Sciencemadness Discussion Board

Lights flickering when hotplaet goes through heating cycle - anything I can do to stop this?

Sidmadra - 16-11-2018 at 13:42

I recently installed from LED lights in my shop and they flicker every few seconds when my hotplate is going through its on/off heating cycle. Is there any economical solution to this? I already have power strip surge protectors being used, but they don't do anything to stop this.

Mr. Rogers - 16-11-2018 at 14:03

Does this happen with a regular incandescent lamp?

You're probably at the limit of that circuit. High current devices can do this when they kick on. If this is what's happening, you need to rearrange what's on that circuit or run a new one if you want to use that hotplate.

EDIT: It's probably not harmful if you have modern wiring.


[Edited on 16-11-2018 by Mr. Rogers]

Texium - 16-11-2018 at 15:19

I have noticed that incandescent lights in the same circuit as my hotplate will dim when the hotplate cycles on. Most LEDs are not intended to be dimmed, and putting an LED bulb on a dimmer typically causes it to flicker. This is probably the same phenomenon that you are witnessing.

Sidmadra - 16-11-2018 at 16:04

Quote: Originally posted by Mr. Rogers  
Does this happen with a regular incandescent lamp?

You're probably at the limit of that circuit. High current devices can do this when they kick on. If this is what's happening, you need to rearrange what's on that circuit or run a new one if you want to use that hotplate.


It's not close to the limit of the circuit. The flickering also happens when any other device kicks on, like my 40w mini fridge, but it only happens for the split second the device kicks on. With the hotplate having an on-off cycle, the flickering is every few seconds.

weilawei - 16-11-2018 at 17:13

The flickering is due to a voltage drop from an excessively long wiring run being made to suddenly draw a current spike. This is common in older construction, where saving on the wiring was all-important. It's especially noticeable with large inductive loads, such as a hotplate or compressor for a fridge, because these cause large current spikes when they turn on and off.

Yes, you can fix it. Run thicker gauge wiring for shorter runs. Basically, spend money. Or, relocate your stuff to closer to the original service.

[Edited on 17-11-2018 by weilawei]

sodium_stearate - 16-11-2018 at 18:31

why not just use real (incandescent) light bulbs?

that way, maybe they will dim a bit when the hotplate
is heating, but they won't flicker such as the annoying
LEDs do.

highpower48 - 17-11-2018 at 10:26

Had same issue with a laser printer and hot air rework station. Solution was to run a shorter 20amp circuit that I use only for these high current draw devices.

Funkerman23 - 17-11-2018 at 10:29

Nice to know I am not the only one who has dealt with this irritating issue. I myself thought long and hard about using a variac and mantles almost exclusively as they are constant current drawing devices, not like the pulsed power supply on most hotplates. This means that you would not have the rhytmic light dimming .
But this isn't a solution where you need a beaker, and while Changbio on ebay does sell reasonably priced overhead stirrers: they are very picky about stirring shaft sizes.You would eithe rneed to use the rubber tubing trick for thinner or fatter diameter stir shafts or replace the chuck with a universal chuck. When I last bought an overhead stirrer it was about 120 USD. the chuck you would need to buy to fix this issue was 80 USD last I was in the market.

WGTR - 17-11-2018 at 13:33

Well, thinking outside the box...power your lights from a battery-powered inverter (maybe a UPS?) and then charge the battery directly with a battery charger plugged into the wall. That would isolate things. I hooked up a 125F 50V supercapacitor module to my 24V UPS, and that runs my computers, etc. Operating the module at half voltage like that will allow it to last for decades. Otherwise (and more practically), just put your hotplate on a completely different circuit. Run an extension cord to another room or something.

Room lights really shouldn't be on the same circuit as the room outlets. If you flip the breaker for the room, do both the outlets and lights turn off? In the United States, the NEC is moving away from allowing this (because you're in a room, overload an outlet, and now you're suddenly standing in the dark).

Mr. Rogers - 17-11-2018 at 18:42

Quote: Originally posted by WGTR  

Room lights really shouldn't be on the same circuit as the room outlets. If you flip the breaker for the room, do both the outlets and lights turn off? In the United States, the NEC is moving away from allowing this (because you're in a room, overload an outlet, and now you're suddenly standing in the dark).


I'm in a house built in 1995 and this is how the rooms are wired. A single 15 amp circuit for outlets and ceiling lights for a regular bedroom without a major appliance.

I have a large HD CRT television from right about the end of the CRT era. When the set is initially turned on, there is a degaussing routine that is powerful enough to sometimes trip the breaker. The set draws more current at startup than even a laser printer or microwave. The set is in the room farthest from the breaker box (essentially the opposite end of the house).


[Edited on 18-11-2018 by Mr. Rogers]

BromicAcid - 17-11-2018 at 20:40

Get a different hot plate. I had this issue recently with a new space heater, warming up was not a problem, but once it was at temperature it would rapidly cycle the power to maintain. This caused intense flickering whereas during the heating cycle the system was able to maintain just fine. Older hot plates tend to have much longer cycles so you don't notice the flickering so much. As mentioned though, incandecent bulbs can help mitigate the issue to some extent but it will be damaging other things on the circuit without a line conditioner.