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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 maxwell demon on Monday November 11 2019, @09:25AM (3 children)
The article also mentioned electronic equipment drawing 800W and Christmas lights of 100W total. That is, the room is constantly heated with almost 900W (note that even LED lamps put more energy into heat than into light; moreover, a large part of that light gets absorbed inside the room, thus also contributing to the room's heating). Not to forget that every human in the room also adds 100W of heating.
Moreover, the article explicitly mentions 115V, which strongly hints at USA and in particular rules out Australia, since
The Tao of math: The numbers you can count are not the real numbers.
(Score: 2) by bzipitidoo on Monday November 11 2019, @01:55PM (2 children)
Ah, yes, I overlooked the explicit mention of 115. Officially, mains in the US are 120V, not 115V. But I often hear 110V thrown around. The US does have places where it does not get cold during the Christmas season, such as the coast of southern California, Florida, the Gulf Coast, and Hawaii, otherwise I'd be wondering, why not just open a window?
I wonder if the submitter has tried to reduce power usage? There is an 80 Plus program to design more efficient computer power supplies. Before 80 Plus began (around 2005), a typical computer power supply was atrociously inefficient. Might not even be 60%, and 70% efficient was exceptional enough that the manufacturer might even brag about it. Now, pretty much everything is at least 80% efficient thanks to the 80 Plus program. If the submitter has the base 80% efficient, might be worthwhile to spring for 80 Plus Gold, Platinum, or Titanium certified power supplies, which are 90%, 92%, and 94% efficient, respectively. If all 800W are used by 80% efficient power supplies, upgrading to 94% efficient will cut that power usage to 680W. Won't have to change a thing on the computing hardware, no compromising or sacrificing at all. However, bigger savings can be achieved by moving from power hungry computers to low power equipment.
But the biggest problem may be that window A/C unit that was mentioned. The inrush is what's killing things. Electric motors draw much more power when starting than when at full speed. That particular unit has an efficiency of only 10.7 EER, and it may not have good mitigation (or any at all) for the inrush. To achieve Energy Star certification, it should be at least 11, as I recall. There are units with EERs over 12. Also, an A/C that is going bad can draw a great deal more power than it should, and it absolutely will trip the breakers. The submitter might want to try an Energy Star rated unit, which should be much better about keeping the inrush down.
(Score: 0) by Anonymous Coward on Monday November 11 2019, @03:18PM (1 child)
This room is on the gulf coast. This is the power supply: https://www.amazon.com/EVGA-Supernova-Platinum-Crossfire-220-P2-1200-X1/dp/B00KYK1CKI [amazon.com]
Also, it is a rental so I really do not want to replace the window AC unit.
(Score: 2) by bzipitidoo on Tuesday November 12 2019, @03:21AM
I salute you for already having an 80 Plus Platinum power supply.
If it works, the simplest thing to do is put the A/C unit on a separate circuit. You may have to do a little checking to find out which outlets are on which circuit breakers, but that's not hard, and doesn't take too terribly long, maybe 15 minutes. Turn a breaker off, and plug a light into each outlet in turn to test if it's live or dead. Moving things to different outlets so the A/C has a circuit to itself may provide enough isolation.
But if the A/C makes lights throughout the entire building dim when it turns on, then you'll have to do something else. One problem is that many of the possible solutions may be more costly than a better window A/C unit.
You could do things manually. Cut power to the lights and electronic equipment, by unplugging them or flipping a switch, let them run off a UPS for a moment, turn the A/C on, wait 3 seconds for it to settle into operation, then restore power to everything else. Far from ideal for gadget lovers who'd much rather have that be automated, but it can be a quick, cheap stopgap until there's something better in place.