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Today, I got a new toaster oven. When it's heating, my kitchen lights (plugged into an adjacent outlet) flicker/pulse.

What can I do to reduce the flickering?

If I get a power conditioner, can I put it on the power supply to the toaster oven, so that the appliance doesn't impact any other outlets in the household? It looks like power conditioners are usually intended to be used on the devices you want to shield, rather than on the device that's causing the problem; does it work both ways?

I'm in Canada, so my mains power is 120 V at 60 Hz.

Edit - more details:

  • New toaster oven: Breville BOV800XL "Smart Convection Oven", 1800W
  • Old toaster oven (no flickering problem): Hamilton Beach, convection, 1440W
  • Microwave on same outlet (no flickering problem): Panasonic Inverter, 1100W output, 1200W input

The new toaster oven doesn't exhibit the flickering problem if I'm toasting; only if it's heating on "bake" mode (both when the convection fan is on and off). The lights dim when I turn the toaster oven on any mode, but on "toast" they don't flicker; they just dim and stay dim until the toaster oven shuts off.

The flickering happens around 8 Hz (but it's hard to tell for sure). I put a Kill-a-Watt meter on the lights (which were turned on), and got the following readings, but it only updates the display once per second:

  • Toaster off: 118.7 .. 119.2 V
  • Toaster on "toast": 117.1 .. 117.6 V
  • Toaster on "bake": 117.2 .. 117.4 V, flickers

The light fixture is mounted above the counter, not the main kitchen light fixture; it has three sockets rated for 50W each and a single on/off power switch (no dimmer control). I don't know what kind of bulbs they contain but I think they're incandescent:

Bulb photo 1 Bulb photo 2

It appears that no other lights are affected (ie. the overhead lights, the range hood light, or a fluorescent fixture above the sink).

I guess the toaster oven is doing some PWM thing when it's on bake? I don't know for sure, but the flickering is very distracting.

This is an old house (100 years this year, I think) but the wiring was updated within the last decade, I believe. I'm renting so it's unfeasible for me to do anything about the wiring and setup (but I suppose I could run extension cords).

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What kind of lights? Incandescent? Fluorescent? LED? Dimmable or not? What make and model of toaster oven? –  Kaz May 30 at 21:29
    
@Kaz, good points. I've added more details. –  mrb May 30 at 22:07
    
Baking requires temperature regulation. If the oven is doing some PWM frequency, the flicker could just be the result of intermodulation ("beats") between the light's 120 Hz flicker (that you normally don't perceive) and the pulsating frequency used by the oven (say it was 128 Hz: 128 - 120 - 8 Hz.) –  Kaz May 30 at 22:38
    
Is the outlet in good (or better) condition? If it is old and the outlet contacts do not firmly grasp the prongs, it should be replaced. –  wallyk May 31 at 3:25

4 Answers 4

The problem isn't within the toaster, and adding a "power conditioner" wouldn't help. It's simply drawing a lot of power from the outlet, and the wiring impedance between the outlet and the distribution panel is causing the voltage at the outlet to drop a bit.

In general, the lighting circuits and the countertop appliance circuits should be on separate breakers to begin with, so that an appliance fault won't leave you in the dark with a potentially dangerous situation (hot and/or spinning objects).

You should try to work out which outlets in your kitchen are on which circuits, and operate the toaster on a separate circuit from the one your lights are plugged into.

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That's reasonable. I have a main kitchen light on a separate circuit; apparently the only outlet affected is the one next to the toaster. I'm just curious as to why this never happened with my microwave or my old toaster (sorry, I only just added more details to my question). It also doesn't happen on all modes on the toaster; maybe it's doing something special on "bake". –  mrb May 30 at 22:10
    
I would think it's caused by the resistance of the wires, and that toaster and bulbs somewhere share wiring. In what way could impedance play a role? –  Volker Siegel May 31 at 6:46
    
@VolkerSiegel: Impedance is simply a more general term, which includes both resistance and reactance. Yes, in this case, the resistance is the most significant factor. –  Dave Tweed May 31 at 10:50

I suggest you check the power cord of the toaster over for heat (cord, plug, wall outlet). I would also suggest you check the circuit panel for heat using some kind of remote sensing device like an infrared thermometer gun (or in worst-case visually examining for signs of excessive heat like melting of insulation).

I had a similar problem and it turned out that the connection at the circuit panel wasn't correct. Turning on a high-impedance appliance caused arcing in the circuit breaker and actually melted the insulation on the wire.

The arcing caused the flickering in the lights.

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In Canada and the US, kitchen outlets are wired so that the top plugs on adjacent outlets are circuit A, and the bottom plugs are circuit B. Yes, it's weird (and a royal pain for the people actually doing the wiring) but that explains why the top and bottom circuits are not behaving the same.

The toaster oven draws a lot of power, but it should not dim a simple lighting circuit that much. You may have a serious electrical problem, and unless you are confident enough to do your own work, call an electrician to pull the outlets and the breaker. I won't supply instructions - if you don't already know how to do this, call someone. Do this soon, like today, or at least before your house burns down.

Moving plugs around might "make the problem go away" but if you have corroded connections it will just make the problem less obvious as it slowly gets worse.

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2  
"In Canada and the US, kitchen outlets are wired so that the top plugs on adjacent outlets are circuit A, and the bottom plugs are circuit B."......... This is not at all true of the US. Or at least it is extremely uncommon. –  Speedy Petey May 31 at 12:17
    
What you have written may be a common way to wire them, but it is not always the case. ( I don't think I have ever come across a house wired that way. ) –  Brad Gilbert Jun 1 at 16:25

I suggest you have an electrician install some dedicated wiring for your kitchen. You may be creating a fire hazard pulling that kind of current through old wiring.

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