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I have an extension lead from the main socket in my home office. Attached is a fridge (drinks fridge but not a mini fridge - 80L). Then I have another extension attached to that one that contains all of my computer set up (2 monitors, Mac charger, PS4 and a light).

When ever the compressor for the fridge starts up, one of my monitors loses power for a second and then comes back on. Same happens when the compressor of the fridge shuts off. It used to happen on the other monitor, but now happens on this one leading me to believe that it's a certain plug in the extension that has the issue since I recently moved things around.

Is this something to worry about? Is this a surge that is causing my monitor to lose power?

I've had nothing but issues with the fridge since I got it. It's very loud when the compressor is on and when it turns off, it makes quite the sound (not a bang, but a loud click and rumble).

At the time of writing, the monitor didn't actually come back on. However it did come back on manually. But this time, the signal was lost. Replugging the display port back in to the mac solved this issue.

Further notes:

This has only been happening for the past month or so (fridge is ~4 months old)

This is the second fridge, the first had to be sent back and replaced as it was far too loud and must have had an issue

The internal light stopped working after about 2 weeks

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  • What are the power requirements of all the things you have on this circuit? My guess is that you are exceeding the capacity of the circuit and compounding the problem with all these extension cords.
    – jwh20
    Jul 13, 2021 at 12:14
  • Check your fridge's labeling for an LRA value because this will tell you the startup amperage requirement for the fridge. If the LRA plus all of your devices exceeds your breaker size then you need to get your setup onto a different circuit. You should also get a multimeter and check if your fridge is causing a voltage drop on your circuit when the compressor starts up. If it does then it's called a brown-out and that is really, really bad for the other electronics on that circuit.
    – MonkeyZeus
    Jul 13, 2021 at 13:13
  • It is just your fridge telling you to turn off the computer and start cooking supper.
    – John Canon
    Jul 13, 2021 at 13:56
  • I would check the connections I have seen this exact problems dozens of times in the last year alone. If the breaker is not tripping you shouldn’t have enough voltage drop in a residential setup to cause the problem. Electrical noise can do it but things changed when you moved plugs around this points to bad or weak connections, ups will solve the problems but they are masking a potential hazard in my opinion.
    – Ed Beal
    Jul 13, 2021 at 16:01
  • I would recommend isolating computing equipment from heavy (or even moderate) motor loads in all situations. It's just asking for computer trouble. Be happy it's a monitor going, not the computer itself - if the computer starts losing power, at a best you'd likely be losing data, at worst, you could lose the whole computer.
    – FreeMan
    Jul 13, 2021 at 17:21

3 Answers 3

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This problem is not uncommon even with good wiring because motor circuits create a large amount of electrical noise on both startup and when they turn off.

It is recommended to not have sensitive electronic equipment on the same circuit for this reason.

There are things that can make the problem worse, specifically weak electrical connections such as back stabs the small contact area of a backstab creates a high resistance connection so when the motor is starting and drawing it’s max current the voltage drops causing the electronics to drop out.

Making all connections screw or pigtail type may eliminate the problem.

I have had a fair amount of success in removing backstabs and pig tailing connections not 100% problem solved but a high % that fixing the connections worked.

In a few cases a new circuit was needed to eliminate the problem but fixing connections may work and it only cost a little time in most cases.

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    I would recommend a UPS for computer equipment anyway, whether or not it stays on that circuit. An APC 450 usually runs under $50.
    – rtaft
    Jul 13, 2021 at 14:09
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    Agree completely with @rtaft I was going to make the same suggestion. A UPS will not only smooth out the power, it will also provide some time (not long), to properly shut down your equipment in the event of a power outage. Some UPSs communicate with the computer to gracefully start shutting things down if the power fails.
    – George Anderson
    Jul 13, 2021 at 14:33
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    I'd also add that if the computer uses a lot of power (high end graphics card / gaming rigs) to get something a lot bigger than a 450 as they beep like crazy if you draw too much power. They also beep when they engage the backup, but you can turn that feature off.
    – rtaft
    Jul 13, 2021 at 14:39
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It's your extension leads

There is an epidemic of cheap, counterfeit extension leads in the UK. BigClive and John Ward do regular teardown videos on them, and they are cringe-worthy.

Check your leads for a BSI quality label. Failing that, TUV, or at least UL, CSA, ETL or any NRTL, really. (BSI is a NRTL).

I'm betting you find nothing but a big CE label. CE is a "self-certification". The EU government doesn't even check it and has no enforcement authority, unless the manufacturer or importer has bricks-and-mortar presence inside the EU. As such, mail-order (and flea markets and informal junk shops) have become a superhighway for cheapazoid leads with dangerously thin wires.

Refrigerators are very light loads when running, but being a motor drive, they have an enormous startup current. The thin wires in your cheap extension leads are combining with that startup current (and Ohm's Law) to dip voltage so low the monitor power supply quits.

Get extension leads with a BSI certification that are actually rated for large appliances (e.g. have 1.5-2.5 mm2 wires in them).

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A top-quality new refrigerator, even full-size (actually, especially full-size, as the manufacturers can afford to spend a few $ extra on better quality compressor, etc. because perception is "bigger" = "more expensive" even though the only part that really scales up is the "box"), should not have this problem.

The standard electrician & manufacturer recommendation is: Put your computer equipment on a dedicated circuit and your refrigerator on a dedicated circuit (or at least a circuit with no sensitive equipment and/or large continuous current draw equipment). The reality, of course, is that due to a variety of factors many of us don't have that option. (My main computer (basement) is on the same circuit as: basement "extra" refrigerator & freezer, some of the basement lights, some lights and receptacles in 2 bedrooms, kitchen light, cooktop exhaust fan).

The problem could be simple "interference" or "noise". But my hunch (based on the noise and other problems you have noted, and the general quality of small refrigerators) is that the refrigerator draws so much power when it starts up the compressor that it causes a temporary voltage dip on the circuit that is enough to cause problems. That is actually quite common - when my laser printer starts printing my UPS will usually cycle on because of the voltage drop. Your problem monitor happens to be just sensitive enough that it treats the drop as an outage and turns itself off. Depending on the exact voltage drop & duration, it either turns back on automatically or requires a manual restart.

A UPS is definitely a good solution. Swapping for a different model of monitor may help, but no guarantee. I'd be more inclined to swapping the refrigerator since the induced monitor problem is not your only complaint about the refrigerator. But other than scouring reviews to compare and see which refrigerators are "better", that is no guarantee either.

If you own your home rather than rent, consider getting an electrician in to install an additional circuit. But if this is a rental then that would have to go through your landlord and I have a feeling they won't want to spend the money. The cost for an additional circuit can be very low (perhaps as little as $50 in parts + 1 hour of labor - but possibly plus permits (depending on location) and getting an electrician (if you don't DIY) is not always so easy for a small job...YMMV) to very high (if there are no breaker spaces available or if it is hard to run a new cable from the panel to the point of use).

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    The reason prices are off topic is where in the world can you get a new circuit for 50$ my state just the minor permit fee is that , add a breaker and some wire and even a diy job will cost 100$ and to have it done 5x that amount or more depending if you can get an electrician to do it, we have been booked for months.
    – Ed Beal
    Jul 13, 2021 at 15:55
  • @EdBeal Added some clarification. I am throwing in a $ amount to indicate that there are situations where "add a separate circuit" is really minimal and that other times it isn't. When I redid my kitchen years ago (I hired out the electrical and plumbing to pros but I did the rest myself +relatives) the electrical & plumbing were relatively easy because panels & gas & water pipes right below the kitchen in unfinished space. But I know other people where the costs were MUCH higher. Someone starting out with this may have no clue that "add a circuit" is not necessarily a super-expensive thing.
    – manassehkatz-Moving 2 Codidact
    Jul 13, 2021 at 16:52

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