I’ve been putting the final touches on a new computer system with three
monitors and a 750 watt power supply. The printer is 600 watts, the
monitors are 170 watts, I have a TV on the other side of the wall
that’s 250 watts… add it all up to a usual load of about 15.3 amps. If
I turned on lights, amplifiers I can run the total up to 30.1 amps.

The circuit is 15 amps. :- (

And… I’d like to run all the computer equipment through one outlet so I
can unplug everything when the thunderstorms come.

So, I have a lot of questions:
1) First, why did the computer act like it tripped an overload in its
power supply, most of the load was outside of the computer? Why didn’t
the residential breaker trip instead?

2) Can a breaker cut the load for a second without mechanically
flipping to the off position?

3) I seem to remember some people just replacing the 15 amp with a 20
amp breaker when things get tight, is that a dangerous/stupid idea?

4) Does anyone see a problem running about 13 amps through one
household outlet in a tree of several power strips?

Should I increase my fire insurance coverage? :- )


--
Dallas

The issue isn't how much current is drawn through one outlet, but how much
current flows through the breaker feeding that outlet.

Two points...

The computer's 750W supply is rated at its maximum capacity. Unless you have
a high-end graphics card and are overclocking the system, it's unlikely
you're pulling 750W. Get a cheap power meter and see what the actual draw
is.

You should absolutely /not/ have a computer system and a high-powered HT
system on the same circuit breaker! Bad idea. If you can't power either one
off its own breaker, you should probably pay an electrician, to set up an
additional line with its own breaker. When my condo was built, I had a
separate breaker installed for the rear power amplifiers.

In article ,
Dallas wrote:

So, I have a lot of questions:
1) First, why did the computer act like it tripped an overload in its
power supply, most of the load was outside of the computer?

At a guess, the external load may have dragged down the voltage at the
outlet far enough that the computer power supply's "line undervoltage"
circuit kicked in, and shut down the computer cleanly.

Why didn’t
the residential breaker trip instead?

Residential circuit breakers are typically of the "thermal" type.
They require some amount of time to react to an overload... the higher
the degree of overload, the slower they trip.

This allows a circuit to have a momentary over-current (e.g. a
refrigerator drawing a surge of current when it first starts up)
without repeatedly tripping the breaker.

"Magnetic" circuit breakers will trip very rapidly in the face of even
a short overload... but I believe these are rarely found in
residential applications.

2) Can a breaker cut the load for a second without mechanically
flipping to the off position?

Typically, no.

3) I seem to remember some people just replacing the 15 amp with a 20
amp breaker when things get tight, is that a dangerous/stupid idea?

It is quite possibly both dangerous and stupid, and likely illegal.
The circuit breaker is supposed to be selected to be below the upper
limit of what the circuit wiring and outlets can handle safely.

If you draw more current than the wiring and outlets are designed to
deliver, you can suffer excessive voltage drop in the wires (lights
dim, motors slow down, and devices with "low line voltage" shutdown
circuits will shut themselves off. The wires can overhead. Also (and
perhaps more of a problem), the outlets themselves can overheat.

Now, it is *possible* that the wiring and outlets in your house are
actually rated for higher amperage (or that the outlets could be
upgraded for this). If so, it *might* be possible for a licensed
electrician to confirm this, and then swap out the lower-rated outlets
and breaker to increase the branch current level. I don't think it's
terribly likely, though.

4) Does anyone see a problem running about 13 amps through one
household outlet in a tree of several power strips?

This is probably in the grey zone. A lot of power strips are rather
cheap, and their internal wiring and contacts are designed for
"convenience" loads rather than high-current applications. If you
pull lots of amps through several of them together, you'll probably be
making the voltage-drop and heating problems worse.

I understand that many areas' electrical codes specifically forbid
"daisy chaining" power strips.

Should I increase my fire insurance coverage? :- )

I suggest that you revise your expectations, instead... limit your
circuit use and loads to what they are presently rated for.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

"Dave Platt"


At a guess, the external load may have dragged down the voltage at the
outlet far enough that the computer power supply's "line undervoltage"
circuit kicked in, and shut down the computer cleanly.

** Absolute ********.

Have you no idea of the source impedance at a domestic AC outlet ?

A load that dropped the voltage by more than 10% would trip the breaker
first.


..... Phil

On 9/12/2012 4:14 PM, Dallas wrote:

I’ve been putting the final touches on a new computer system with three
monitors and a 750 watt power supply. The printer is 600 watts, the
monitors are 170 watts, I have a TV on the other side of the wall
that’s 250 watts… add it all up to a usual load of about 15.3 amps. If
I turned on lights, amplifiers I can run the total up to 30.1 amps.

The circuit is 15 amps. :- (

And… I’d like to run all the computer equipment through one outlet so I
can unplug everything when the thunderstorms come.

So, I have a lot of questions:
1) First, why did the computer act like it tripped an overload in its
power supply, most of the load was outside of the computer? Why didn’t
the residential breaker trip instead?

2) Can a breaker cut the load for a second without mechanically
flipping to the off position?

3) I seem to remember some people just replacing the 15 amp with a 20
amp breaker when things get tight, is that a dangerous/stupid idea?
and illegal

4) Does anyone see a problem running about 13 amps through one
household outlet in a tree of several power strips?
I wouldn't


Should I increase my fire insurance coverage? :- )
Your fire insurance is based on the value of the stuff insured.
That's not affected by the load. Your carrier likely won't
insure you specifically against intentional overloads, more likely
will drop you. Stock up on weiners and stuff to make smores. ;-)

The power numbers on the name plate of electronic equipment may
bear little relationship to the actual power consumed under
normal conditions. And depending on the design of the equipment,
amps times volts can be significantly higher than watts.

If you really do have 30.1 amps and the 15A breaker doesn't trip, have it
fixed.

Call up the power company and ask them how to read the instantaneous
power from your utility meter. Count the revolutions/unit time
of the meter disk or the disk emulation on the LCD.
Use the formula they give you to calculate power consumption.
Do that with all your stuff on and again with all your stuff off.
Subtract the numbers.

Or you could buy a meter to tell you directly.
This is the most popular one.
https://www.google.com/products/cata...I&ved=0CC4QrQQ

The rule of thumb is to load a circuit no more than 80% of capacity. This means that for a 20 AMP circuit, the total load should not exceed 16Amps. Running more than that can cause the breaker to fail over time. This failure will show up as one of 2 options:
1) The breaker will trip with less than 20A total
2) The breaker won't trip EVER.

Both cases are cause for concern.

In regards to replacing a 15A breaker with a 20A one, this is a violation of the electrical code. The wires are sized based upon the load they will carry.

For a 15A circuit, the wire size is 14 guage. A 20 Circuit will use a 12. Placing a 20A breaker with 14G wire can cause hte wire to heat up and possible cause a fire. Don't do it.

Dan

The rule of thumb is to load a circuit no more than 80% of capacity.
This means that for a 20 AMP circuit, the total load should not exceed
16Amps.
Running more than that can cause the breaker to fail over time.

** ********.

This failure will show up as one of 2 options:

1) The breaker will trip with less than 20A total

** No hazard.


2) The breaker won't trip EVER.


** Insane crap.


In regards to replacing a 15A breaker with a 20A one, this is a
violation of the electrical code. The wires are sized based upon
the load they will carry.

** Plus a HUGE safety margin.

You ****ing, bull****ting tenth wit.


Placing a 20A breaker with 14G wire can cause hte wire to heat up and
possible cause a fire.


** Bull.





Dan

On 9/13/2012 4:39 AM, Phil Allison wrote:


The rule of thumb is to load a circuit no more than 80% of capacity.
This means that for a 20 AMP circuit, the total load should not exceed
16Amps.
Running more than that can cause the breaker to fail over time.

** ********.

This failure will show up as one of 2 options:

1) The breaker will trip with less than 20A total

** No hazard.


2) The breaker won't trip EVER.


** Insane crap.

I normally just ignore your ill-mannered ranting.
But in cases that involve legal issues or can result in personal harm,
your
mindless blather should be challenged.
We don't want any newbies reading this years from now to think
you have a clue and do something stupid based on your dismissal of
other's input.


In regards to replacing a 15A breaker with a 20A one, this is a
violation of the electrical code. The wires are sized based upon
the load they will carry.

** Plus a HUGE safety margin.

You ****ing, bull****ting tenth wit.


Placing a 20A breaker with 14G wire can cause hte wire to heat up and
possible cause a fire.


** Bull.





Dan

On Thu, 13 Sep 2012 10:28:54 +1000, "Phil Allison"
wrote:


"Dave Platt"


At a guess, the external load may have dragged down the voltage at the
outlet far enough that the computer power supply's "line undervoltage"
circuit kicked in, and shut down the computer cleanly.

** Absolute ********.

Have you no idea of the source impedance at a domestic AC outlet ?

A load that dropped the voltage by more than 10% would trip the breaker
first.


.... Phil

A demonstration of arrogance and stupicity in a single sentence -
quite typical for you.

NORMALLY a 15 amp outlet is wired with 14 guage copper, but many homes
built in the 60's and 70's used 12 guage aluminum wire. The
calculated voltage drop through a 100 ft run of 14 gauge copper NMC
cable carrying 15 amps would be 7.8 volts, aluminum would be 9.5
volts. HOWEVER, it is unlikely the wire runs directly from the
circuit breaker to the outlet in question, and we can't assume a
straight-line distance. Common wiring practice is to run the wire
back into the basement (or the attic) between outlets. If the attic,
each excursion would add 15 feet to the length. Also, each outlet
represents 2 (if using wire nuts) to 4 additional connections, each
increases the voltage drop slightly.

What is more, you ignore the realities of the typical (or even
premium) 'Made in China' power supply. They are often rated for an
input voltage from 100 to 240 volts. If you believe that is
rigorously tested, I have some Arizona oceanfront land to sell you.

PlainBill

In article ,
wrote:

A load that dropped the voltage by more than 10% would trip the breaker
first.

A demonstration of arrogance and stupicity in a single sentence -
quite typical for you.

NORMALLY a 15 amp outlet is wired with 14 guage copper, but many homes
built in the 60's and 70's used 12 guage aluminum wire. The
calculated voltage drop through a 100 ft run of 14 gauge copper NMC
cable carrying 15 amps would be 7.8 volts, aluminum would be 9.5
volts. HOWEVER, it is unlikely the wire runs directly from the
circuit breaker to the outlet in question, and we can't assume a
straight-line distance. Common wiring practice is to run the wire
back into the basement (or the attic) between outlets. If the attic,
each excursion would add 15 feet to the length. Also, each outlet
represents 2 (if using wire nuts) to 4 additional connections, each
increases the voltage drop slightly.

Also a factor: time. I've just looked at a couple of "current vs.
time-to-trip" curves for circuit breakers, and they seem to share some
common characteristics. Below a certain threshold (4x to 9x the
nominal rating), the breaker has a long (often *very* long) "time to
trip" - at 3x the nominal rating, the time-to-trip on these two is on
the order of 10 seconds. It isn't until you hit a higher-current
threshold that the breaker opens "instantaneously" (tens of
milliseconds or less).

Citations:

http://electrical-engineering-portal...current-curves

and Google on "circuit breaker trip curve" to find numerous other
example curves of the same general nature.

So, using the figures Bill cited above: if you drew 30 amps through a
100-foot 14-gauge aluminum-wire run, there would be 19 volts of
drop... and in the curves I'm seeing here, it looks as if the breaker
wouldn't open for over 20 seconds. That's more than a 10% drop in
nominal voltage, and this doesn't account for any voltage drop in the
outlet itself.

A current-draw surge of 45 amps would drop around 28 volts, and these
breakers wouldn't open for about 10 seconds (3x rated current draw).
This would put a nominal "120-volt" circuit down right around the
100-volt level.

I can tell you from personal experience, that if I start a 10"
hand-held circular saw (nominal draw about 6 amps I believe), and have
it plugged into a 15-amp circuit which shares an outlet with our den
and computer, the momentary surge of current draw when the motor
starts does *not* trip the breaker, but *does* cause the computer in
the den to abruptly power itself off - just as the original poster's
system did! I've had to learn not to use my power tools out by the
back shed (which has this shared circuit) when my wife is on-line...
the storm of "I lost the email I was writing" is just too painful to
bear :-)

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

wrote:


NORMALLY a 15 amp outlet is wired with 14 guage copper, but many homes
built in the 60's and 70's used 12 guage aluminum wire.
AIEeeeee! Not the aluminum wire thing again! The combination
of aluminum wire and outlets and other fixtures not specifically designed
for it has burned down a LOT of houses. Also, those ghastly spring-clip
outlets and switches that you poke the stripped wire into instead of
tightening a screw onto the wire are not reliable over time. If the OP
has aluminum wire, he should have it all ripped out and replaced as soon
as possible. Geez, the insurance companies ought to be paying people
to search out and replace that stuff! Probably not a whole lot of the
aluminum wire remains, it would have caused problems and quit working
if it didn't start a fire. That stuff has to be almost 50 years old by now.

Jon

"Phil Allison"

"Dave Platt"


At a guess, the external load may have dragged down the voltage at the
outlet far enough that the computer power supply's "line undervoltage"
circuit kicked in, and shut down the computer cleanly.

** Absolute ********.

Have you no idea of the source impedance at a domestic AC outlet ?

A load that dropped the voltage by more than 10% would trip the breaker
first.

A demonstration of arrogance and stupicity in a single sentence -
quite typical for you.


** It is a completely true statement.

( snip pile of irrelevant bull****)


What is more, you ignore the realities of the typical (or even
premium) 'Made in China' power supply. They are often rated for an
input voltage from 100 to 240 volts. If you believe that is
rigorously tested, I have some Arizona oceanfront land to sell you.


** Whatever, they will not drop out with only a 10% loss of line voltage.

You ****ing bull**** artist.


.... Phil

"mike"
Phil Allison wrote:


The rule of thumb is to load a circuit no more than 80% of capacity.
This means that for a 20 AMP circuit, the total load should not exceed
16Amps.
Running more than that can cause the breaker to fail over time.

** ********.

This failure will show up as one of 2 options:

1) The breaker will trip with less than 20A total

** No hazard.


2) The breaker won't trip EVER.


** Insane crap.

I normally just ignore your ill-mannered ranting.


** You would be far better of the actually READ it.

Cos it is all fact.


But in cases that involve legal issues or can result in personal harm,

** What absolute garbage.

When you have NOTHING to say - shut the **** up !!!!!!!!!

IDIOT !!

"Dave Platt"

So, using the figures Bill cited above:


** Test a REAL power outlet using a known load ( like an electric jug )
and measure the voltage drop at the pins.

For a 240V country, the source impedance is under 1 ohm so the drop at rated
( 10 amp) load is under 10 volts.

For a 120V country, the source impedance should be under 0.3 ohms, so a 15
amp load drops the voltage by no more than 4.5 volts.

In any case, it is the actual outlet voltage under load that counts and you
need to measure that too.

SMPS are usually rated for operation down to 85 or 90 VAC at FULL output.

The range of " 100V to 240V " simply means it covers the NOMINAL range of
all the world's AC supplies.



.... Phil

When you have NOTHING to say - shut the **** up !!!!!!!!!

My point exactly.

"mike = ****head"



When you have NOTHING to say - shut the **** up !!!!!!!!!

My point exactly.


** The only point you have is on top of your fat head !!!

You colossally stupid, over-snipping pile of sub human garbage.

FOAD !!

"Dave Platt = Radio Ham


Why didn't the residential breaker trip instead?

Residential circuit breakers are typically of the "thermal" type.


** WRONG !!!

They require some amount of time to react to an overload... the higher
the degree of overload, the slower they trip.


** WRONG !!!


"Magnetic" circuit breakers will trip very rapidly in the face of even
a short overload... but I believe these are rarely found in
residential applications.


** WRONG !!!

Domestic breakers are of the " thermal/magnetic" type - ie there are two
distinct mechanisms in the same unit.

The greater the overload, the FASTER they will operate !!!!

Most will trip after a few minutes at 20% above nominal amp rating.

At double the rated current ( 100% overload ) operation is within about 10
seconds, depending on previous history.

The magnetic trip is set way higher ( about 10 times ) the nominal amp
rating - it responds in less than half of a cycle to such overloads and
will even break the severe arc that results from a dead short on the
circuit.



..... Phil

On 9/13/2012 7:11 PM, Phil Allison wrote:
"mike = ****head"



When you have NOTHING to say - shut the **** up !!!!!!!!!

My point exactly.


** The only point you have is on top of your fat head !!!

You colossally stupid, over-snipping pile of sub human garbage.

FOAD !!







don't hold back.
Say how you really feel.

On Thu, 13 Sep 2012 16:03:02 -0500, Jon Elson
wrote:

wrote:


NORMALLY a 15 amp outlet is wired with 14 guage copper, but many homes
built in the 60's and 70's used 12 guage aluminum wire.
AIEeeeee! Not the aluminum wire thing again! The combination
of aluminum wire and outlets and other fixtures not specifically designed
for it has burned down a LOT of houses. Also, those ghastly spring-clip
outlets and switches that you poke the stripped wire into instead of
tightening a screw onto the wire are not reliable over time. If the OP
has aluminum wire, he should have it all ripped out and replaced as soon
as possible. Geez, the insurance companies ought to be paying people
to search out and replace that stuff! Probably not a whole lot of the
aluminum wire remains, it would have caused problems and quit working
if it didn't start a fire. That stuff has to be almost 50 years old by now.

Jon
I took this up with a professional electrician. He STRONGLY suggested
replacing the run from the power meter to the main circuit breaker
panel. He felt the rest of the wiring should be fine. As far as how
common aluminum wiring is, you are wildly optomistic. This house in
Arizona was built in 1969, my previous house in Florida was built in
1976. Both were wired with aluminum wire. So was virtually every
other tract home built in those states in that time period.

PlainBill

On Wednesday, September 12, 2012 4:14:59 PM UTC-7, Dallas wrote:
I’ve been putting the final touches on a new computer system with three

monitors and a 750 watt power supply. The printer is 600 watts, the

monitors are 170 watts, I have a TV on the other side of the wall

that’s 250 watts… add it all up to a usual load of about 15.3 amps. If

I turned on lights, amplifiers I can run the total up to 30.1 amps.



The circuit is 15 amps. :- (



And… I’d like to run all the computer equipment through one outlet so I

can unplug everything when the thunderstorms come.



So, I have a lot of questions:

1) First, why did the computer act like it tripped an overload in its

power supply, most of the load was outside of the computer? Why didn’t

the residential breaker trip instead?



2) Can a breaker cut the load for a second without mechanically

flipping to the off position?



3) I seem to remember some people just replacing the 15 amp with a 20

amp breaker when things get tight, is that a dangerous/stupid idea?



4) Does anyone see a problem running about 13 amps through one

household outlet in a tree of several power strips?



Should I increase my fire insurance coverage? :- )





--

Dallas

Go get a Kill-A-Watt and measure what it's really doing. I think you'll find your estimates are considerably off the mark. Just because you have a 750 Watt supply doesn't mean it uses 750. I have a 500 Watt supply on my PC. It idles around 110 and jumps to 200 when all 4 cores are at 100% Our 55" LED LCD TV runs 80 Watts

G²

"Dallas" wrote in message m...

I've been putting the final touches on a new computer system with three
monitors and a 750 watt power supply. The printer is 600 watts, the
monitors are 170 watts, I have a TV on the other side of the wall
that's 250 watts. add it all up to a usual load of about 15.3 amps. If
I turned on lights, amplifiers I can run the total up to 30.1 amps.

The circuit is 15 amps. :- (

And. I'd like to run all the computer equipment through one outlet so I
can unplug everything when the thunderstorms come.

So, I have a lot of questions:
1) First, why did the computer act like it tripped an overload in its
power supply, most of the load was outside of the computer? Why didn't
the residential breaker trip instead?

2) Can a breaker cut the load for a second without mechanically
flipping to the off position?

3) I seem to remember some people just replacing the 15 amp with a 20
amp breaker when things get tight, is that a dangerous/stupid idea?

4) Does anyone see a problem running about 13 amps through one
household outlet in a tree of several power strips?

Should I increase my fire insurance coverage? :- )


--
Dallas

Howdy doody Dallas. As a firm believer in M/F equal opportunity, I would recommend hiring a female electrician. Make it clear to her that she is expected to wear a regulation Nomex mini skirt and high heels (and that's all), is expected to climb up on the desk and check each the light receptacle voltage. And while she's up there, you can check her receptacle, too.

And you're welcome.

Bob

On Wed, 12 Sep 2012 17:25:03 -0700, (Dave Platt)
wrote:

In article ,
Dallas wrote:

So, I have a lot of questions:
1) First, why did the computer act like it tripped an overload in its
power supply, most of the load was outside of the computer?

At a guess, the external load may have dragged down the voltage at the
outlet far enough that the computer power supply's "line undervoltage"
circuit kicked in, and shut down the computer cleanly.

Somehow that doesn't sound reasonable.

Why didn’t
the residential breaker trip instead?

Residential circuit breakers are typically of the "thermal" type.
They require some amount of time to react to an overload... the higher
the degree of overload, the slower they trip.

Ummn, i think you meant: The higher the overload the faster they trip.
Every breaker has what is called an (i^2)*t curve. At threshold tripping
current it may take 4 hours to trip, at 10 X tripping current it must trip
within one second.

This allows a circuit to have a momentary over-current (e.g. a
refrigerator drawing a surge of current when it first starts up)
without repeatedly tripping the breaker.

"Magnetic" circuit breakers will trip very rapidly in the face of even
a short overload... but I believe these are rarely found in
residential applications.

2) Can a breaker cut the load for a second without mechanically
flipping to the off position?

Typically, no.

Well, if the circuit breaker trips it must move to the "tripped" position
and stay there until reset.

3) I seem to remember some people just replacing the 15 amp with a 20
amp breaker when things get tight, is that a dangerous/stupid idea?

It is quite possibly both dangerous and stupid, and likely illegal.
The circuit breaker is supposed to be selected to be below the upper
limit of what the circuit wiring and outlets can handle safely.

It is actually all three. If there is a fire and the insurance company
investigator finds such a circuit they won't pay a dime.

If you draw more current than the wiring and outlets are designed to
deliver, you can suffer excessive voltage drop in the wires (lights
dim, motors slow down, and devices with "low line voltage" shutdown
circuits will shut themselves off. The wires can overhead. Also (and
perhaps more of a problem), the outlets themselves can overheat.

Now, it is *possible* that the wiring and outlets in your house are
actually rated for higher amperage (or that the outlets could be
upgraded for this). If so, it *might* be possible for a licensed
electrician to confirm this, and then swap out the lower-rated outlets
and breaker to increase the branch current level. I don't think it's
terribly likely, though.

Very much agreed.

4) Does anyone see a problem running about 13 amps through one
household outlet in a tree of several power strips?

This is probably in the grey zone. A lot of power strips are rather
cheap, and their internal wiring and contacts are designed for
"convenience" loads rather than high-current applications. If you
pull lots of amps through several of them together, you'll probably be
making the voltage-drop and heating problems worse.

I understand that many areas' electrical codes specifically forbid
"daisy chaining" power strips.

Also true.

Should I increase my fire insurance coverage? :- )

I suggest that you revise your expectations, instead... limit your
circuit use and loads to what they are presently rated for.

Agreed.

On Thu, 13 Sep 2012 13:45:55 -0700, (Dave Platt)
wrote:

In article ,
wrote:

A load that dropped the voltage by more than 10% would trip the breaker
first.

A demonstration of arrogance and stupicity in a single sentence -
quite typical for you.

NORMALLY a 15 amp outlet is wired with 14 guage copper, but many homes
built in the 60's and 70's used 12 guage aluminum wire. The
calculated voltage drop through a 100 ft run of 14 gauge copper NMC
cable carrying 15 amps would be 7.8 volts, aluminum would be 9.5
volts. HOWEVER, it is unlikely the wire runs directly from the
circuit breaker to the outlet in question, and we can't assume a
straight-line distance. Common wiring practice is to run the wire
back into the basement (or the attic) between outlets. If the attic,
each excursion would add 15 feet to the length. Also, each outlet
represents 2 (if using wire nuts) to 4 additional connections, each
increases the voltage drop slightly.

Also a factor: time. I've just looked at a couple of "current vs.
time-to-trip" curves for circuit breakers, and they seem to share some
common characteristics. Below a certain threshold (4x to 9x the
nominal rating), the breaker has a long (often *very* long) "time to
trip" - at 3x the nominal rating, the time-to-trip on these two is on
the order of 10 seconds. It isn't until you hit a higher-current
threshold that the breaker opens "instantaneously" (tens of
milliseconds or less).

Citations:

http://electrical-engineering-portal...current-curves

and Google on "circuit breaker trip curve" to find numerous other
example curves of the same general nature.

So, using the figures Bill cited above: if you drew 30 amps through a
100-foot 14-gauge aluminum-wire run, there would be 19 volts of
drop... and in the curves I'm seeing here, it looks as if the breaker
wouldn't open for over 20 seconds. That's more than a 10% drop in
nominal voltage, and this doesn't account for any voltage drop in the
outlet itself.

A current-draw surge of 45 amps would drop around 28 volts, and these
breakers wouldn't open for about 10 seconds (3x rated current draw).
This would put a nominal "120-volt" circuit down right around the
100-volt level.

I can tell you from personal experience, that if I start a 10"
hand-held circular saw (nominal draw about 6 amps I believe), and have
it plugged into a 15-amp circuit which shares an outlet with our den
and computer, the momentary surge of current draw when the motor
starts does *not* trip the breaker, but *does* cause the computer in
the den to abruptly power itself off - just as the original poster's
system did! I've had to learn not to use my power tools out by the
back shed (which has this shared circuit) when my wife is on-line...
the storm of "I lost the email I was writing" is just too painful to
bear :-)

That is almost worth getting a UPS for the computer.

?-)

josephkk has brought this to us :
On Wed, 12 Sep 2012 17:25:03 -0700, (Dave Platt)
wrote:

In article ,
Dallas wrote:

So, I have a lot of questions:
1) First, why did the computer act like it tripped an overload in its
power supply, most of the load was outside of the computer?

At a guess, the external load may have dragged down the voltage at the
outlet far enough that the computer power supply's "line undervoltage"
circuit kicked in, and shut down the computer cleanly.

Somehow that doesn't sound reasonable.

Why didn’t
the residential breaker trip instead?

Residential circuit breakers are typically of the "thermal" type.
They require some amount of time to react to an overload... the higher
the degree of overload, the slower they trip.

Ummn, i think you meant: The higher the overload the faster they trip.
Every breaker has what is called an (i^2)*t curve. At threshold tripping
current it may take 4 hours to trip, at 10 X tripping current it must trip
within one second.

This allows a circuit to have a momentary over-current (e.g. a
refrigerator drawing a surge of current when it first starts up)
without repeatedly tripping the breaker.

"Magnetic" circuit breakers will trip very rapidly in the face of even
a short overload... but I believe these are rarely found in
residential applications.

2) Can a breaker cut the load for a second without mechanically
flipping to the off position?

Typically, no.

Well, if the circuit breaker trips it must move to the "tripped" position
and stay there until reset.

3) I seem to remember some people just replacing the 15 amp with a 20
amp breaker when things get tight, is that a dangerous/stupid idea?

It is quite possibly both dangerous and stupid, and likely illegal.
The circuit breaker is supposed to be selected to be below the upper
limit of what the circuit wiring and outlets can handle safely.

It is actually all three. If there is a fire and the insurance company
investigator finds such a circuit they won't pay a dime.

If you draw more current than the wiring and outlets are designed to
deliver, you can suffer excessive voltage drop in the wires (lights
dim, motors slow down, and devices with "low line voltage" shutdown
circuits will shut themselves off. The wires can overhead. Also (and
perhaps more of a problem), the outlets themselves can overheat.

Now, it is *possible* that the wiring and outlets in your house are
actually rated for higher amperage (or that the outlets could be
upgraded for this). If so, it *might* be possible for a licensed
electrician to confirm this, and then swap out the lower-rated outlets
and breaker to increase the branch current level. I don't think it's
terribly likely, though.

Very much agreed.

4) Does anyone see a problem running about 13 amps through one
household outlet in a tree of several power strips?

This is probably in the grey zone. A lot of power strips are rather
cheap, and their internal wiring and contacts are designed for
"convenience" loads rather than high-current applications. If you
pull lots of amps through several of them together, you'll probably be
making the voltage-drop and heating problems worse.

I understand that many areas' electrical codes specifically forbid
"daisy chaining" power strips.

Also true.
In Australia Power strips are generally fitted with a breaker so the
first strip governs the total load (10 amps)on a daisy chain and so
ensures (goes a long way) no overload occurs.

I think this has been a requirement for may years now.

Should I increase my fire insurance coverage? :- )

I suggest that you revise your expectations, instead... limit your
circuit use and loads to what they are presently rated for.

Agreed.

--
John G