it really
does rain today!

Beth Wicker
Three Cats and a Dog Design Studio


If the on/off switch is in the off position, are they still a
hazard? Even with the better ones?

I have some which I leave plugged in but turned off when not in use.
Usually with nothing plugged into them. My reasoning was to eliminate
the power to the receptacles thinking that would be better than
having a live multi-outlet extension cord.



How do you tell a good power strip from a cheap one?

  1. Read the specs carefully.
  2. Weigh it in your hand, The heavier the better.
  3. Price. Yes, there is a correlation.



In reference to lightning protection that some of the Power bars

It is limited at best. In addition to the electric company’s
lightning suppressor you can have one installed on your electric
panel which will not only give whole house protection but is better
able to handle the surges.

One must make a difference between an electric companies lightning
arrestor which typically kicks in at 5 or more time the rated line
voltage for low voltage circuits (<600V) and 2 times for high
voltage. (At least these are the Values that Hydro Quebec gives).
These will usually prevent lightning caused fires and protect utility
equipment but will still fry electronic equipment in your house.

A surge protector will clamp the voltage much closer to line voltage
and do a better job protecting your equipment.

We have several clients who are in extremely lightning prone areas
(one client is 150 feet from the edge of a 500 foot cliff overlooking
a large wide river valley… needless to say when the storms come
across the valley his dealership is usually ground zero for some
nasty hits. The only way we have found there is to have a interrupter
switch between the main panel and the sub panel feeding his computer
gear. In this case the interrupter switch must be the old fashioned
knife type (you want a big air gap), not a simple circuit breaker
with a 1/4 inch air gap inside (just show this to your electrical
contractor, he knows what it means). If you have your studio on a
separate sub panel as some posters mentioned they have, using a
interrupter switch to kill all power to the benches and equipment,
guarantees nothing is left on or that if there is a nasty storm, that
your equipment will be safe. I would have lighting and heat not on
this panel so they still work

As Chuck Yeager used to say in the AC Delco advertisement, Pay me
now or Pay later…




My husband, an electrician, told me when we first got together that
those surge protector strips, while better than the others, are
still not enough, especially on computers and television/stereo
equipment. About a year later I saw the same thing mentioned in a
Consumer Reports magazine plus it is apparently really hard to get an
insurance claim paid out by those companies. I still have one for my
computer on top of a line conditioner (surge protector) by Cutler
Hammer, (comes with a warranty too) which is good for the whole
house, and it works on electrical, telephone and tv cable
connections. Especially in older houses (built in the 30’s -50’s)
many houses telephone lines acted as lightening rods to start home
fires. As the electrical companies start to cause ‘brown outs’ to
handle problems from the need exceeding the supply demand on
electricity this becomes even more important.

My husband responded a couple of days ago on this thread to explain
more about the power bars.

Karen Bahr - Karen’s Artworx
Calgary, Alberta, Canada


I’ve done some wiring, but I’m no expert, so I’ve kept quiet, here.
With the discussion here, though, I thought I’d type up what’s
pinned up on the wall:

San Francisco Fire Code Section 8507. The use of multiplug adapters
such as multiplug extension cords, cube adapters, strip plugs or any
other device, which is listed as a temporary power tap shall not be
used as a permanent wiring and shall be unplugged when appliance
connected to it is not in immediate use. Surge suppressors listed as
permanent wiring may be used on electronic equipment only and shall
be plugged directly into approved electrical receptacle. Cease the
use of any extension cords or any other device that is being used as
a permanent means for electrical equipment.

The last because we are inspected annually, and have corrected the


Everybody probably knows the difference between a surge protector
and a plain-old power strip, I hope. Years ago I was sitting in this
very spotat my old pentium 2 when there was a power surge. Not
lightning or anything,the lights just glowed twice as bright for 10
seconds or so. Completely fried the hard drive on my computer,
turned it into a door stop. Ever since I’ve had a good surge
protector - nothing exoticor really expensive, just a good one.


With all this talk about cheap power strips, I was really worried
about my set-up, where all my bench applicances (crock pot,
ultrasonic cleaner and flexshaft) are plugged into a four port power
strip purchased from Ikea very cheaply. So I copied all the emails on
the subject and sent them to my husband. He assured me that there’s
nothing to worry about. Apparently things are a bit different in the
UK. First of all, our mains system runs on 240V rather than the US’s
110V. Every electrical device must be individually fused too, so
each appliance has the correctly rated fuse fitted in the plug,
including power strips. It is illegal to sell any electrical
appliance in the UK which doesn’t conform to British Standards, no
matter how much or little they cost - they must comply. Our plugs can
draw more current than in the US and if there’s a power surge, the
fuse will blow.

I’m afraid I’m rubbish at physics and still get confused with the
relationships between voltage, current, power - so forgive me if
I’ve got anything wrong. I refresh my pitiful knowledge every now and
then but have a mental block and so quickly forget it, so please
don’t write telling me. :wink:


The reason is that the protective elements in a power strip are
almost always varisistors (plus other things in higher quality
power strips). If the components are packed too tightly, as they
often are on cheap power strips, the parts of the split varisistor
can be held in close enough proximity to provide a current path,
overheating and fire. 

Whew. That’s incredibly important I’d bypass the
magazine editors and go straight to wikipedia with it.

Thank you!