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First, I debated whether to put this on stack exchange or here, but it seems like it is a tech question that suits this site fine.
Background
I have a room with a 115 V, 6000 BTU window AC unit plugged into one outlet. Then a bunch of electronics (~800 W measured) plugged into a 1500 VA, 900 W UPS plugged in to a second outlet across the room. Finally, I have two 50 W strands of Christmas lights in series (100 W total) I tried to plug into various outlets around the room.
Problem
The first problem is that whenever the room gets too hot, the compressor for the AC unit turns on and the Christmas lights will all flicker. This is not just an annoyance, because the first strand of lights I had in the room actually got burned out one by one, starting at the light closest to the wall outlet.
So I got another strand and was surprised to see the flickering happens even if they are plugged into the UPS (which does have an internal automatic voltage regulator). This made me concerned for the electronics plugged into the UPS, which includes a PC and monitors. However, I do not notice any flicker on the monitor when the compressor turns on. On the other hand, I have been getting some strange pc crashes lately (which would make some sense because only recently did it cool enough for the AC to not be running constantly) that may be related. This could also be due to installing a second gpu recently, etc though.
Questions
I have two main questions:
1) What is the best way to stop the flickering?
2) If the lights are flickering even when plugged into the UPS, should I also be concerned about the other electronics that are obviously also experiencing a momentary power reduction?
Some secondary questions:
3) Does it make sense to put another AVR between the UPS and the wall, eg something like this?
4) Is there something I can put between the AC unit and the wall to help?
5) This is a rental so I would prefer not to do any maintenance on the AC unit, but is this an issue you would report to the landlord?
Any ideas?
(Score: 2) by fraxinus-tree on Monday November 11 2019, @12:02AM (1 child)
Well, I live in Europe, where we have 230v mains and those problems are 1/4 of the US ones by design.
Then again, I have Christmas lights spanning the whole garden and they hardly reach 30-35W total. They are all LED, of course. Most of them have 30v switching-mode power brick and will happily run on anything 90..250v so they refuse to flicker even if you try hard. The oldest strand is directly powered by AC and is actually not outdoor-safe but I use it anyway. It DID flicker once, when landlord's friend came to repair the fence with an ancient transformer-type welding machine. But the lights didn't burn.
So the best course of action is to get LED lights. They won't burn even if they are forced to flicker.
As for the AC unit - the startup current may be higher than usual because of dying condenser. Your incoming power line may have more resistance than it should. Both of these cases are fixable by calling the corresponding technician. Your landlord may or may not help
As for the other electronics: modern PCs, monitors and the likes are generally insensitive to short (and most of them even to extended) brownouts. UPS units are designed with this in mind. There are UPS units that do full conversion and completely filter out these transient events, but they are eeeexpensive. And no, an additional AVR won't help. It may even make the things worse - those things are slow and stupid and are good against slowly changing input voltage. A quick event like those your AC makes may make AVR unit to try to compensate just in time when the input voltage normalizes. So you may get a voltage spike after the dip.
(Score: 0) by Anonymous Coward on Monday November 11 2019, @12:25AM
So do you think the AC just above this was fear mongering?