5 ms·

> I live in a place where blackouts are very infrequent (perhaps a couple per year), but occasionally the mains drops out for only a second or two. I suspect t

by kop316 6y ago

> I live in a place where blackouts are very infrequent (perhaps a couple per year), but occasionally the mains drops out for only a second or two. I suspect these very short dropouts occur when substation switchgear operates, but have no way of being sure. Anyway, with a server running 24/7 I obviously wanted protection against any loss of the mains supply. > So I thought I had covered all bases, and, indeed, the UPS proved useful on several occasions. I would quite often be on a work trip and receive an e-mail from the server informing me that mains power to the UPS had been lost, then another e-mail soon after informing me that mains power to the UPS had returned. Only once did the power cut last longer than the battery capacity, and the server was shutdown automatically. It sounds like the UPS is doing exactly what he wants it to do. This is exactly why I bought a UPS. I would have power transients sometimes and rebooting my entire network (with NAS and servers) was annoying, and I didn't want it to go out when I was gone. His main complaint is he bought a standby UPS where the battery failed, it turned off the UPS (which is understandably frustrating), and now replaces the battery every three years. Looking at the white paper referenced, it even says to go for Line Interactive for servers. I'm also curious how the person knew that power wasn't cut when he was away? So other than buying the wrong type of UPS (which at face value looks to be a valid complain based on research)....why isn't a UPS as useful as they'd think?

xxpor 6y ago
>a standby UPS where the battery failed, it turned off the UPS I assume this would be because the power is always flowing through the battery/inverter? Wouldn't that kill the battery a lot faster? Although it'd make the switch from mains to actual battery power basically a non-event from the output's perspective. Now that I think about it, going 120/240->low voltage dc->120/240->12/5/3.3 is incredibly silly. IIRC there are 48 (or -48?) DC power supplies out there, mostly for data center use. Does anyone make an ATX version that you could hook up to a UPS that has a DC output?
- snuxoll 6y ago
  Standby UPS topologies like the APC Back-UPS lines keep the battery out of the loop until a loss of power from the AC input is detected, at which point the inverter kicks on the the transfer switch takes the feed from there. This is a design choice from APC, money is on the control electronics being powered off the battery meaning a dead or missing battery means the entire unit is non-functional. Making the unit resilient to this probably costs as much as a line-interactive unit, however, so you might as well just tell people to get a better unit than make a middle-ground solution.
  - formerly_proven 6y ago
    I have a line-interactive APC and it most definitely is just a UPS-shaped brick without a battery. Might have changed in newer models, I wouldn't know.
    - zaarn 6y ago
      My APC BackUPS Pro (supposedly line interactive) runs fine without battery (ran it with a tab from shipping still in the case), might depend on the setup. Generally line interactive makes little sense why it wouldn't work without battery since the power rail is shared.
- jcrawfordor 6y ago
  Using a DC auxiliary power supply for backup is common in telecommunications equipment and by extension common in network appliances - "redundant power supply" for network equipment typically means a built-in AC power supply and then DC connections for an external aux power supply that provides battery, often called an RPS. This isn't common for servers though which, if equipped for redundant power, have two AC power supplies. I think this just comes down to the higher current draw usually associated with servers, running even 48VDC power can become costly and impractical when you need to supply say a couple thousand watts per rack, so the extra space and thermal load of an AC power supply in each unit becomes preferable. The downside is that while redundant power supply is usually a "standard" feature on switches and routers (that is, they always have the connection whether or not you buy an RPS is up to you), you need to specify and pay extra for dual AC power supplies up-front in servers, so you don't get as smooth as an upgrade path. That said in datacenter environments you often buy servers, racks, and power systems all at once so it's not as much of a concern. There's a similar tradeoff that exists around bottom-of-rack UPS and central (building or area) UPS---bottom-of-rack UPS tends to be more expensive, higher maintenance, higher thermal load, etc for large installations, so usually large installations use one (or two for A+B power) large central units which may be hybrid between different technologies like flywheel and battery (and you could view the transfer to generators as a "third stage" of a central UPS system), but it also makes your cabling a little more complicated and you have a bit of an "eggs in one basket" situation. Central UPS generally have internal redundancy so their risk of failure is low, and often a bypass device where if a non-recoverable failure of the UPS is detected a contactor "shunts" the entire UPS removing it from the circuit so you don't lose power due to a UPS failure, but that doesn't necessarily save you when the HVAC pours water directly into the UPS control cabinet causing widespread failure of the control electronics... a situation that I have somehow seen twice. I bet on bigger installs you can get an external bypass with some sort of health monitoring though? If HP/Tandem taught is one thing it's that you can always through more redundancy into your very special basket.
Ndymium 6y ago
As a person who has never bought a UPS, this behaviour of turning off power when the battery dies even though there is mains power is unintuitive, and I would have most likely hit the same issue. I see the post title as a PSA, in that if you happened to buy a standby UPS without knowing better, it might not be that useful if you very rarely have power interruptions but the battery keeps dying every couple of years.
- kop316 6y ago
  Trust me.....having infrequent power outages like that are very very annoying. Everything turns off and I have to spend a non-trivial amount of time bringing my network back up (first router, then NAS (encrypted to I need to hand jam in the key), then servers that depend on NAS (also encrypted)). What eventualy got me to get a UPS was during a storm, it happened twice within an hour! This isn't even talking about if I were away, now my servers are down and I have to do it when I get home. That UPS was well worth it to put a stop to that happening.
bluedino 6y ago
>> His main complaint is he bought a standby UPS where the battery failed, it turned off the UPS As a small business network/systems admin, I've had more failed UPS's bring things down than I can count. It's very common.
- kop316 6y ago
  Heh, interesting. Is it a specific brand or model (i.e. I get what I pay for), or this just a thing with UPSes?
- Covzire 6y ago
  I ran into an extremely perplexing problem a few years ago where shutting down one server connected to a UPS would kill the entire network until the server was brought up again. The server was not providing any kind of networking at all, no DNS, DHCP, routing, etc. After wasting a lot of time remotely trying to diagnose this, it was obvious what was happening once I got on site. It turned out that once this server was shut down, the UPS didn't have enough power draw to power the other equipment attached to it, so a switch that was plugged into the same UPS would shut down as well. For some reason it had failed in such a way that it required a certain level of draw for it to function at all.
  - Zancarius 6y ago
    That reminds me of a "feature" in many of the consumer grade UPS units on the market now. I don't think it's enabled by default, but they do have an option to power down the UPS when the primary outlet is no longer seeing any power consumption.
  - jaywalk 6y ago
    Some UPSes have a special outlet on them that when it's not drawing power, it intentionally shuts off the other ports. It's meant for power saving, but I've seen more than one person get tripped up by this functionality.
michaelt 6y ago
> I'm also curious how the person knew that power wasn't cut when he was away? Most homes have something with a mains-powered, non-battery-backed clock. You get home and the microwave or the oven is flashing 12:00 and you know there was a power cut. > So other than buying the wrong type of UPS This isn't a failure of 'type' of the UPS - it's a design fault deliberately left in by the device manufacturer for market segmentation. It would be trivial for them to keep the power outputs on if the battery failed but the mains remained on. Leaving it out is a business decision, hobbling their home product so it doesn't steal market share from their small-business product.

by kop316 6y ago

xxpor 6y ago

>a standby UPS where the battery failed, it turned off the UPS I assume this would be because the power is always flowing through the battery/inverter? Wouldn't that kill the battery a lot faster? Although it'd make the switch from mains to actual battery power basically a non-event from the output's perspective. Now that I think about it, going 120/240->low voltage dc->120/240->12/5/3.3 is incredibly silly. IIRC there are 48 (or -48?) DC power supplies out there, mostly for data center use. Does anyone make an ATX version that you could hook up to a UPS that has a DC output?

snuxoll 6y ago
Standby UPS topologies like the APC Back-UPS lines keep the battery out of the loop until a loss of power from the AC input is detected, at which point the inverter kicks on the the transfer switch takes the feed from there. This is a design choice from APC, money is on the control electronics being powered off the battery meaning a dead or missing battery means the entire unit is non-functional. Making the unit resilient to this probably costs as much as a line-interactive unit, however, so you might as well just tell people to get a better unit than make a middle-ground solution.
- formerly_proven 6y ago
  I have a line-interactive APC and it most definitely is just a UPS-shaped brick without a battery. Might have changed in newer models, I wouldn't know.
  - zaarn 6y ago
    My APC BackUPS Pro (supposedly line interactive) runs fine without battery (ran it with a tab from shipping still in the case), might depend on the setup. Generally line interactive makes little sense why it wouldn't work without battery since the power rail is shared.
jcrawfordor 6y ago
Using a DC auxiliary power supply for backup is common in telecommunications equipment and by extension common in network appliances - "redundant power supply" for network equipment typically means a built-in AC power supply and then DC connections for an external aux power supply that provides battery, often called an RPS. This isn't common for servers though which, if equipped for redundant power, have two AC power supplies. I think this just comes down to the higher current draw usually associated with servers, running even 48VDC power can become costly and impractical when you need to supply say a couple thousand watts per rack, so the extra space and thermal load of an AC power supply in each unit becomes preferable. The downside is that while redundant power supply is usually a "standard" feature on switches and routers (that is, they always have the connection whether or not you buy an RPS is up to you), you need to specify and pay extra for dual AC power supplies up-front in servers, so you don't get as smooth as an upgrade path. That said in datacenter environments you often buy servers, racks, and power systems all at once so it's not as much of a concern. There's a similar tradeoff that exists around bottom-of-rack UPS and central (building or area) UPS---bottom-of-rack UPS tends to be more expensive, higher maintenance, higher thermal load, etc for large installations, so usually large installations use one (or two for A+B power) large central units which may be hybrid between different technologies like flywheel and battery (and you could view the transfer to generators as a "third stage" of a central UPS system), but it also makes your cabling a little more complicated and you have a bit of an "eggs in one basket" situation. Central UPS generally have internal redundancy so their risk of failure is low, and often a bypass device where if a non-recoverable failure of the UPS is detected a contactor "shunts" the entire UPS removing it from the circuit so you don't lose power due to a UPS failure, but that doesn't necessarily save you when the HVAC pours water directly into the UPS control cabinet causing widespread failure of the control electronics... a situation that I have somehow seen twice. I bet on bigger installs you can get an external bypass with some sort of health monitoring though? If HP/Tandem taught is one thing it's that you can always through more redundancy into your very special basket.

Ndymium 6y ago

As a person who has never bought a UPS, this behaviour of turning off power when the battery dies even though there is mains power is unintuitive, and I would have most likely hit the same issue. I see the post title as a PSA, in that if you happened to buy a standby UPS without knowing better, it might not be that useful if you very rarely have power interruptions but the battery keeps dying every couple of years.

kop316 6y ago
Trust me.....having infrequent power outages like that are very very annoying. Everything turns off and I have to spend a non-trivial amount of time bringing my network back up (first router, then NAS (encrypted to I need to hand jam in the key), then servers that depend on NAS (also encrypted)). What eventualy got me to get a UPS was during a storm, it happened twice within an hour! This isn't even talking about if I were away, now my servers are down and I have to do it when I get home. That UPS was well worth it to put a stop to that happening.

bluedino 6y ago

>> His main complaint is he bought a standby UPS where the battery failed, it turned off the UPS As a small business network/systems admin, I've had more failed UPS's bring things down than I can count. It's very common.

kop316 6y ago
Heh, interesting. Is it a specific brand or model (i.e. I get what I pay for), or this just a thing with UPSes?
Covzire 6y ago
I ran into an extremely perplexing problem a few years ago where shutting down one server connected to a UPS would kill the entire network until the server was brought up again. The server was not providing any kind of networking at all, no DNS, DHCP, routing, etc. After wasting a lot of time remotely trying to diagnose this, it was obvious what was happening once I got on site. It turned out that once this server was shut down, the UPS didn't have enough power draw to power the other equipment attached to it, so a switch that was plugged into the same UPS would shut down as well. For some reason it had failed in such a way that it required a certain level of draw for it to function at all.
- Zancarius 6y ago
  That reminds me of a "feature" in many of the consumer grade UPS units on the market now. I don't think it's enabled by default, but they do have an option to power down the UPS when the primary outlet is no longer seeing any power consumption.
- jaywalk 6y ago
  Some UPSes have a special outlet on them that when it's not drawing power, it intentionally shuts off the other ports. It's meant for power saving, but I've seen more than one person get tripped up by this functionality.

michaelt 6y ago

> I'm also curious how the person knew that power wasn't cut when he was away? Most homes have something with a mains-powered, non-battery-backed clock. You get home and the microwave or the oven is flashing 12:00 and you know there was a power cut. > So other than buying the wrong type of UPS This isn't a failure of 'type' of the UPS - it's a design fault deliberately left in by the device manufacturer for market segmentation. It would be trivial for them to keep the power outputs on if the battery failed but the mains remained on. Leaving it out is a business decision, hobbling their home product so it doesn't steal market share from their small-business product.