Topic: How much electricity can my wall outlet handle? (Read 39403 times)

Breakers arn't really designed to trip when you only just exceed the ratings of your wires or sockets, they're designed to trip to prevent catastrophic events like fires caused by short circuits. If you really want to impose a hard limit to the power drawn through a circuit, then add some fast-blow fuses in series with the load.


http://en.wikipedia.org/wiki/Circuit_breaker

One reason why normal circuit breakers can't instantaneously trip precisely at the maximum continuous load rating of cables and sockets/plugs is because some types of loads (especially refrigeration pumps/compressors) can momentarily exceed (usually for <<1 second) those ratings.

In my country (Australia) all power boards must have overload protection at 2400 VA to prevent fires due to overload. These overload protection devices will 'activate' much earlier than a circuit breaker ever will.

If you are relying on your circuit breakers to protect you from a wall socket / wall cable fire then are in for a shock...

Not all wall outlets are equal.  Depending on how house is wired can very greatly.  You will know its to much if breakers start tripping.

I'm in the US but I run my computer off 240v. Most power supplies today can handle multiple voltages and frequencies. If you have a dryer outlet or any 240v receptacle you can get a standard pc power cable that will plug into a 240v socket. Using 240v effectively cuts your amp draw in half so at 20 amps thats ~4800watts or 30 amps ~7200w.

He typo'd. Me meant 1800VA. He missed a 0.

Also, some people might wonder what the difference is between VA and watts. An AC circuit is a sine wave. When you measure the volts of some AC with a multimeter, the displayed volts is the peak voltage. The voltage isn't always 120v. It goes up and down in a regular fashion 60 (or 50) times a second, like a sine wave. Now, take a device thats 1500 watts (12.5 amps @ 120 volts) and tries to pull a significant amount of power while the sine wave is not at or near a peak (say when the wave is at 60 volts instead of 120), it will draw more current to compensate (twice as much in this scenario). So while the power consumed will continue to draw 1500 watts, it will in fact be drawing 25 amps, or 3000 VA (!), which will easily trip a breaker, or melt wire insulation if for some reason you aren't using a breaker. The way this is gotten around for AC to DC, like computer power supplies, is active PFC. It aligns power draw with the peaks of voltage, so your VA will always be very close to your watts.

Kill-a-watts measure both watts and VA. Try plugging in an old, budget, non-PFC computer power supply and load it up and compare watts to VA, and do the same with a newer power supply with active PFC.

Yes, you should be fine pulling everything from the one outlet. The breaker is made to trip before the outlet and wiring become a hazard. However, if you have old electrical, that may be a problem. I was in this guys basement, and the house had some poor electric from the 50s or something. The wiring consisted of two wires, as thin as cheap earphone wires, for polarity. No ground or anything. And the tops of these wires were burnt off with obvious evidence of the wires catching fire multiple times. It's amazing this family didn't burn down their house years ago. I think generally speaking, if you house was built in the past 30 years, everything should be fine.

What you should be careful about it any extension cords or surge protectors you have.

not always with alternating current you have to take the power factor into account 

Wait, so the circuit is rated for 1800W, but each outlet is only rated for 180W? That doesn't seem right...

For the record, volts X amps = watts

I am actually a licensed electrician, you are somewhat correct but what you are actually pulling from the outlet is amperage at a 120v. Generally a residential wall outlet is rated for 180VA for calculation purposes. VA is volts*amps. Max total for each 15a circuit is 1800va. This means you can pull up to 15a at 120v before the breaker trips on the whole circuit. The breaker is mainly to protect the wiring from overheating and possibly causing a fire.

So by this calucation you could use 1800 watts on each circuit, but you have to consider the fact that you will be operating a continuous load. In which case you multiply your load by 125%. Also there are variations in actual voltages at different outlets. If your specific outlets is only delivering 108 volts this will increase the amperage and heat pulled. If you want to load this outlet to the maximum safest load, get a meter and check the voltage on it several times during the day in different scenarios (appliances on and off, ac or heat running or not,TV's etc.)
Get the average voltage. Add up the total load of your equipment, add 25% and that should be a safe bet. Also know that you are ccalculating the load for the 15a circuit not the one outlet. If there are other outlets on the same circuit whatever is plugged into them needs to be calculated in the total load. You should also spread the load out over several outlets on the same circuit if possible and and check the max load on the actual receptacle.

Sounds like you've got it pretty figured out. The only thing I can think of: that 15A rating is for the whole circuit, NOT just the one plug. You can' plug 10 computers that all use 300W into different outlets, and you'd still blow the breaker reeeeal quick.

You seem very unsure about it all, I would recommend you have an electrician look at it. While we could tell you the theoretical maximum of your plugs/wiring as per whatever standards exist in Canada, that does not mean that your plugs/wiring currently meet that standard and are in good condition.

I live in Canada, the ratings are: 120V from the socket, with the wiring in the wall rated at probably 15A.

Does this mean that I can safely pull 1440W (.80 rule) from the wall, or is this pushing it?

My Kill-A-Watt is registering around 1100W from the wall. How much more electricity can I safely pull at the socket for an extended duration?