Overload an electrical outlet?

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.

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.

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.

Typically, no.

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.

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.

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

"Dave Platt"

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

and illegal

I wouldn't

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.

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 failu= re will show up as one of 2 options:

Both cases are cause for concern.

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

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 poss= ible cause a fire. Don't do it.

Dan

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

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:

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

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

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 :-)

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

Cos it is all fact.

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

IDIOT !!

"Dave Platt"

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

My point exactly.

"Dave Platt = Radio Ham

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

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

PlainBill

If

Go get a Kill-A-Watt and measure what it's really doing. I think you'll fin= d 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. I= t idles around 110 and jumps to 200 when all 4 cores are at 100% Our 55" LE= D LCD TV runs

three

If

didn't

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

Somehow that doesn't sound reasonable.

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.

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

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.

Very much agreed.

Also true.

Agreed.

breaker=20

That is almost worth getting a UPS for the computer.

?-)

josephkk has brought this to us :

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.