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Title: Backup Power Supply Question
Post by: Jamin Lynch on July 20, 2021, 04:11:20 PM
In items which come with a built-in backup power supply, like sound consoles or stageboxes, would it be best to leave both on so if one goes out there would be a smooth transition, (I assume there would be a smooth transition) or would it be better to use 1 while leaving the backup off? I know by leaving the backup off the system would shut down if the first power supply were to fail. My thinking is by leaving both on would lessen the life of the backup power supply.


Thanks
Title: Re: Backup Power Supply Question
Post by: doug johnson2 on July 20, 2021, 04:48:24 PM
It is my understanding that modern/current power supplies are more likely to fail due to outside factors rather than internal failure.  As such, it makes more sense to me to have one in use and the other unplugged/off as a standby.  If there is a concern that a power supply would "just fail",  and the backup supply needs to be on-line, I would think the best practice would be to either run them both through a isolated and regulated power supply or a true in-line ups.
Title: Re: Backup Power Supply Question
Post by: Mac Kerr on July 20, 2021, 05:14:47 PM
It is my understanding that modern/current power supplies are more likely to fail due to outside factors rather than internal failure.  As such, it makes more sense to me to have one in use and the other unplugged/off as a standby.  If there is a concern that a power supply would "just fail",  and the backup supply needs to be on-line, I would think the best practice would be to either run them both through a isolated and regulated power supply or a true in-line ups.

I would say best practice is to run one of them through the UPS and the second either direct or off another UPS. Using a single UPS on both power supplies is a single point of failure in a device known for failure.

Mac
Title: Re: Backup Power Supply Question
Post by: Brian Jojade on July 20, 2021, 05:22:43 PM
There really is no 100% right answer to the question.  If the power supply were to crap out mid show, you'd lose sound until you connected the backup and fired back up.  If reliability against that scenario is what you are protecting against is what you are going for, then both need to be powered on and running.  With some gear, when both power supplies are active, the load gets shared across the supplies, so each supply has an easier life vs running off of just one.

Now, if your goal is having a backup power supply available to you in the event that something like a power surge takes out the supply, then having the backup disconnected and off makes sense.  Off but still connected is a potential issue, so I'd make sure that it's completely disconnected if you're concerned about that.
Title: Re: Backup Power Supply Question
Post by: Jeff Lelko on July 20, 2021, 07:38:17 PM
I would say best practice is to run one of them through the UPS and the second either direct or off another UPS. Using a single UPS on both power supplies is a single point of failure in a device known for failure.

Mac

That is my philosophy as well.  What complicates things though is that all your critical gear must have either dual power supplies or a hot spare to avoid a dropout in audio.  As example, my dLive Mixrack has dual power supplies but my Yorkville processor doesn't.  Both live in the same rack and both are critical to pass audio.  If my UPS fails the Yorkville goes down and I lose audio even though the dLive is still running.  There are ways to run hot spares to cover this type of scenario but the options get complicated and expensive...quickly.  Hope this helps!
Title: Re: Backup Power Supply Question
Post by: Andrien (No Last Name) on July 20, 2021, 10:19:00 PM
Additional power supply inventory is also good (excluding the one already being used in redundancy), after all the idea of redundancy is that if 1 is failing you could replace it without the system ever shutdown, not about keeping the system running only on 1 power supply. High Availability is costly tho, and the faster the transfer time between HA system usually the costlier it gets. Correct me if i'm wrong.
Title: Re: Backup Power Supply Question
Post by: Scott Helmke on July 21, 2021, 10:03:17 AM
I would think the first thing to do is decide what level of reliability you need for your situation.  Absolutely no loss of audio, or just the ability to restart after a few minutes of switching things around?  What can your client afford?

There used to be a thing about how when one Midas power supply failed, it could take out the other one while doing so.  The reality was that people would never test them separately, and so it was possible for one to have failed weeks/months ago without being noticed.
Title: Re: Backup Power Supply Question
Post by: Tim McCulloch on July 21, 2021, 10:57:26 AM
Additional power supply inventory is also good (excluding the one already being used in redundancy), after all the idea of redundancy is that if 1 is failing you could replace it without the system ever shutdown, not about keeping the system running only on 1 power supply. High Availability is costly tho, and the faster the transfer time between HA system usually the costlier it gets. Correct me if i'm wrong.
No, you are not wrong.

When we talk about *instantaneous* automatic power transfer, or "rain or shine" events - the price needs to double.  Because the amount of either technology or labor and physical assets is not trivial.

Also any client requirements for these things need to be spelled out in the contract, along with the conditions that precipitate the withdrawal of services.
Title: Re: Backup Power Supply Question
Post by: Brian Jojade on July 22, 2021, 08:22:18 PM
No, you are not wrong.

When we talk about *instantaneous* automatic power transfer, or "rain or shine" events - the price needs to double.  Because the amount of either technology or labor and physical assets is not trivial.

Also any client requirements for these things need to be spelled out in the contract, along with the conditions that precipitate the withdrawal of services.

It's generally considered that adding each 9 to your reliability doesn't just double the price. It increases it 10 fold.  So, to increase your system's reliability from 99% of the time to 99.9% of the time costs 10 times as much to get there.

Most local events don't demand that sort of perfect reliability, because the costs can't be justified.  When you start getting into national broadcasts though, even a few seconds of downtime can cost a fortune.
Title: Re: Backup Power Supply Question
Post by: Jeff Bankston on July 23, 2021, 05:58:32 AM
I have 3 with the Midas daisy chain cables. All 3 stay on so if one goes out the rest stay lit like the miniature christmas lights from the 70's. i never had a failure.
Title: Re: Backup Power Supply Question
Post by: Brian Jojade on July 23, 2021, 12:21:10 PM
I have 3 with the Midas daisy chain cables. All 3 stay on so if one goes out the rest stay lit like the miniature christmas lights from the 70's. i never had a failure.

Do you carry an offline spare too?  A power surge could take out all 3 live power supplies, and then there you sit.
Title: Re: Backup Power Supply Question
Post by: Chris Hindle on July 23, 2021, 12:55:58 PM
Do you carry an offline spare too?  A power surge could take out all 3 live power supplies, and then there you sit.
Back in Ye Olde days, it was fairly common to have 2 power supplies on a switcher, but only have one actually plugged in. That way, a supply line "problem" wouldn't take out both supplies.
Chris.
Title: Re: Backup Power Supply Question
Post by: Jared Bartimus on July 29, 2021, 03:57:19 PM
Back in Ye Olde days, it was fairly common to have 2 power supplies on a switcher, but only have one actually plugged in. That way, a supply line "problem" wouldn't take out both supplies.
Chris.

As long as whoever is at FOH checks voltages before hitting the switch and killing the other supply.
Title: Re: Backup Power Supply Question
Post by: Chris Hindle on July 30, 2021, 08:07:42 AM
As long as whoever is at FOH checks voltages before hitting the switch and killing the other supply.
Before "hitting the switch", you would meter the AC supply BEFORE plugging in the second power supply.....
If left to it's own devices, both supplies would be always powered, and the switcher would flip supplies as needed.
Never a good thing with funky power......
Chris.