10 ms·

Is it okay to daisy chain a UPS?

128 points by nuker 2y ago

delichon 2y ago
I've never found a straight answer on whether it's ok to daisy chain surge protectors. Anyone know? I've been trying to avoid it based on a warning I don't understand, but it can be tough to find power bars without surge protection.
- 4gotunameagain 2y ago
  yes, as they are passive device unless in the case of a surge, which would be shorted to ground by the first one in the row (technically, the first one whose limits are lower than the surge)
  - kosma 2y ago
    The nature of surges is not simple like that - a lightning strike can easily blow MOVs and inrush limiting resistors in multiple devices. I come from a rural area and coming to someone's house with a bag of fresh MOVs and resistors is not an uncommon thing after a big storm.
    - 4gotunameagain 2y ago
      I believe that it highly depends on the type of the surge protector, their ratings and the cable network involved. I do not think that it would cause issues in two surge protectors from power outlets connected in series, and depending on their rating and switching characteristics maybe both could trigger, I agree.
    - numpad0 2y ago
      I believe the question is if it's safe at all to do so rather than whether the protection works or not, though I'd have to be all ears about interactions between multiple parallel surge arrestors.
- kosma 2y ago
  It's not very different from daisy chaining normal extension cords - safe if you know what you're doing (not exceeding the current rating on any of them). Most surge protectors are fused, making them safer to daisy-chain than normal extension cords.
  - sgarland 2y ago
    As an aside, increasing the length of extension cords can cause premature failure of some devices (mostly motorized tools, especially cheaply-made ones) if the wire gauge is inadequate, due to voltage drop. As a general rule, I wouldn’t run tools past 50 feet on anything smaller than 12 AWG (and really, 14 AWG is the smallest I’d go for any length; anything smaller isn’t safe for most loads).
  - quickthrowman 2y ago
    > It's not very different from daisy chaining normal extension cords - safe if you know what you're doing It’s not safe, and it’s expressly forbidden by the NEC, see 11.1.5 below: > 11.1.5 Extension Cords > 11.1.5.1 > Extension cords shall be plugged directly into an approved receptacle, power tap, or multiplug adapter and shall, except for approved multiplug extension cords, serve only one portable appliance. Daisy chaining extension cords is unsafe and not recommended. Only use extension cords that you’ve inspected and are properly rated for the environment (don’t use indoor cords outside, don’t use an outdoor extension cord outdoors unless it’s GFCI protected) and power usage of the device you are powering. Any time electricity has to flow through a splice or mechanical connection, the possibility of a loose connection causing an arc and subsequent fire exists. It’s unlikely to happen to you specifically, but it does happen and avoiding electrical fires is a good thing if it can be avoided. Daisy chaining power strips is also forbidden by the NEC: > 11.1.4.2 > The relocatable power taps shall be directly connected to a permanently installed receptacle.
    - dvdkon 2y ago
      Yes, there is a risk of failure involved with anything electrical, but I don't see why anyone would consider chaining extension cords inherently dangerous enough to ban. It increases the number of connections, but that's a miniscule risk compared to the 5+ connections an extension cord might have on its own. The only significant risk I know is people disregarding the max amperage rating of everything in that chain. For anecdotal experience, I've had both extension cords and wall plugs fail (nothing serious thankfully, but they did get a bit melted), but in those cases it had nothing to do with my extension cord chains, but rather an internal connection failure.
- AstroJetson 2y ago
  You need to know what the cable size is of the power strip and the current you are going to draw. If you have bar A with 14 ga cable plugged into the wall, and bar C With 18 gauge plugged into that, then with devices that don’t exceed C current rating (12 amps) and devices in A ( including the devices in C ) that don’t exceed A’s rating, you will be fine. The other way wall - C - A is the problem, C isn’t able to manage the full load. Only buy known surge suppressor, there have been tear downs where the surge components were missing / fake. Since surge comments are passive, chaining the surge components is not a problem.
  - xprn 2y ago
    Today I learned. I always thought it was some “electricity magic thing” like additional heat generated within the power strips causing issues between the connected devices, but this makes a lot more sense than whatever I was thinking of. Although I do think I might have mixed some things up between regular power strips and those outdoors/industrial ones with a long (double/triple digit meter) rollable cable which my dad was a big user of back when he used to work in construction. Basically back when I was little he used to tell me never to plug power tools into a rolled-up “power wheel”, and I think that when I was later heard you shouldn’t daisy chain power strips I must have made that (wrong) connection.
    - vbezhenar 2y ago
      It's about heat. Cable has some resistance and emits heat. This heat has to dissipate somewhere. If cable is rolled out, it'll dissipate heat to the air. If "power wheel" is not rolled out, cable will heat cables around. Outer cables will dissipate heat to the air, but inner cables will not. So with enough current and enough time, this thing will melt. You probably won't have issues charging iPhone from this thing or powering something for few seconds, so no need to go crazy about it, just something to keep in mind.
    - willis936 2y ago
      Surge protectors do have one magical electrical thingy in them: metal oxide varistors (MOVs). They're what shunt current in an overvoltage transient and they do age with usage.
- willis936 2y ago
  You are not supposed to. The upstream device is sized for a maximum current and daisy chaining can lead to a scenario where downstream devices are sized for larger current than upstream devices, which is avoided everywhere else in electrical distribution. So it's fine as long as you control the strip and keep track of loads (e.g. you know your spouse will never plug a vacuum into that handy receptacle you have there), but at work your EHS team will mark you down for it.
  - vasco 2y ago
    In your example there's a first undersized UPS A, then another UPS B, then whatever combination of electrical devices which power usage exceeds UPS A. You say this is problem. If you have said combination of electrical devices, and if you're assuming we're using an undersized UPS A + the combo of devices, why does the UPS B matter? If you're going to overload the UPS A you're going to overload the UPS A regardless of UPS B, no? Daisy chaining or not, that doesn't seem like the actual problem to a knee-jerk thinking.
  - 4gotunameagain 2y ago
    This is not specific to surge protection, but extension cords in general.
  - xtqv 2y ago
    Daisy chaining is irrelevant to the problem that you can buy 18ga "lighting-only" extensions that bear a 15A rated NEMA 15R but are limited to 8A. Daisy chaining a power bar with it's own circuit breaker can be ideal if it prevents someone from making the mistake of using a circuit in a way that trips a panel breaker, ie preventing your spouse from plugging a vacuum into a circuit shared by several rooms.
  - ta1243 2y ago
    In the UK, if I have a 6 way strip sized for 10A, which thus has a 10A plug in, I could then plug in a 4 way strip downstream with a 5A fuse, then a lamp with a 3A fuse, and that's fine. I could even connect it the other way. If I plug in a heater pulling 10A then sure, the 5A fuse will blow. Daisy chaining multiways will increase the resistance in the earth wire which could mean you end up with a class 1 device with a fault connecting live to earth which would only punting say 8A to earth due to a high resistance (but then your circuit's RCD would trip with that), but is it a major problem? With the US system, do you not have wires capable of 3A (say 24 AWG) which you can connect to a normal socket which also takes a 10A vacuum? If that lamp has a fault where it pulls 6A, what protects the 3A wire -- i.e. there's a fault with your lamp which is plugged into a 15A circuit breaker, and the lamp draws 10A, it wouldn't trip the breaker, and that nice thin 3A lamp cord would melt.
- vbezhenar 2y ago
  As long as you keep load below threshold, I don't see any potential issues.
- deleted 2y ago
  [deleted]
- quickthrowman 2y ago
  It’s not OK, it’s a violation of the NEC: > 11.1.4.2 > The relocatable power taps shall be directly connected to a permanently installed receptacle. A surge protector is a ‘relocatable power tap’ and must be plugged into a permanent receptacle.
- immibis 2y ago
  "surge protector" is what Americans call a passive device that splits one outlet into several, yeah? The danger is overloading. Back in the days when the main things you plugged in were incandescent lights and space heaters, this was probably a big issue. With computer equipment and LED lights you have to have a lot more stuff - many outlets' worth - to reach the circuit's maximum capacity. If the circuit and "surge protectors" are rated for 1800W (15 amps x 120V), officially you should limit yourself to 80% of that for continuous loads which is 1440W, so you can supply 14 laptops or small small desktops that use 100W each, or over 200 raspberry pis on USB chargers that use 5W each, and either way you're going to need a lot of outlets before you come anywhere close to that limit. At least that's a rough estimate. Power factor could decrease that number by up to 50% and you can use the full rating for intermittent loads; I'm not certified to know the fine print. Point is that 10 computers can easily use less power than a single space heater.
  - jcalvinowens 2y ago
    > or over 200 raspberry pis on USB chargers that use 5W each Those little switcher bricks are horribly inefficient: the 15W one I just pulled out of a drawer draws 0.8A on the primary. Realistically you're going to max out a 15A circuit around 20-30 of those, not 96 (1440/15).
  - wnoise 2y ago
    > "surge protector" is what Americans call a passive device that splits one outlet into several, yeah? Technically different, but often combined functions. The splitting bit is a "power strip", or sometimes a "power bar". The surge protection is switching off when there's a short or overvoltage in the supply, or other larger than expected power draw.
  - callalex 2y ago
    >surge protector" is what Americans call a passive device that splits one outlet into several, yeah? Not necessarily. There are “power strips” which turn one receptacle into several. Then there are sure protectors which are typically built into power strips. So not all power strips are surge protectors but almost all surge protectors are also power strips.
- GuB-42 2y ago
  I don't see the problem, provided that you are within the current draw limits. Surge protectors are usually made of components that cause a short when a surge happens, protecting the equipment downstream. It usually pairs with some kind of overcurrent protection (breaker, fuse, sometimes GFCI) to protect against the short the surge protector itself caused. Having chained surge protectors it actually quite common. You may have a surge protector in your breaker panel, then in your powerstrip, then in the power supply of the device you have plugged in. Most good quality ATX power supplies have built-in surge protection for instance. They also all tend to have overcurrent protection too. The breaker panel has breakers (duh), the power strip may have a simple breaker too, and the device may have a fuse. In the UK, the plug itself may have a fuse, plus the breaker from the utility company. The risk from chaining surge protectors is that it increases the risk of false triggers if one of them is defective. But it may also provide better protection. All in all, I wouldn't worry too much about it. Just don't overload that power bar and whatever it is plugged in.
  - WarOnPrivacy 2y ago
    > it may also provide better protection. This has been my experience. There was a corridor between 2 FL counties known for heavy lightning strikes. I serviced small sites that had their IT equip fried (exploded, melted) once or twice a year. Putting it behind 4-6 decent, consumer-grade surge protectors turned out to be really effective. I was a bit surprised given how lightning can jump over protection during a strike. To illustrate the area: An XO's home was hit. Char marks lined the walls wherever wiring ran. Pipes burst all over. Nothing plugged in or wired survived. The front door was blow into the street. His grade school kids were home at the time; they were physically fine.
    - LorenPechtel 2y ago
      There's also the fact that consumer surge protectors are incapable of determining if they're any good or not. There's a small component in there that eats the surge--a severe surge and it's destroyed, it's obvious. However, there's a range in which it no longer functions but is not destroyed. The next surge goes on down the wire. I really wish someone would come up with some surge suppressors that have a string of field-replaceable suppressors. Periodic maintenance, replace the suppressors.
- orblivion 2y ago
  This is funny, I actually am wondering about plugging a surge protector into a UPS. I have some equipment (probably not very high power draw but I can confirm) conveniently zip tied to a peg board along with a power strip that I assume has a basic surge protector on it. One power cord leaves the whole thing, which is very clean, but power goes out a surprising amount here. Can I plug this whole thing into a UPS or should I find a replacement strip without a surge protector?
  - Eisenstein 2y ago
    You can plug it in. The problems with the UPS being plugged into another UPS are related to the internal batteries and the inverters, not to the surge protection. Just don't plug in too many things and overload the UPS.
  - radicality 2y ago
    From what I remember reading, you should not do that. Only plug in PDUs or directly connect equipment to a UPS. You’re meant to put the surge protection before the UPS. I think it’s because the circuitry in surge protectors can mess with what the UPS thinks the actual load is. I believe some UPS brands might also void parts of your warranty if you use them with a surge protector plugged in. https://www.apc.com/us/en/faqs/FA158852/ https://www.apc.com/us/en/faqs/FA158852/
- rinron 2y ago
  probably because it Depends, If you dont know its safer not to. long answer (keep in mind i live in canada, im not a professional, this is just what i learned and trust, keep in mind above) - As long as no wire/bar exceeds its max Amp your safe no matter how many things are plugged in or how long of a daisy chain, the max amp is usually listed. - all devices should list the max amp they use, add up the amp's of all the devices connected to that wire and if its below your safe. - if your breaker is 15 amp, virtually all normal extensions/power bars are rated for at least 15 amps which means doesnt matter what you do the breaker should* flip before any damage is done - if breaker is above 15 amp most surge protectors have protection that will trigger if they exceed their max, most basic "splitters" and extension cords dont, eg if they dont have a switch or reset button they are pretty much guaranteed to not have this protection, be extra carful how much you load on those. some good rules of thumb to keep in mind, look for imprints or labels that list amps, smaller wires can handle less, damaged wires can handle less then they did before and shouldn't be used, if a wire or connector warms when its in use its overloaded reduce the load on it, especially if it warms quickly. here is a video that i liked that talks about it as well https://www.youtube.com/watch?v=K_q-xnYRugQ https://www.youtube.com/watch?v=K_q-xnYRugQ
- dreamcompiler 2y ago
  The reason it's a "bad idea" is that most surge protectors are power strips and you must be cautious when you daisy chain power strips. Likewise extension cords. Why? Two reasons: You have to ensure the wire gauge on every link can handle the current, and at every junction (plug) the resistance is higher than in the wire itself. When electrical fires start they usually start at these plug junctions because they overheat. The surge protectors themselves don't mind being daisy chained.
madaxe_again 2y ago
I mean, it is ok, as long as everything is appropriately sized - I live entirely off grid, with several battery banks and inverters, which are essentially giant UPSs - and have regular UPSs for various equipment so that when I shut the power down for whatever reason the network and servers stay up.
- lambdaone 2y ago
  There are a vast number of problems that all can be summarized as "this is a really stupid thing to do, unless you really know what you are doing". This is one of them.
- dgacmu 2y ago
  Not really. In your case, you probably have a very high quality pure sine wave inverter that's much larger than the individual UPSes, which will make the downstream UPSes mostly happy as long as you don't approach max load. Many cheap inverters are not pure sine, and a UPS seeing this waveform may decide it needs to go to battery also. Practically, a UPS also adds to the current draw, and many people may accidentally exceed the circuit limit because they only look at the useful load but not also the UPS charging load after a power failure ends.
- K0balt 2y ago
  Same here, I run a lot of different equipment on grden variety UPS's on our solar grid - but that is fed by redundant 18KW three-phase inverters and 72KWH of batteries... so that probably looks a lot like utility power from the perspective of the UPS's. Overall, the discussion tangentially reminds me of a common theme in aviation - twin vs single engine aircraft. With two engines, the chance of having an engine failure at a critical time is doubled.
  - immibis 2y ago
    But you also have a good chance to get through the failure with one working engine. A two engine plane with one working engine climbs slowly, and a one engine plane with zero working engines doesn't climb at all.
chx 2y ago
Note the last image of the article is not correct, if you want full redundancy you need two independent power feeds. How independent depends on your needs of course. You might just want to run it from a different circuit but the same utility power. If you've got insane needs and megabucks you can talk to the utility about being fed from two substations or at the extreme end you can get one feed from the utility and you can make your own second feed. Traditionally we did this with water turbine working from a river but today I might look into solar and perhaps molten salt. As an example, way back then when this was a very lucrative business, we placed the servers for a premium number erotic call in an industrial park on the border of two districts in Budapest because that's where we could get two independent power feeds without running our own lines. Internet connection wise, one was a simple leased line the other was a microwave connection to very far away. Short of bombing the entire site it was fair impossible for the installation to go offline and -- for the six years I knew about it, it never did. Note the site served German callers, that's where the big bucks came from.
- okr 2y ago
  [flagged]
  - Germanion 2y ago
    Huh? How did we subsidized east European erotic call centers?
    - lima 2y ago
      By calling them
      - Germanion 2y ago
        That's just wrong use of words. And weird accusations like we Germans did this on purpose like mafia
        rendall 2y ago
nuker 2y ago
The main point against seems to be that downstream UPS will not like "simulated or modified sine wave" if upstream UPS is not producing "Pure sine wave". To be tested :)
- dgacmu 2y ago
  I've tested it before. TFA is correct, at least with the APC UPS I tried it with once. The apc ups went to battery and then turned off when out of battery.
  - nuker 2y ago
    Thanks! But why they don't like it? UPS, as a black box, should harvest whatever energy is in the source, regardless is it sine wave or freaking square mess. Even DC or RF is present :) Why so picky?
    - boricj 2y ago
      That's true to an extent for online UPSes, which converts from AC to DC and then from DC to AC, completely isolating the input current from the output, but these are the most expensive types of UPSes. Your run-of-the-mill UPS is likely to either be offline, which forwards the input to the output, or line-interactive, which can compensate to an extent under or over voltage conditions with a regulator. If the input current characteristics are outside allowable tolerances, they can't compensate and must switch the load to battery to continue powering it.
      - nuker 2y ago
        > If the input current characteristics are outside allowable tolerances This is the key to this whole discussion. I guess it boils down to existing line-interactive designs, why they can't work with simulated sine as a source.
        dgacmu 2y ago
        A transfer-switch based UPS still needs to protect against brownouts, so it too has line behavior parameters outside of which it will switch to battery. It's an interesting question if/why a modified sine wave input would trigger that or not. Probably one of those "it depends on the design" things. (modified sine -> approximately an oscillating square wave.) A dual-conversion (online) UPS is almost certainly more robust as far as what kinds of inputs it can accept (though as GP noted, they're more expensive, and they're also less efficient due to the additional rectification->inverter).
myself248 2y ago
Another thing they don't mention is that when utility AC returns, each UPS in the chain tries to recharge, which can be a significant chunk of power. Any given UPS is sized so that its downstream load plus its own recharging power doesn't overdraw the circuit, but add two recharging powers and it's much more likely. I don't think this is an issue with double-conversion UPSs, since their input power is fixed by their rectifier size and they'll simply charge more slowly instead, but with standby type, it's very much a concern.
lucumo 2y ago
What a stupid article. It doesn't tell you anything beyond "no, buy our products instead". WHY is it bad? HOW does it fail? I mean, it's possible that I don't know enough about UPSes to understand the finer details and all this would be obvious to someone who does. But presumably they already know why it's a bad idea, and don't need this particular article to explain them. The amount of scare words and the lack of detail honestly make me believe it probably IS okay to do, and Eaton just wants to scam some extra money out of people. It's just the posts in this thread that make me take it slightly more seriously.
- tssge 2y ago
  >Eaton just wants to scam some extra money out of people Seems quite improbable that would be the purpose of the article. The article is basically saying "buy a single UPS instead of buying two to daisy chain them expecting to get better results". If anything, such advice would lead to people buying less devices. Of course if one had two UPSes laying around for nothing, then I guess daisy chaining might come to mind to get better capacity or something for no extra price. However, generally people don't randomly have UPSs laying around for no reason, so it would make sense to buy higher capacity UPS than two lower capacity UPSs to daisy chain them anyways (and for probably quite similar total cost of ownership).
  - nixpulvis 2y ago
    Let’s say I do have two UPSs lying around though, and a soldering iron.
- pixl97 2y ago
  >make me believe it probably IS okay to do Yea, as someone that ran their own micro ISP for a while, and worked for larger ISPs, no it's not ok to do at all. APC brand was the absolute worst about immediately tripping when plugged into another UPS. Eaton online UPS' actually handled it ok in comparison, but they are typically pretty expensive units. This is definitely a case of the vendor attempting to save you money. Get an ATS on anything that doesn't accept dual power.
Waterluvian 2y ago
I’m guessing the sine waves wouldn’t line up? Edit: derp. Wouldn’t matter. I was thinking putting them in parallel.
CapitalistCartr 2y ago
The places I've worked on used multiple generators, more than was required to keep running. Home Shopping Network had 8, 5 of which would keep them on air. That's an extremely reliable backup.
- toxic72 2y ago
  Can you share more about the Home Shopping Network's broadcast infrastructure - that's such an explored little nugget of the world I've never given any thought to before
  - CapitalistCartr 2y ago
    This is 30+ years ago, they had a halon system. They had calculated the volume of the rooms, including the contents so as to not kill people while supressing fire. So making a hole in a wall, or adding/subtracting anything was a huge production.
NelsonMinar 2y ago
This page is SEO crap. A thin article with little technical content peppered with links to the company's own products.
rietta 2y ago
I know from experience that plugging an old school digital alarm clock into a UPS does not work. The clock drifts badly. Turns out those use the AC cycle rate as their clock.
- kadoban 2y ago
  It should depend on the UPS, some I believe are indistinguishable from wall power, especially without actually trying. Even for the cheaper UPSes I wonder if the issue isn't the cycle rate, but the cycle shape? My understanding is that they tend to be able to hit 60Hz pretty easily, but the cheaper ones are a ~square wave instead of a ~sine wave. Maybe the digital clock just glitches on that more.
  - yafosuda 2y ago
    To clarify this comment: there are two primary types of UPS, double conversion and line interactive. Double conversion takes power from AC, converts it to DC to charge batteries, takes battery output, and inverts it back to AC. All power drawn from the UPS goes through the battery and inverter stack, and there is no transient/power loss when AC mains are lost. They tend to be more expensive, louder, run hotter, etc. Line interactive UPSs, on the other hand, tend to be cheaper and are in most cheap consumer products. They take AC mains, convert it to DC, and charge batteries. But AC mains is also connected directly to the output device through switch circuitry that will quickly switch the power source from AC mains to batteries/inverter if power loss is detected. Reputable UPSs will use pure sine wave inverters for converting DC battery back to AC. Modified sine waves are indeed a lot cheaper but are not suitable for some sensitive equipment.
- LorenPechtel 2y ago
  Yup, made a variation of this mistake once long ago. Ordinary clock, plugged into a transformer connected to Chinese (220/50) power. It ran 20% slow.
digitalsushi 2y ago
I had an underpowered battery backup for my desk, and was using it for my gaming PC, two laptops, and two external monitors, and all my peripherals. (It didnt occur to me I was overrunning it, otherwise my rant here is nonsensical) The monitors both had the same general issue - they would fail to find a signal every few weeks, and I'd find that waiting a few hours with them turned off would help. I have pages of notes here. Another way to get them to work would be booting up the windows computer, which would seem to 'trick' the monitor into getting a signal on hdmi, and then I could switch to display port for the mac laptops to be used. Anyways it's all crazy rambling notes, with copious timestamps, looking for patterns. I have an IR heat thermometer from the kitchen and my monitor vents would regularly have air over 160F coming out the tops when the monitors would not even post the vendor logo after a hard power reset. I removed the battery backup and it's been months now with zero blips. So the only obvious takeaway I have is that overrunning a battery is a completely worthless endeavor.
- lmpdev 2y ago
  What I find insane is the peak current discharge those little 12V 7-9ah backup batteries can push out Well over 100A for a few seconds Lithium can’t even do that in a single cell (but in turn is infinitely better for continuous current) It sort of baffles me intuitively that an extremely simple lead battery can for a short while compete with the grid
  - jpgvm 2y ago
    Yeah this is why lead acid was hard to replace in cars with lithium chemistries. The Cold Cranking Amps (pretty much the peak startup current) that they can provide is rather insane. Even my small motorcycle battery provides over 250 CCA.
    - elintknower 2y ago
      Super capacitors / just large capacitors in general might eventually save the day here. The only issue is super capacitors can't generally bake in the heat all day and still work for 3-5 years like lead acid batteries can. Supercaps is how "fast" charging in most smartphones works as well since they can soak current faster than the battery itself and also mitigate cycling batteries too hard.
deleted 2y ago
[deleted]
danjl 2y ago
Do kids these days actually make Daisy chains anymore? You know, with real Daisy flowers.
- AzzyHN 2y ago
  I was unaware that was the origin of the term, so probably not
- m463 2y ago
  I remember chewing gum wrapper chains made by tricky folding.
elintknower 2y ago
Is anyone else here using Ecoflow batteries as a UPS backup? I really wish Eeaton would produce a similar consumer facing function that is intended to be used long-term 24/7 not just on weekend trips etc.
necovek 2y ago
This is the type of article I find useless. It would be great if Eaton went to the trouble to explain what exact conditions the two UPSes need to fulfill to be successfully daisy chained, which would probably put people away from doing it anyway. But it would also be a much more informative article, and also positively framed, which is always a much better read.
- deadbunny 2y ago
  That just leads to "I followed your instructions on your website and my house burned down". No company is going to open themselves up to that.
  - necovek 2y ago
    I know US is very litigious, but I am certain there are plenty of knowledge-based articles by companies in the US of A that could theoretically be tested in court this way, but really, aren't. I mean, look for any mention of "slow-roast it for 12 hours" in your favourite web search engine (I notice a couple of those say "overnight", yikes).
- zootboy 2y ago
  They don't explain it because it basically never makes sense to daisy-chain a UPS. If you want redundancy in your power supply chain, use a dual-PSU computer. If you want longer backup times, get a UPS with a bigger battery.
  - BuildTheRobots 2y ago
    The only time I think it makes sense if if you're doing a belt+braces with colo'd stuff in a datacentre. The DC will have its own UPS system, but in the event it all goes wrong (which happens more often than I'd like) you probably want something in your cab that can give your equipment notification and time to shut down safely, and provide surge suppression and maybe some level of isolation from the inevitable back-emf caused by the rest of the hall going dark.
  - 2y ago
dusted 2y ago
Interesting. I'm sure it's correct, but it makes me wonder about the output quality of these devices. If the output of an UPS is so significantly different from regular utility power that it's unsuitable as input for an UPS, then it must be of a worse quality and unsuitable for the expensive equipment it's supposed to power ? I do understand the logic that chaining UPS will cause interesting things to happen when power is restored and the downstream UPS can then overload the upstream UPS because it will incur additional load when charging its battery, which could trigger overload protection in the upstream device.

128 points by nuker 2y ago

I've never found a straight answer on whether it's ok to daisy chain surge protectors. Anyone know? I've been trying to avoid it based on a warning I don't understand, but it can be tough to find power bars without surge protection.

4gotunameagain 2y ago
yes, as they are passive device unless in the case of a surge, which would be shorted to ground by the first one in the row (technically, the first one whose limits are lower than the surge)
- kosma 2y ago
  The nature of surges is not simple like that - a lightning strike can easily blow MOVs and inrush limiting resistors in multiple devices. I come from a rural area and coming to someone's house with a bag of fresh MOVs and resistors is not an uncommon thing after a big storm.
  - 4gotunameagain 2y ago
    I believe that it highly depends on the type of the surge protector, their ratings and the cable network involved. I do not think that it would cause issues in two surge protectors from power outlets connected in series, and depending on their rating and switching characteristics maybe both could trigger, I agree.
  - numpad0 2y ago
    I believe the question is if it's safe at all to do so rather than whether the protection works or not, though I'd have to be all ears about interactions between multiple parallel surge arrestors.
kosma 2y ago
It's not very different from daisy chaining normal extension cords - safe if you know what you're doing (not exceeding the current rating on any of them). Most surge protectors are fused, making them safer to daisy-chain than normal extension cords.
- sgarland 2y ago
  As an aside, increasing the length of extension cords can cause premature failure of some devices (mostly motorized tools, especially cheaply-made ones) if the wire gauge is inadequate, due to voltage drop. As a general rule, I wouldn’t run tools past 50 feet on anything smaller than 12 AWG (and really, 14 AWG is the smallest I’d go for any length; anything smaller isn’t safe for most loads).
- quickthrowman 2y ago
  > It's not very different from daisy chaining normal extension cords - safe if you know what you're doing It’s not safe, and it’s expressly forbidden by the NEC, see 11.1.5 below: > 11.1.5 Extension Cords > 11.1.5.1 > Extension cords shall be plugged directly into an approved receptacle, power tap, or multiplug adapter and shall, except for approved multiplug extension cords, serve only one portable appliance. Daisy chaining extension cords is unsafe and not recommended. Only use extension cords that you’ve inspected and are properly rated for the environment (don’t use indoor cords outside, don’t use an outdoor extension cord outdoors unless it’s GFCI protected) and power usage of the device you are powering. Any time electricity has to flow through a splice or mechanical connection, the possibility of a loose connection causing an arc and subsequent fire exists. It’s unlikely to happen to you specifically, but it does happen and avoiding electrical fires is a good thing if it can be avoided. Daisy chaining power strips is also forbidden by the NEC: > 11.1.4.2 > The relocatable power taps shall be directly connected to a permanently installed receptacle.
  - dvdkon 2y ago
    Yes, there is a risk of failure involved with anything electrical, but I don't see why anyone would consider chaining extension cords inherently dangerous enough to ban. It increases the number of connections, but that's a miniscule risk compared to the 5+ connections an extension cord might have on its own. The only significant risk I know is people disregarding the max amperage rating of everything in that chain. For anecdotal experience, I've had both extension cords and wall plugs fail (nothing serious thankfully, but they did get a bit melted), but in those cases it had nothing to do with my extension cord chains, but rather an internal connection failure.
AstroJetson 2y ago
You need to know what the cable size is of the power strip and the current you are going to draw. If you have bar A with 14 ga cable plugged into the wall, and bar C With 18 gauge plugged into that, then with devices that don’t exceed C current rating (12 amps) and devices in A ( including the devices in C ) that don’t exceed A’s rating, you will be fine. The other way wall - C - A is the problem, C isn’t able to manage the full load. Only buy known surge suppressor, there have been tear downs where the surge components were missing / fake. Since surge comments are passive, chaining the surge components is not a problem.
- xprn 2y ago
  Today I learned. I always thought it was some “electricity magic thing” like additional heat generated within the power strips causing issues between the connected devices, but this makes a lot more sense than whatever I was thinking of. Although I do think I might have mixed some things up between regular power strips and those outdoors/industrial ones with a long (double/triple digit meter) rollable cable which my dad was a big user of back when he used to work in construction. Basically back when I was little he used to tell me never to plug power tools into a rolled-up “power wheel”, and I think that when I was later heard you shouldn’t daisy chain power strips I must have made that (wrong) connection.
  - vbezhenar 2y ago
    It's about heat. Cable has some resistance and emits heat. This heat has to dissipate somewhere. If cable is rolled out, it'll dissipate heat to the air. If "power wheel" is not rolled out, cable will heat cables around. Outer cables will dissipate heat to the air, but inner cables will not. So with enough current and enough time, this thing will melt. You probably won't have issues charging iPhone from this thing or powering something for few seconds, so no need to go crazy about it, just something to keep in mind.
  - willis936 2y ago
    Surge protectors do have one magical electrical thingy in them: metal oxide varistors (MOVs). They're what shunt current in an overvoltage transient and they do age with usage.
willis936 2y ago
You are not supposed to. The upstream device is sized for a maximum current and daisy chaining can lead to a scenario where downstream devices are sized for larger current than upstream devices, which is avoided everywhere else in electrical distribution. So it's fine as long as you control the strip and keep track of loads (e.g. you know your spouse will never plug a vacuum into that handy receptacle you have there), but at work your EHS team will mark you down for it.
- vasco 2y ago
  In your example there's a first undersized UPS A, then another UPS B, then whatever combination of electrical devices which power usage exceeds UPS A. You say this is problem. If you have said combination of electrical devices, and if you're assuming we're using an undersized UPS A + the combo of devices, why does the UPS B matter? If you're going to overload the UPS A you're going to overload the UPS A regardless of UPS B, no? Daisy chaining or not, that doesn't seem like the actual problem to a knee-jerk thinking.
- 4gotunameagain 2y ago
  This is not specific to surge protection, but extension cords in general.
- xtqv 2y ago
  Daisy chaining is irrelevant to the problem that you can buy 18ga "lighting-only" extensions that bear a 15A rated NEMA 15R but are limited to 8A. Daisy chaining a power bar with it's own circuit breaker can be ideal if it prevents someone from making the mistake of using a circuit in a way that trips a panel breaker, ie preventing your spouse from plugging a vacuum into a circuit shared by several rooms.
- ta1243 2y ago
  In the UK, if I have a 6 way strip sized for 10A, which thus has a 10A plug in, I could then plug in a 4 way strip downstream with a 5A fuse, then a lamp with a 3A fuse, and that's fine. I could even connect it the other way. If I plug in a heater pulling 10A then sure, the 5A fuse will blow. Daisy chaining multiways will increase the resistance in the earth wire which could mean you end up with a class 1 device with a fault connecting live to earth which would only punting say 8A to earth due to a high resistance (but then your circuit's RCD would trip with that), but is it a major problem? With the US system, do you not have wires capable of 3A (say 24 AWG) which you can connect to a normal socket which also takes a 10A vacuum? If that lamp has a fault where it pulls 6A, what protects the 3A wire -- i.e. there's a fault with your lamp which is plugged into a 15A circuit breaker, and the lamp draws 10A, it wouldn't trip the breaker, and that nice thin 3A lamp cord would melt.
vbezhenar 2y ago
As long as you keep load below threshold, I don't see any potential issues.
deleted 2y ago
[deleted]
quickthrowman 2y ago
It’s not OK, it’s a violation of the NEC: > 11.1.4.2 > The relocatable power taps shall be directly connected to a permanently installed receptacle. A surge protector is a ‘relocatable power tap’ and must be plugged into a permanent receptacle.
immibis 2y ago
"surge protector" is what Americans call a passive device that splits one outlet into several, yeah? The danger is overloading. Back in the days when the main things you plugged in were incandescent lights and space heaters, this was probably a big issue. With computer equipment and LED lights you have to have a lot more stuff - many outlets' worth - to reach the circuit's maximum capacity. If the circuit and "surge protectors" are rated for 1800W (15 amps x 120V), officially you should limit yourself to 80% of that for continuous loads which is 1440W, so you can supply 14 laptops or small small desktops that use 100W each, or over 200 raspberry pis on USB chargers that use 5W each, and either way you're going to need a lot of outlets before you come anywhere close to that limit. At least that's a rough estimate. Power factor could decrease that number by up to 50% and you can use the full rating for intermittent loads; I'm not certified to know the fine print. Point is that 10 computers can easily use less power than a single space heater.
- jcalvinowens 2y ago
  > or over 200 raspberry pis on USB chargers that use 5W each Those little switcher bricks are horribly inefficient: the 15W one I just pulled out of a drawer draws 0.8A on the primary. Realistically you're going to max out a 15A circuit around 20-30 of those, not 96 (1440/15).
- wnoise 2y ago
  > "surge protector" is what Americans call a passive device that splits one outlet into several, yeah? Technically different, but often combined functions. The splitting bit is a "power strip", or sometimes a "power bar". The surge protection is switching off when there's a short or overvoltage in the supply, or other larger than expected power draw.
- callalex 2y ago
  >surge protector" is what Americans call a passive device that splits one outlet into several, yeah? Not necessarily. There are “power strips” which turn one receptacle into several. Then there are sure protectors which are typically built into power strips. So not all power strips are surge protectors but almost all surge protectors are also power strips.
GuB-42 2y ago
I don't see the problem, provided that you are within the current draw limits. Surge protectors are usually made of components that cause a short when a surge happens, protecting the equipment downstream. It usually pairs with some kind of overcurrent protection (breaker, fuse, sometimes GFCI) to protect against the short the surge protector itself caused. Having chained surge protectors it actually quite common. You may have a surge protector in your breaker panel, then in your powerstrip, then in the power supply of the device you have plugged in. Most good quality ATX power supplies have built-in surge protection for instance. They also all tend to have overcurrent protection too. The breaker panel has breakers (duh), the power strip may have a simple breaker too, and the device may have a fuse. In the UK, the plug itself may have a fuse, plus the breaker from the utility company. The risk from chaining surge protectors is that it increases the risk of false triggers if one of them is defective. But it may also provide better protection. All in all, I wouldn't worry too much about it. Just don't overload that power bar and whatever it is plugged in.
- WarOnPrivacy 2y ago
  > it may also provide better protection. This has been my experience. There was a corridor between 2 FL counties known for heavy lightning strikes. I serviced small sites that had their IT equip fried (exploded, melted) once or twice a year. Putting it behind 4-6 decent, consumer-grade surge protectors turned out to be really effective. I was a bit surprised given how lightning can jump over protection during a strike. To illustrate the area: An XO's home was hit. Char marks lined the walls wherever wiring ran. Pipes burst all over. Nothing plugged in or wired survived. The front door was blow into the street. His grade school kids were home at the time; they were physically fine.
  - LorenPechtel 2y ago
    There's also the fact that consumer surge protectors are incapable of determining if they're any good or not. There's a small component in there that eats the surge--a severe surge and it's destroyed, it's obvious. However, there's a range in which it no longer functions but is not destroyed. The next surge goes on down the wire. I really wish someone would come up with some surge suppressors that have a string of field-replaceable suppressors. Periodic maintenance, replace the suppressors.
orblivion 2y ago
This is funny, I actually am wondering about plugging a surge protector into a UPS. I have some equipment (probably not very high power draw but I can confirm) conveniently zip tied to a peg board along with a power strip that I assume has a basic surge protector on it. One power cord leaves the whole thing, which is very clean, but power goes out a surprising amount here. Can I plug this whole thing into a UPS or should I find a replacement strip without a surge protector?
- Eisenstein 2y ago
  You can plug it in. The problems with the UPS being plugged into another UPS are related to the internal batteries and the inverters, not to the surge protection. Just don't plug in too many things and overload the UPS.
- radicality 2y ago
  From what I remember reading, you should not do that. Only plug in PDUs or directly connect equipment to a UPS. You’re meant to put the surge protection before the UPS. I think it’s because the circuitry in surge protectors can mess with what the UPS thinks the actual load is. I believe some UPS brands might also void parts of your warranty if you use them with a surge protector plugged in. https://www.apc.com/us/en/faqs/FA158852/ https://www.apc.com/us/en/faqs/FA158852/
rinron 2y ago
probably because it Depends, If you dont know its safer not to. long answer (keep in mind i live in canada, im not a professional, this is just what i learned and trust, keep in mind above) - As long as no wire/bar exceeds its max Amp your safe no matter how many things are plugged in or how long of a daisy chain, the max amp is usually listed. - all devices should list the max amp they use, add up the amp's of all the devices connected to that wire and if its below your safe. - if your breaker is 15 amp, virtually all normal extensions/power bars are rated for at least 15 amps which means doesnt matter what you do the breaker should* flip before any damage is done - if breaker is above 15 amp most surge protectors have protection that will trigger if they exceed their max, most basic "splitters" and extension cords dont, eg if they dont have a switch or reset button they are pretty much guaranteed to not have this protection, be extra carful how much you load on those. some good rules of thumb to keep in mind, look for imprints or labels that list amps, smaller wires can handle less, damaged wires can handle less then they did before and shouldn't be used, if a wire or connector warms when its in use its overloaded reduce the load on it, especially if it warms quickly. here is a video that i liked that talks about it as well https://www.youtube.com/watch?v=K_q-xnYRugQ https://www.youtube.com/watch?v=K_q-xnYRugQ
dreamcompiler 2y ago
The reason it's a "bad idea" is that most surge protectors are power strips and you must be cautious when you daisy chain power strips. Likewise extension cords. Why? Two reasons: You have to ensure the wire gauge on every link can handle the current, and at every junction (plug) the resistance is higher than in the wire itself. When electrical fires start they usually start at these plug junctions because they overheat. The surge protectors themselves don't mind being daisy chained.

madaxe_again 2y ago

I mean, it is ok, as long as everything is appropriately sized - I live entirely off grid, with several battery banks and inverters, which are essentially giant UPSs - and have regular UPSs for various equipment so that when I shut the power down for whatever reason the network and servers stay up.

lambdaone 2y ago
There are a vast number of problems that all can be summarized as "this is a really stupid thing to do, unless you really know what you are doing". This is one of them.
dgacmu 2y ago
Not really. In your case, you probably have a very high quality pure sine wave inverter that's much larger than the individual UPSes, which will make the downstream UPSes mostly happy as long as you don't approach max load. Many cheap inverters are not pure sine, and a UPS seeing this waveform may decide it needs to go to battery also. Practically, a UPS also adds to the current draw, and many people may accidentally exceed the circuit limit because they only look at the useful load but not also the UPS charging load after a power failure ends.
K0balt 2y ago
Same here, I run a lot of different equipment on grden variety UPS's on our solar grid - but that is fed by redundant 18KW three-phase inverters and 72KWH of batteries... so that probably looks a lot like utility power from the perspective of the UPS's. Overall, the discussion tangentially reminds me of a common theme in aviation - twin vs single engine aircraft. With two engines, the chance of having an engine failure at a critical time is doubled.
- immibis 2y ago
  But you also have a good chance to get through the failure with one working engine. A two engine plane with one working engine climbs slowly, and a one engine plane with zero working engines doesn't climb at all.

chx 2y ago

Note the last image of the article is not correct, if you want full redundancy you need two independent power feeds. How independent depends on your needs of course. You might just want to run it from a different circuit but the same utility power. If you've got insane needs and megabucks you can talk to the utility about being fed from two substations or at the extreme end you can get one feed from the utility and you can make your own second feed. Traditionally we did this with water turbine working from a river but today I might look into solar and perhaps molten salt. As an example, way back then when this was a very lucrative business, we placed the servers for a premium number erotic call in an industrial park on the border of two districts in Budapest because that's where we could get two independent power feeds without running our own lines. Internet connection wise, one was a simple leased line the other was a microwave connection to very far away. Short of bombing the entire site it was fair impossible for the installation to go offline and -- for the six years I knew about it, it never did. Note the site served German callers, that's where the big bucks came from.

okr 2y ago
[flagged]
- Germanion 2y ago
  Huh? How did we subsidized east European erotic call centers?
  - lima 2y ago
    By calling them
    - Germanion 2y ago
      That's just wrong use of words. And weird accusations like we Germans did this on purpose like mafia
      - rendall 2y ago

nuker 2y ago

The main point against seems to be that downstream UPS will not like "simulated or modified sine wave" if upstream UPS is not producing "Pure sine wave". To be tested :)

dgacmu 2y ago
I've tested it before. TFA is correct, at least with the APC UPS I tried it with once. The apc ups went to battery and then turned off when out of battery.
- nuker 2y ago
  Thanks! But why they don't like it? UPS, as a black box, should harvest whatever energy is in the source, regardless is it sine wave or freaking square mess. Even DC or RF is present :) Why so picky?
  - boricj 2y ago
    That's true to an extent for online UPSes, which converts from AC to DC and then from DC to AC, completely isolating the input current from the output, but these are the most expensive types of UPSes. Your run-of-the-mill UPS is likely to either be offline, which forwards the input to the output, or line-interactive, which can compensate to an extent under or over voltage conditions with a regulator. If the input current characteristics are outside allowable tolerances, they can't compensate and must switch the load to battery to continue powering it.
    - nuker 2y ago
      > If the input current characteristics are outside allowable tolerances This is the key to this whole discussion. I guess it boils down to existing line-interactive designs, why they can't work with simulated sine as a source.
      - dgacmu 2y ago
        A transfer-switch based UPS still needs to protect against brownouts, so it too has line behavior parameters outside of which it will switch to battery. It's an interesting question if/why a modified sine wave input would trigger that or not. Probably one of those "it depends on the design" things. (modified sine -> approximately an oscillating square wave.) A dual-conversion (online) UPS is almost certainly more robust as far as what kinds of inputs it can accept (though as GP noted, they're more expensive, and they're also less efficient due to the additional rectification->inverter).

myself248 2y ago

Another thing they don't mention is that when utility AC returns, each UPS in the chain tries to recharge, which can be a significant chunk of power. Any given UPS is sized so that its downstream load plus its own recharging power doesn't overdraw the circuit, but add two recharging powers and it's much more likely. I don't think this is an issue with double-conversion UPSs, since their input power is fixed by their rectifier size and they'll simply charge more slowly instead, but with standby type, it's very much a concern.

lucumo 2y ago

What a stupid article. It doesn't tell you anything beyond "no, buy our products instead". WHY is it bad? HOW does it fail? I mean, it's possible that I don't know enough about UPSes to understand the finer details and all this would be obvious to someone who does. But presumably they already know why it's a bad idea, and don't need this particular article to explain them. The amount of scare words and the lack of detail honestly make me believe it probably IS okay to do, and Eaton just wants to scam some extra money out of people. It's just the posts in this thread that make me take it slightly more seriously.

tssge 2y ago
>Eaton just wants to scam some extra money out of people Seems quite improbable that would be the purpose of the article. The article is basically saying "buy a single UPS instead of buying two to daisy chain them expecting to get better results". If anything, such advice would lead to people buying less devices. Of course if one had two UPSes laying around for nothing, then I guess daisy chaining might come to mind to get better capacity or something for no extra price. However, generally people don't randomly have UPSs laying around for no reason, so it would make sense to buy higher capacity UPS than two lower capacity UPSs to daisy chain them anyways (and for probably quite similar total cost of ownership).
- nixpulvis 2y ago
  Let’s say I do have two UPSs lying around though, and a soldering iron.
pixl97 2y ago
>make me believe it probably IS okay to do Yea, as someone that ran their own micro ISP for a while, and worked for larger ISPs, no it's not ok to do at all. APC brand was the absolute worst about immediately tripping when plugged into another UPS. Eaton online UPS' actually handled it ok in comparison, but they are typically pretty expensive units. This is definitely a case of the vendor attempting to save you money. Get an ATS on anything that doesn't accept dual power.

Waterluvian 2y ago

I’m guessing the sine waves wouldn’t line up? Edit: derp. Wouldn’t matter. I was thinking putting them in parallel.

CapitalistCartr 2y ago

The places I've worked on used multiple generators, more than was required to keep running. Home Shopping Network had 8, 5 of which would keep them on air. That's an extremely reliable backup.

toxic72 2y ago
Can you share more about the Home Shopping Network's broadcast infrastructure - that's such an explored little nugget of the world I've never given any thought to before
- CapitalistCartr 2y ago
  This is 30+ years ago, they had a halon system. They had calculated the volume of the rooms, including the contents so as to not kill people while supressing fire. So making a hole in a wall, or adding/subtracting anything was a huge production.

NelsonMinar 2y ago

This page is SEO crap. A thin article with little technical content peppered with links to the company's own products.

rietta 2y ago

I know from experience that plugging an old school digital alarm clock into a UPS does not work. The clock drifts badly. Turns out those use the AC cycle rate as their clock.

kadoban 2y ago
It should depend on the UPS, some I believe are indistinguishable from wall power, especially without actually trying. Even for the cheaper UPSes I wonder if the issue isn't the cycle rate, but the cycle shape? My understanding is that they tend to be able to hit 60Hz pretty easily, but the cheaper ones are a ~square wave instead of a ~sine wave. Maybe the digital clock just glitches on that more.
- yafosuda 2y ago
  To clarify this comment: there are two primary types of UPS, double conversion and line interactive. Double conversion takes power from AC, converts it to DC to charge batteries, takes battery output, and inverts it back to AC. All power drawn from the UPS goes through the battery and inverter stack, and there is no transient/power loss when AC mains are lost. They tend to be more expensive, louder, run hotter, etc. Line interactive UPSs, on the other hand, tend to be cheaper and are in most cheap consumer products. They take AC mains, convert it to DC, and charge batteries. But AC mains is also connected directly to the output device through switch circuitry that will quickly switch the power source from AC mains to batteries/inverter if power loss is detected. Reputable UPSs will use pure sine wave inverters for converting DC battery back to AC. Modified sine waves are indeed a lot cheaper but are not suitable for some sensitive equipment.
LorenPechtel 2y ago
Yup, made a variation of this mistake once long ago. Ordinary clock, plugged into a transformer connected to Chinese (220/50) power. It ran 20% slow.

digitalsushi 2y ago

I had an underpowered battery backup for my desk, and was using it for my gaming PC, two laptops, and two external monitors, and all my peripherals. (It didnt occur to me I was overrunning it, otherwise my rant here is nonsensical) The monitors both had the same general issue - they would fail to find a signal every few weeks, and I'd find that waiting a few hours with them turned off would help. I have pages of notes here. Another way to get them to work would be booting up the windows computer, which would seem to 'trick' the monitor into getting a signal on hdmi, and then I could switch to display port for the mac laptops to be used. Anyways it's all crazy rambling notes, with copious timestamps, looking for patterns. I have an IR heat thermometer from the kitchen and my monitor vents would regularly have air over 160F coming out the tops when the monitors would not even post the vendor logo after a hard power reset. I removed the battery backup and it's been months now with zero blips. So the only obvious takeaway I have is that overrunning a battery is a completely worthless endeavor.

lmpdev 2y ago
What I find insane is the peak current discharge those little 12V 7-9ah backup batteries can push out Well over 100A for a few seconds Lithium can’t even do that in a single cell (but in turn is infinitely better for continuous current) It sort of baffles me intuitively that an extremely simple lead battery can for a short while compete with the grid
- jpgvm 2y ago
  Yeah this is why lead acid was hard to replace in cars with lithium chemistries. The Cold Cranking Amps (pretty much the peak startup current) that they can provide is rather insane. Even my small motorcycle battery provides over 250 CCA.
  - elintknower 2y ago
    Super capacitors / just large capacitors in general might eventually save the day here. The only issue is super capacitors can't generally bake in the heat all day and still work for 3-5 years like lead acid batteries can. Supercaps is how "fast" charging in most smartphones works as well since they can soak current faster than the battery itself and also mitigate cycling batteries too hard.

deleted 2y ago

[deleted]

danjl 2y ago

Do kids these days actually make Daisy chains anymore? You know, with real Daisy flowers.

AzzyHN 2y ago
I was unaware that was the origin of the term, so probably not
m463 2y ago
I remember chewing gum wrapper chains made by tricky folding.

elintknower 2y ago

Is anyone else here using Ecoflow batteries as a UPS backup? I really wish Eeaton would produce a similar consumer facing function that is intended to be used long-term 24/7 not just on weekend trips etc.

necovek 2y ago

This is the type of article I find useless. It would be great if Eaton went to the trouble to explain what exact conditions the two UPSes need to fulfill to be successfully daisy chained, which would probably put people away from doing it anyway. But it would also be a much more informative article, and also positively framed, which is always a much better read.

deadbunny 2y ago
That just leads to "I followed your instructions on your website and my house burned down". No company is going to open themselves up to that.
- necovek 2y ago
  I know US is very litigious, but I am certain there are plenty of knowledge-based articles by companies in the US of A that could theoretically be tested in court this way, but really, aren't. I mean, look for any mention of "slow-roast it for 12 hours" in your favourite web search engine (I notice a couple of those say "overnight", yikes).
zootboy 2y ago
They don't explain it because it basically never makes sense to daisy-chain a UPS. If you want redundancy in your power supply chain, use a dual-PSU computer. If you want longer backup times, get a UPS with a bigger battery.
- BuildTheRobots 2y ago
  The only time I think it makes sense if if you're doing a belt+braces with colo'd stuff in a datacentre. The DC will have its own UPS system, but in the event it all goes wrong (which happens more often than I'd like) you probably want something in your cab that can give your equipment notification and time to shut down safely, and provide surge suppression and maybe some level of isolation from the inevitable back-emf caused by the rest of the hall going dark.
- 2y ago

dusted 2y ago

Interesting. I'm sure it's correct, but it makes me wonder about the output quality of these devices. If the output of an UPS is so significantly different from regular utility power that it's unsuitable as input for an UPS, then it must be of a worse quality and unsuitable for the expensive equipment it's supposed to power ? I do understand the logic that chaining UPS will cause interesting things to happen when power is restored and the downstream UPS can then overload the upstream UPS because it will incur additional load when charging its battery, which could trigger overload protection in the upstream device.