Monthly Archives: December 2011

Many people when they need more outlets grab a power strip.  They don’t really consider what the load is they’re running off the strip as a whole.  Many will do the worst thing in the world and cascade power strips for more outlets, or plug a very large current item into the power strip.  There’s a couple things going on that make ignoring these factors a bad idea.  The biggest is that this is the result.

The cause:

According to fire investigators, a power strip started the fire, which caused an estimated $250,000 in damage. Multiple computers and a space heater had been plugged into the strip, but what role that played remains uncertain.

I’m going to explain now exactly why cascading power strips, and ignoring load concerns is a bad idea and results in the above.  First read this article on an introduction on basic electronics.  In doing this I’m also going to explain why you never replace a circuit breaker or fuse with anything but a matching value.

Power Losses A Quick Reminder:

Did you see the section involving wire diameter, length, and overall resistance?  There’s a minimum wire gauge for carrying different loads of current.  The reason being is power losses over the wire.  Remember the equation, I²R.  This can be used to determine power lost over the wire is dissipated in the form of heat.  Lets start off with a simple example.

A Base Load Example:

Residential building codes state that for a 12 gauge wire the maximum current load is 20 amp breaker.  We have a computer using a 650W power supply and two LCD displays (~75W). These three are plugged into a single 14 gauge surge protector plugged into an outlet on the 20 amp circuit.  Now while that 650W supply may not be operation at full load, we will assume it is for calculation purposes.

Circuit breakers are rated to carry 80% of their rated nominal load continuously.  This means that our breaker can supply 16 amps continuously to our load distribution the power strip.  This works out to be 1760W = (20*0.8)A*110V that the circuit can supply.  Though the surge protector can only safely deliver 1320W = (15*0.8)A*110V due to it only having 14AWG wiring.  Most power strips will have a safety breaker that will enforce this limit, however they can fail and on cheap strips they may not even work.  Currently our load is only 800W so we are well within the safe range.

How Easy It is To Cross the Threshold:

Now lets say we want to add a space heater since the wife is cold.  If we add the 800W oil heater to out power strip with our computer.  This moves the load on the power strip up to 1600W.  This is beyond the 14 AWG capacity of 1320W.  This will cause the temperature of the wires to go beyond their rated values.  This can be a serious problem if the power strip is located in an area where heat cannot dissipate.  The addition of the power strip also adds extra length increasing your overall I²R losses.  This is why you don’t want to put a large load such as a heater on an extension cord.  If you do, make sure it is a heavy grade extension cord.  The safest method is to plug it directly into a wall outlet.  This will still be below the 20A continuous rating, prevents the extra I²R loss from the extra length, and doesn’t overload the the smaller power strip.

So What About Cascading Them:

Now so far we’ve only been really talking about a single power strip, what happens when you cascade them?  This is where another lesser known problem rears it’s head.  The majority of heating in house hold power distribution circuits are at junctions.  Where wires are tied together, plugs and outlets, and screw terminals.  This is because the resistance in the joint higher than the surrounding materials.  Again, I²R comes in to play with the larger resistance at the joint.  That power goes somewhere and it is released as more heat into the system.  So adding extra power strips increases the resistance in the line and increases the overall power losses.

So What About Circuit Breakers:

Now how does that apply to circuit breakers though.  Say instead of a 12 AWG circuit with a 20A breaker it’s a 14 AWG circuit with a 15A breaker.  It keeps tripping and you think it’s faulty.  All you have in your chest to replace it is a 20A breaker.  You have now allowed a much larger current to flow across the circuit that it is safely rated for.  You have upped the trip limit from 12A to 16A, thus your I²R loss is going to increase.  That increase of 4 amps increases the power dissipation required of the wire by 1.7x.  Again that power is dissipated in the form of heat, in your walls, that retain heat, some packed with insulation.  You have turned your house wiring into a toaster element, not a good idea.

Final Overview:

So there’s a rough idea of 

1. Why you don’t cascade power strips.
2. Why you plug high power appliances into the wall, or use a large gauge extension cord with a single outlet.
3. Why you don’t swap a smaller breaker for a larger one.
4. The physics behind what cause the fire above.

TMM

TMM is the owner, editor, and principal author at The Minuteman, a competitive shooter, and staff member for Boomershoot. Even in his free time he’s merging his love and knowledge of computers and technology with his love of firearms.

Many know his private name and information however due to the current political climate, many are distancing themselves due to the abandonment of Due Process.

www.the-minuteman.org

When you see something like this, you know the overlords at the City and County level don’t like being told to stop being petty tyrants.

Palm Beach County Tuesday filed a lawsuit challenging the Legislature’s ability to penalize local officials for regulating guns.

That’s the problem right there in a nutshell.  Our government is designed to have limited enumerated powers.  When a politician steps outside those powers they are not held accountable.  Instead money comes from the taxpayer to pay for the grievance.  Doesn’t matter if the law maker knew the laws were illegal, they get off free.

Sounds like the people of Palm Beach County need to break out the tar and feathers since the law makers there think being financially liable is a problem.

h/t Dave Hardy

TMM

TMM is the owner, editor, and principal author at The Minuteman, a competitive shooter, and staff member for Boomershoot. Even in his free time he’s merging his love and knowledge of computers and technology with his love of firearms.

Many know his private name and information however due to the current political climate, many are distancing themselves due to the abandonment of Due Process.

www.the-minuteman.org

Once is happenstance, twice is coincidence, three or more times is enemy action.  Well I don’t believe in coincidence and at this point it no longer matters.

Yesterday another elderly woman came forward saying she received the same type of treatment as the 85 year old grandmother.

Ruth Sherman, 88, of Sunrise, Fla., told WCBS television ( http://cbsloc.al/sD3xsS
) that agents were suspicious about her colostomy bag and asked her to pull down the waist of her pants so they could see it on Nov. 28.

So that’s twice.  Today a third woman has come forward describing the same type of treatment, this time over a glucose monitor.

Kallish’s troubles began because of the glucose monitor and insulin pump she wears because of her diabetes. After she set off the metal detector she was sent to a private room and, she says, told to take her pants off. She says the officer didn’t touch her. “So I took my pants off and showed [the glucose monitor] to her,” Kallish said. “She just looked at it and said, ‘Have a nice trip.'”

That’s three.  The TSA claimed on Friday that strip searches as the above are not procedure.  However in all three instances there was an underlying medical condition that the officers exploited to abuse their power.

At what point do people finally say enough is enough.  How much abuse do the public have to take before someone finally wises up that while the TSA may claim that something is not policy or procedure doesn’t mean that it doesn’t happen.  TSA agents don’t follow normal policy or procedures regarding the use of equipment that make use of radio active equipment, why does anyone think they would magically follow their own rule book?

This is like playing Monopoly with a kid who is making up his own rules and constantly changing them.  Except this kid can throw you in jail when you point out he’s breaking the rules.  How do you deal with a spoiled brat who harasses and intimidates anyone who dares challenge their Authoritah.  Not to mention when you tell their parents about their kids misbehaving they just pat them on the back and say stop that.  Even when one of the parents is hassled.

My father-in-law was told not only to remove his prosthetic leg, but they wanted him to disassemble it.  There’s no cosmesis, and the leg requires special tools to assemble and disassemble.  If you’ve ever seen a bare prosthetic there is no room to put anything in it.  The TSA claims that type of behavior would never happen yet it does. 

This is what happens when you create a job program for the lowest common denominator who cant even graduate high school and give them more power than they know what to do with.  Then the parent who gave them that power says that there’s no accountability.

TMM

TMM is the owner, editor, and principal author at The Minuteman, a competitive shooter, and staff member for Boomershoot. Even in his free time he’s merging his love and knowledge of computers and technology with his love of firearms.

Many know his private name and information however due to the current political climate, many are distancing themselves due to the abandonment of Due Process.

www.the-minuteman.org