Half a croissant, on a plate, with a sign in front of it saying '50c'
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High Power Kitchen Appliance Switch for Single Outlet

Switches appliances to keep below circuit breaker's rating
  [vote for,

I have a microwave oven and a toaster-oven that can plug into only one outlet (each USA power "outlet" is dual sockets, so it can have up to two plugs put into it). When operated together, they pull more current that the circuit breaker is rated for, and it opens the circuit.

This idea is for a box with a power cord that plugs into the wall, and several (single-socket) outlets on it that other things (especially high-power appliances) can be plugged into. Each outlet is switchable on or off under microcontroller control, and the microcontroller senses the current going through each outlet. When the total current drawn exceeds that rated for the power circuit (the toaster-oven is on and I turn on the microwave oven), the microcontroller will switch off one or more of the outlets so that the current drops back below the maximum for the circuit.

Each outlet will have a "priority" so that if the the maximum power is exceeded, the lowest priority socket will be turned off first, and if there is still an overload (this could be calculated before the first is switched off so several outlets may be switched off simultaneously), the next lowest priority socket is also switched off, and so on until the power is again below the maximum for the circuit.

This way, I could be heating something "long-term" (that takes, say, ten minutes) in the toaster oven, then put a cup of water in the microwave and run it for two minutes to make instant coffee or hot tea. When the current from the microwave is detected, the toaster oven will be immediately switched off, then when the current to the microwave goes back to the very low value that just keeps the clock and control circuitry going, this will be sensed and the toaster oven will be turned back on.

I'll get the hot coffee/tea in the expected time, and the toaster oven's food will only be delayed a couple of minutes, and I won't have to turn one off to run the other (or unplug one to plug in the other - I actually have a small refrigerator plugged into the second socket of the wall outlet).

I have the electrical and microprocessor programming knowledge to make a prototype, but the thought of dealing with regulatory and safety agencies, ESPECIALLY for something that would allow or depend on pulling excess current from an outlet (even if it's only for a single cycle), prevents me from attempting a commercial product.

benbradley, Aug 21 2014


       A bunch of auto-resetting RCDs will do some of what you want, but I'm not sure about having a "hierarchy". Perhaps scale the break and/or reset currents?
neutrinos_shadow, Aug 21 2014

       Try 230 volts, or 3 phase. Don't bother with Japanese 100V, can't have washing machine/aircon/toaster on at the same time...
not_morrison_rm, Aug 21 2014

       It's funny reading this idea because your set-up and practices are just like mine. I have toaster, microwave and small fridge. And I had a problem with these tripping the breaker. Also I use the same routine of preparing something in the toaster and a hot drink in the microwave.
rcarty, Aug 21 2014

       Just pull out the RCD/breaker and put in a bigger one. Just kidding, this might set fire to your house, although it's unlikely. You'd still retain RCD protection...   

       More realistically, get an electrician to upgrade the outlet to two independent circuits. The wires are already there, so the job is a lot easier - they'll use the existing wires to pull a string through, then use that string to pull two sets of wires back through the wallspace. Put another RCD/breaker into the board, and connect. Bingo. Probably not even an hour's work, about 10 bucks worth of wire, and a $10 RCD.
Custardguts, Aug 21 2014

       ^ - the two outlets are supposed to be the two phases, but electricians usually don't bother because it's cheaper to just drop one circuit in.   

       In the meantime you could plug something into the stove's outlet(s): it's on a totally different breaker.
FlyingToaster, Aug 21 2014

       //toaster, microwave and small fridge. And I had a problem with these tripping the breaker.   

       Ha! 230 volts sneers at a mere three domestic appliances....call that a load? Kids stuff....I didn't even know what a trip switch looked like until I left the 230 volts area...   

       If the Manhattan Project had been on 230v then Hiroshima would have been a smoking crater in 1943.   

       Goes back to reading The Telegraph...
not_morrison_rm, Aug 21 2014

       American houses do HAVE some proper electricity. You sort of need it to run big AC units or the clothes driers you inexplicably use despite the Venus-like temperatures outside.   

       Just get an electrician to run more 220V circuits everywhere. Or ask them to install British grade electrics. Then marvel as your 3000W electric kettle boils water in less than a week, or your vacuum cleaner does more than make an annoying noise.   

       I'm for a worldwide 415V 3-phase standard.
bs0u0155, Aug 21 2014

       You didn't say what the amperage rating was, of the circuit breaker that trips. If it is a 20Amp breaker, that means the wire going from the breaker to the outlet is supposed to be at least 12 gauge. If you wanted to replace the breaker, you would have to open enough of the breaker-box that you could examine the wire --CAREFULLY!-- and verify that it is 12 gauge.   

       The point of this anno relates to a "safety margin" associated with 12-gauge wire and 20-amp breakers. If the distance from the breaker to the outlet is less than 15 meters, you can PROBABLY safely upgrade to a 25-Amp breaker for that 12-gauge wire, if you can find a breaker having that value (electrical-supply house). But I can't promise this will solve your microwave and toaster problem; they still might be drawing too much.
Vernon, Aug 21 2014

       Having lived in the US for a few years, I am amazed how primitive at how primitive US electrical systems are. Our house there had 110V sockets everywhere and a single 220V socket for the tumble dryer. It would be unthinkable to have a kitchen in the UK where you couldn't plug in two things at the same time.

Having said that, I do have the same problem at home of being unable to plug in two devices on the same circuit, but only because those two devices are 12.5kW each.
hippo, Aug 21 2014

       //Having lived in the US for a few years, I am amazed how primitive at how primitive US electrical systems are//   

       My lights dim when I plug the iron in. My vacuum still works when I accidentally pull the plug half out with half an inch of exposed pins. I inexplicably have a plug socket controlled by a light switch. Ground/Earth is OPTIONAL. My work has just turned off the building's air conditioning because they have a deal with the power company to do so when the local grid is stressed. It's nuts.   

       I do like 60Hz though, can't see the 60Hz flicker out of the corner of my eye like I can with 50Hz.   

       I reiterate my call for a global 415V 3 phase standard. Then we can all have 12.5kW hairdryers.
bs0u0155, Aug 21 2014

       Luckily they're not kitchen appliances - they're ceramics kilns, each capable of heating a good number of pottery objects up to about 1200°C
hippo, Aug 21 2014

       //objects up to about 1200°C//   

       Like I said, hairdryers.
bs0u0155, Aug 21 2014

       //Having lived in the US for a few years, I am amazed how primitive at how primitive US electrical systems are//   

       I would agree. Aside from the limitation of running a low-voltage system, the hardware is flimsy and does not inspire confidence.   

       In Europe, they have equally flimsy electrical hardware, but running at a proper voltage (220VAC).   

       Only the Brits seem to have got it right, if you ask me. A useful voltage; and plugs, sockets and switches that look like they were made for it.
MaxwellBuchanan, Aug 21 2014

       being AC it'll be WAY more complicated than that no? there's lots of things ending in"-ance" to consider...
bs0u0155, Aug 21 2014

       415V 3 phase would be just the ticket to produce a VERY functional hairdryer.
bs0u0155, Aug 21 2014

       That's quite a dwell time between account establishment and first idea. Welcome to the Halfbakery.
normzone, Aug 21 2014

       //60Hz flicker out of the corner of my eye like I can with 50Hz.   

       If you want the option of 50/60Hz then just move to Japan....back in the past no one ever thought that there'd be a national grid...   

       "The frequency of electric current is 50 Hertz in Eastern Japan (including Tokyo, Yokohama, Tohoku, Hokkaido) and 60 Hertz in Western Japan (including Nagoya, Osaka, Kyoto, Hiroshima, Shikoku, Kyushu)"   

       and so it remains to this day....
not_morrison_rm, Aug 21 2014


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