Hi Saviors on the internet,

Recently, I have been having this issue within my apartment is that when I turn on/off my fan there will be a power surge within my house and sometimes causes my internet to drop.

It doesn't just stop there when I alternate between the different fan speed, it can also cause my internet to drop off. I believe it might be due to the power surge within my house, however, I am not quite sure what might be causing it.

I believe it's not due to my Desktop's multi-plug, as if it was the power surge due to that my desktop would turn off by itself and restarts. However, the desktop is perfectly fine and only the internet is affected.

Does anyone know the issue to this?

Thank you for your time and concern guys.

  • 1
    Are your internet devices (modem, router, etc.) on the same circuit as the fan? (i.e. does the same breaker turn off power to both of them?) If so, simply moving your internet devices to a different circuit might be enough to solve the problem.
    – Nate S.
    Jun 17, 2019 at 17:49
  • 1
    Yes, everything is going to the same breaker within this apartment. There are not spare circuit currently. It's like the main source comes into the apartment and parallel out I believe.
    – Eric L
    Jun 17, 2019 at 18:41
  • Your apartment only has a single circuit? That's unfortunate (and not to code in much of the world, but since you haven't given a location, perhaps that's normal where you live.) I'll write up an answer with some other suggestions.
    – Nate S.
    Jun 17, 2019 at 19:52
  • You mention internet dropping off & modem/router. Is the unit all-in-one? Do this simple test, If you have a cell phone or tv or something else on the internet, unplug the computer multiplug completely from the wall. Try your fan test with the modem right where it is. Does it cutout? Presumably yes. So if so, move the modem/router to where the computer multiplug was plugged in, try the same test again!!!! then report back here. Presumably, it still is an issue. But if it isn't, we can help a little further
    – noybman
    Jun 17, 2019 at 20:40
  • Is the modem/router wired or wireless? What vintage is the ceiling fan, and does it use pull chains, a remote, or a wall control for speed control? Jun 17, 2019 at 23:13

3 Answers 3


It would be useful if you could explain how you concluded that "when I turn on/off my fan" then "there will be a power surge within my house" - do you mean that changing the fan speed and/or on/off state causes lights to flicker? That would be very odd, as "light flickering" is usually associated with high-current changes (like a microwave oven or air conditioner turning on), and normal box fans are in the 100 watt range (i.e. low power).

Your desktop not powering off at the same time may not be a useful bit of data: PC power supplies have a "hold up" capacity that could be many dozens of milliseconds long ("hold up" is "supplies power to the PC even though the wall power has failed"). This is long enough that the PC can ride out the power "excursion".

The other thing to know is that in the USA at least (can't speak for where you are), residential power comes into the house on two 180-degrees-out-of-phase legs, each 120 volts above ground (neutral). This is so that we can allow both 120V (one leg to ground) and 240V (potential between the legs) appliances. If your fan is on one leg, the Internet router/modem is on the same leg, and the desktop is on the other leg, then power fluctuations caused by the fan can affect the router/modem (on the same power leg) while the desktop is unaware (different power leg).

Are there lights on the router/modem? Can you tell if it is rebooting or re-connecting when the fan causes the Internet outage? That would at least explain what is happening, if not exactly why.

Your simplest solution might be to replace the fan to see if the flickering problem goes away. The second-most simple solution is to get a UPS for the router/modem and desktop.

You may need to get your landlord to have an electrician investigate the flickering, as that is not normal to have a fan cause it.

  • A box fan that's rated for 100W nominal may well need ten times that or more when it's first starting up -- all electric motors do. This is known as inrush current, and it could indeed cause a momentary brownout on a circuit that's already heavily loaded, as it sounds like OP's is.
    – Nate S.
    Jun 17, 2019 at 20:11
  • @Russell, what I meant was when I turn on my ceiling fan the modem/router connection gets cut off momentarily. Wherelse everything else within the house works perfectly fine. The reason as to why I mentioned my desktop is because of everything within this apartment is connected to a single output source into the circuit breaker before being parallel out to different part of the apartment. Hence, the modem/router is connected to another power output source and the PC is connected to another source. The PC does not suffer from anything elsewhere the Modem/Router suffers a "cutoff".
    – Eric L
    Jun 17, 2019 at 20:17
  • @Russell, the lights on the Modem/Router doesn't change. However, it's like a 1-2 seconds cut off and then it will be back to normal. Which leads to my question regarding power surge, because if it's a power surge I'm thinking perhaps a surge protector might solve the problem.
    – Eric L
    Jun 17, 2019 at 20:20
  • A router reboot typically takes a lot longer than 1-2 seconds (like 30s or more), so this sounds less like the router rebooted from brownout (what Nate Strickland is suggesting), and more like electrical noise causing the modem to lose sync and having to renegotiate. Do you know what physical connection your internet modem uses (on the WAN side)? Typical answers are: DSL (looks like telephone wire), cable TV (coax), broadband over powerline (weird wall-wart thing).
    – Russell
    Jun 17, 2019 at 20:44

This is a pretty common problem with high-powered electric motors, such as the one in your fan. Inside the fan's motor, there are coils of wire which will create a magnetic field when you push a current through them, which is what turns the fan. Once the fan is spinning, this arrangement will also produce a voltage across the coil, which resists further current flow. However, for a moment when you first connect that coil, the magnetic field hasn't had a chance to build up yet, which means the coil of wire looks like a short circuit. That's not a problem for the fan itself, but for other devices on the same circuit, for a moment it will look like there's a short circuit right next to them. As a result, they will see greatly reduced voltage for a moment every time the fan starts.

The easiest solution is generally to move one device or the other to a separate circuit, so that they won't affect each other as much. Since you only have one circuit, you can't completely do that, but you still may have some luck with moving one device or the other to a different outlet across the room, or in a different room. They definitely shouldn't be on the same power strip in any case.

If that doesn't work, our next option is to make the devices play nicely together. As you've noticed, some devices are more tolerant of this short-term brown-out condition than others -- your computer continues to function fine, but your modem/router loses power and reboots. Most modern computer power supplies are designed to work anywhere in the world, and as such have a 'universal' input, capable of using anywhere from ~90V-250V. So when your fan starts up, if the voltage drops from a nominal 120V (or whatever it is in your country), there's still a lot of margin for the power supply to continue functioning. Your router's power supply is probably not like this, and expects a particular input voltage.

However, it's very likely your router's power supply can be replaced with a universal one which will function better under a brownout. (This is assuming your router/modem has an external AC/DC power supply, which most do. If yours takes in AC directly, this won't work.) Check the label of your router's (and modem's, if they're separate devices) power adapter. Your new adapter will need the exact same output voltage rating, and a current output rating equal or greater than the one you have now, with a wide range input voltage rating. Something like this might do the trick: 30W Universal Switching AC/DC power supply.

  • Would you reckon that for the worst-case scenario I add a surge protector for my modem/router line helps? Because it seems to be rather hard to change certain thing within the house considering this is a rather old apartment.
    – Eric L
    Jun 17, 2019 at 20:15
  • 2
    A surge protector won't do anything in this scenario. A surge protector protects against excessive voltage, but your problem is not enough voltage -- a brownout. If you want a plug-in device to protect against this, you need a UPS.
    – Nate S.
    Jun 17, 2019 at 20:18
  • Along the lines of what Nate has asked, can you definitively confirm that if you turn off the breaker for this old house it turns everything off? Can you send us a photo of the breaker panel? Nate @ Russel have both explained the issue. But before buying UPS's new fans, protectors, etc, you really need an idea of how much current you are pulling and is it safe. Would like to help you, but need to decide where to start to do it safely.
    – noybman
    Jun 17, 2019 at 20:36
  • I have a similar problem, though in my case, my external drives, connected via a powered USB hub, are sometimes 'ejected' by my computer when I turn my desk fan on/off and I'm worried about loosing data or corrupting the disks. The hub is powered by a transformer that is co-located with the plug's pins. Would a balun or toroid help in this situation?
    – gone
    Oct 26, 2021 at 6:51

Hey I was facing the Similar issue when I connected a longer LAN wire (about 10m) b/w the modem and router, whenever I would switch on the Fan the router would remain on but the green light of internet would become Red on the Router

But when I replaced that LAN cable b/w Router and Modem with the original LAN cable I got with the router my issue was resolved and there was no effect when I turned on the FAN and the internet would run smoothly.

I hope this Helps


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