An STS is more expensive, is only suitable for use when the two supplies are 
phase-synchronized, and typically runs at 99% thermal efficiency.

While UPS power feeds should be phase-syncronized to mains, there are certain 
failure modes where they’ll drift, resulting in A and B losing sync; 
additionally, your colo provider might be powering your rack’s A and B supplies 
from different phases (if not today, then maybe tomorrow - it’s their 
prerogative)

Also: The only reason an STS switches to a replacement supply is if the normal 
supply has failed, so it’s difficult to imagine how that can be a no-break 
operation anyway.

A relay or contactor driven ATS typically has a high MTBF, doesn’t care about 
input phases at all, and runs with the same thermal efficiency as a piece of 
wire.

The break in an ATS is circa 50 mSec, which is well within the endurance of the 
capacitors in the cheapest switch mode power supply you’re capable of buying. 

I’ve never seen IT equipment notice a rack ATS changeover.

  - mark


> On Aug 10, 2017, at 4:24 AM, James Braunegg <james.braun...@micron21.com> 
> wrote:
> 
> Dear All
>  
> Anyone with single power supply devices please do not look at getting an ATS, 
> get a STS !!!
>  
> Short version
>  
> ATS (Automatic Transfer Switch) will typically break power before it makes, 
> thus the connected device could reboot !!
>  
> STS (Static Transfer Switch) will make power before it breaks, providing no 
> break to the power  !
>  
> An example of a recommended device is below
>  
> https://www.vertivco.com/en-asia/products-catalog/critical-power/power-transfer-switches/liebert-lts-63-to-400a/
>  
> <https://www.vertivco.com/en-asia/products-catalog/critical-power/power-transfer-switches/liebert-lts-63-to-400a/>
>  
> Kindest Regards,
>  
> James Braunegg
> <image005.png>
> 1300 769 972 <tel:1300%20769%20972> / 0488 997 207 <tel:1300%20769%20972>
> ja...@micron21.com <mailto:ja...@micron21.com>
> www.micron21.com/ <http://www.micron21.com/>  
> <image006.png> <http://www.micron21.com/>
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> system updates.
> This message is intended for the addressee named above. It may contain 
> privileged or confidential information. If you are not the intended recipient 
> of this message you must not use, copy, distribute or disclose it to anyone 
> other than the addressee. If you have received this message in error please 
> return the message to the sender by replying to it and then delete the 
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>  
>  
> From: AusNOG [mailto:ausnog-boun...@lists.ausnog.net 
> <mailto:ausnog-boun...@lists.ausnog.net>] On Behalf Of Matthew Smee
> Sent: Thursday, 10 August 2017 12:00 PM
> To: ausnog@lists.ausnog.net <mailto:ausnog@lists.ausnog.net>
> Subject: Re: [AusNOG] NextDC Melbourne - Scheduled Power Maintenance - 15th 
> August
>  
> +1
> Every DC agreement I’ve seen (3) have mentioned that you are responsible for 
> supplying it with power and they aren’t responsible if it loses power (i.e. 
> use an ATS). 
>  
> From: AusNOG [mailto:ausnog-boun...@lists.ausnog.net 
> <mailto:ausnog-boun...@lists.ausnog.net>] On Behalf Of Sam Silvester
> Sent: Thursday, 10 August 2017 10:14 AM
> To: Shaun McGuane <sh...@rackcentral.com <mailto:sh...@rackcentral.com>>
> Cc: ausnog@lists.ausnog.net <mailto:ausnog@lists.ausnog.net>
> Subject: Re: [AusNOG] NextDC Melbourne - Scheduled Power Maintenance - 15th 
> August
>  
> If you have single fed equipment in your rack that needs planning before it 
> can be shut down, do you not run a totally forseeable and preventable risk 
> then should that one feed trip?
>  
> This is what ATS are for.
>  
> Sam
>  
> 
> 
> On Thursday, 10 August 2017, Shaun McGuane <sh...@rackcentral.com 
> <mailto:sh...@rackcentral.com>> wrote:
> HI Simon,
>  
> Thank you for your input to the list.
>  
> While you may have provided notifications well in advance, your schedule 
> provided has been changed multiple times and this creates confusion.
> Without asking for further clarification last night I would never have 
> received the following updated schedule from Craig Armstrong today.
>  
> Data Hall 2 – B feed (west/blue PDU side) Tuesday 15th Aug, A feed has been 
> pushed back to later date around November, you will receive official notice 
> once new date confirmed.
> Data Hall 3 –A and B feed has been pushed back to later date around 
> October/November, you will receive official notice once new date confirmed.
> Data Hall 4 –A and B feed has been pushed back to later date around 
> October/November, you will receive official notice once new date confirmed.
>  
> From the latest update today, It appears that most of the works are being 
> postponed for the time being
>  
> Not all devices within racks support 2 feeds and planning is involved with 
> these devices, which is why it is crucial to receive accurate information 
> about any pending outages or upgrades
> to the NextDC DataCentres which affect services.
>  
> Additionally, I have not received these updates via the normal NextDC E-Mail 
> communication method, so I am sure other customers will be wondering whats 
> happening too.
>  
> Happy to have a conversation offline about this feel free to give me a call 
> on my mobile.
>  
> Regards
> Shaun
>  
>  
>  
> From: AusNOG [mailto: <mailto:ausnog-boun...@lists.ausnog.net> 
> <>ausnog-boun...@lists.ausnog.net <mailto:ausnog-boun...@lists.ausnog.net>] 
> On Behalf Of Simon Cooper
> Sent: Thursday, 10 August 2017 8:39 AM
> To:  <>ausnog@lists.ausnog.net <mailto:ausnog@lists.ausnog.net>
> Subject: Re: [AusNOG] NextDC Melbourne - Scheduled Power Maintenance - 15th 
> August
>  
> Thanks guys, appreciate the feedback.
>  
> At NEXTDC we work very hard to keep critical infrastructure maintenance that 
> impacts racks or the environment within the data hall to an absolute minimum.
>  
> However, some works are required to happen from time to time by law and one 
> of those activities is a de-energisation and inspection of each of our major 
> switchboards.  This is all about ensuring that the electrical system is safe, 
> and is an unavoidable piece of work. Rightly so.
>  
> Every rack in a NEXTDC data centre has 2N power feeds offered to it, and we 
> highly recommend that they are used for every device in the rack.  This 
> occasional maintenance is one of the many reasons we provide this capability. 
>  Any device using the 2N supplies (aka A & B feeds) will simply see its power 
> swing from one feed to the other.  Any rack that is drawing no more that its 
> contracted power level will have no issue when all devices move from A to B 
> or vice versa.
>  
> Our notifications were made well in advance, as we want to give customers 
> time to consider the management of these works and we don't assume that every 
> rack is perfectly deployed:  We are here 24/7 to assist customers with rack 
> inspections or specific circuit down tests or maybe a controlled move prior 
> to the day (e.g. for devices that are single fed).
>  
> Also, as we work though those discussions with customers we understand the 
> timing in relation to their businesses, and we work very hard to coordinate 
> schedules despite each switch board supporting many different customers and 
> customer instances across the data centre.  Occasionally that means we have 
> to make a difficult decisions which may result in schedule changes.  When 
> that does happen, we do not compromise our notification periods.
>  
> I'll be happy to discuss these works with anyone - probably best offline or 
> on the phone - but trust me when I say we are doing our absolute best to keep 
> your data centre operating safely and reliably for many years to come.
>  
> Thanks,
> Simon
> COO, NEXTDC
>  
> -----Original Message-----
> From:  <>nat...@nightsys.net <mailto:nat...@nightsys.net>
> Sent: Thu, 10 Aug 2017 05:39:02 +1000
> To:  <>sh...@rackcentral.com <mailto:sh...@rackcentral.com>
> Subject: Re: [AusNOG] NextDC Melbourne - Scheduled Power Maintenance - 15th 
> August
> 
> This seems reasonable? As long as no single Data Hall has both A and B feeds 
> removed simultaneously, that seems normal. Doing B on Hall 2 and A on Hall 3 
> on the same day does seem slightly adventurous, but not entirely unreasonable 
> (mostly in terms of if something goes bad in both, staff get stretched thin 
> remediating issues).
>  
> A and B feeds are designed to provide redundancy to equipment, allowing one 
> feed to fail and systems to continue on the other. Anything mission critical 
> should be able to draw from either feed as required (dual PSU), and if there 
> is a power deficit on one feed (causing circuits to trip), that would imply 
> the circuits are incorrectly sized?
>  
> In addition, anything mission critical with a single power supply would be on 
> an ATS you would assume, or a pair of equivalent devices installed with one 
> on each rail?
>  
> Things break in datacentres, planned maintenance happens sometimes, better 
> than no maintenance at all :) The fact they are notifying you is better than 
> not, and it being scheduled is probably still better than unscheduled :) 
> (easier to ensure sufficient staffing to keep a close eye on things)
>  
> Nathan.
>  
> On Wed, Aug 9, 2017 at 3:43 PM, Shaun McGuane < <>sh...@rackcentral.com 
> <mailto:sh...@rackcentral.com>> wrote:
> 
> Here is the entire scheduled maintenance windows for all the halls we occupy.
> 
>  
> 
> DataHall 2
> 
> A Feed - Tuesday 8th August 2017 07:00 UTC +10 until 16:00 UTC +10.
> B Feed - Tuesday 15th August 2017 07:00 UTC +10 until 16:00 UTC +10.
> 
>  
> 
> DataHall 3
> 
> A Feed - Tuesday 15th August 2017 07:00 UTC +10 until 16:00 UTC +10
> B Feed - Monday 14th August 2017 07:00 UTC +10 until 16:00 UTC +10
> 
>  
> 
> DataHall 4
> 
> B Feed - Tuesday 15th August 2017 07:00 UTC +10 until 16:00 UTC +10.
> 
>  
> 
> ·         So looks like no power on 3 data halls B feeds on the same day. 
> 
> ·         Data Hall 2 was scheduled for A rail on the 8th of August but has 
> been re-scheduled with no new date of works.
> 
> ·         Data Hall 3 was scheduled for A rail on the 
> 
>  
> 
> Problem is that I have 3x separate dates on 3 separate e-mails for Data Hall 
> 3 and I have requested a revised clarification
> 
> Just now on the above as there has already been re-schedules for Data Hall 2 
> and 3.
> 
>  
> 
> This feels like it’s going sideways and it has not even started.
> 
>  
> 
> Regards
> 
> Shaun
> 
>  
> 
>  
> 
> From: AusNOG [mailto: <mailto:ausnog-boun...@lists.ausnog.net> 
> <>ausnog-boun...@lists.ausnog.net <mailto:ausnog-boun...@lists.ausnog.net>] 
> On Behalf Of Murat Sener
> Sent: Wednesday, 9 August 2017 3:20 PM
> To: Matthew VK3EVL < <>hit...@itglowz.com <mailto:hit...@itglowz.com>>;  
> <>ausnog@lists.ausnog.net <mailto:ausnog@lists.ausnog.net>
> 
> Subject: Re: [AusNOG] NextDC Melbourne - Scheduled Power Maintenance - 15th 
> August
>  
> 
> We have been told only Feed B in Data hall 2 will be effected as per original 
> schedule and Feed A is yet to be rescheduled. <>
>  
> 
>  
> 
>  
> 
> <image009.png>
> 
> Murat Sener     Datacentre Manager
> 
> PREMIER Technology Solutions
> P. 1300 76 76 48    F. 1300 76 76 49    M. 0450 604 350 
> 
>  
> 
> How am I doing? Let us know!
> SIMPLY CLICK ON A FACE TO GIVE FEEDBACK 
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> GREAT
> 
> AVERAGE
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> BAD
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> <image012.png> 
> <https://protect-au.mimecast.com/s/krZGBXug3DJiw?domain=crewhu.com>
>  
> 
> From: AusNOG [ <>mailto:ausnog-boun...@lists.ausnog.net 
> <mailto:ausnog-boun...@lists.ausnog.net>] On Behalf Of Matthew VK3EVL
> Sent: Wednesday, 9 August 2017 3:13 PM
> To:  <>ausnog@lists.ausnog.net <mailto:ausnog@lists.ausnog.net>
> Subject: Re: [AusNOG] NextDC Melbourne - Scheduled Power Maintenance - 15th 
> August
> 
>  
> 
> What about both feeds happening on the same day at the same time?
> 
>  
> 
> On 9/08/2017 2:55 PM, Shaun McGuane wrote:
> 
> HI Damien,
> 
>  
> 
> My apologies that’s correct – but isn’t anyone concerned about the works 
> being completed during business hours?
> 
> What about increased loading of the active rail once one of them is switched 
> off for these works?
> 
>  
> 
> Regards
> 
> Shaun
> 
>  
> 
>  
> 
> From: Damien Gardner Jnr [ <>mailto:rend...@rendrag.net 
> <mailto:rend...@rendrag.net>] 
> Sent: Wednesday, 9 August 2017 2:39 PM
> To: < <>ausnog@lists.ausnog.net <mailto:ausnog@lists.ausnog.net>> < 
> <>ausnog@lists.ausnog.net <mailto:ausnog@lists.ausnog.net>>; Shaun McGuane < 
> <>sh...@rackcentral.com <mailto:sh...@rackcentral.com>>
> Subject: Re: [AusNOG] NextDC Melbourne - Scheduled Power Maintenance - 15th 
> August
> 
>  
> 
> It says 7am -> 4pm in what you quoted? (UTC+10 is AEST)
> 
>  
> 
> On Wed, 9 Aug 2017 at 2:36 pm, Shaun McGuane < <>sh...@rackcentral.com 
> <mailto:sh...@rackcentral.com>> wrote:
> 
> HI Noggers,
> 
>  
> 
> Has anyone seen this scheduled maintenance notification happening next week?
> 
> They maybe upgrading feeds or boards throughout the datacentre – has everyone 
> seen this notification of works?
> 
> It appears to be happening starting 5PM through to 2AM AEST for all Datahalls 
> on the same date.
> 
>  
> 
>  
> 
> WHAT:
> NEXTDC M1 Melbourne data centre, with the assistance of specialist 
> contractors, will conduct offline preventative electrical maintenance work on 
> high-voltage and low-voltage main isolators. This will affect A and B feeds 
> to the racks in Data Hall 2/3/4 on the 15th of August.
> 
> WHEN:
> A Feed - Tuesday 15th August 2017 07:00 UTC +10 until 16:00 UTC +10.
> B Feed - Tuesday 15th August 2017 07:00 UTC +10 until 16:00 UTC +10.
> 
> HOW AM I AFFECTED?
> Due to the nature of the work a single feed will be removed as per the dates 
> and times above. We recommend that customers balance the power between both 
> power rails to minimise impact during this period. If you have single feed 
> devices we recommend you:
> 
>  
> 
> Regards
> 
> Shaun
> 
>  
> 
>  
> 
>  
> 
> _______________________________________________
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> VK2TDG. Dip EE. GradIEAust
>  <>rend...@rendrag.net <mailto:rend...@rendrag.net> -  
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