kW versus Amps

[Anonymous user]

I am a data guy not a power guy.

Our data center has a 60kW Symmetra 80k. It is currently 51% load.

Will I run out of amps even though I have kW left?

We need to add a bunch of new runs to support (5) new Cisco Catalyst 4510's with PoE. Each switch will have dual 6000 watt power supplies that each have dual power connections rated at 20 amp 208v. So, by ratings we need (20) 20 amp connections. Technically, one power cord will be configured as redundant for each switch, so only (15) power connections are really supposed to draw power.

Help? Comments? Questions?

Thanks,
Chris

[Anonymous user]

I am a data guy not a power guy.

Our data center has a 60kW Symmetra 80k. It is currently 51% load.

Will I run out of amps even though I have kW left?

We need to add a bunch of new runs to support (5) new Cisco Catalyst 4510's with PoE. Each switch will have dual 6000 watt power supplies that each have dual power connections rated at 20 amp 208v. So, by ratings we need (20) 20 amp connections. Technically, one power cord will be configured as redundant for each switch, so only (15) power connections are really supposed to draw power.

Help? Comments? Questions?

Thanks,
Chris

[BillP]

hi,


you should move those printers off the UPS, especially if they are laser technology. You might end-up having a bunch of alarms( sometimes battery related) due to that. buy surge protection devices if you want to protect the printers

ciao

[BillP]

Good afternoon,

Every single electrical device has to have a label with the nominal parameters. If not, call the manufacturer for your equipment and ask him.

You have always to consider the nominal electrical values.( which might not be equal to what you actually measure. for example, you box could host 100HDD but you put only 50HDD, still, the electrician will consider your box fully equiped, that means, he calculates the receptacle for your server for its nominal current, even if, you might use, 50%)

Take care,

Mihail

[upsguy_apc]

One thing to consider as you add new load..

The Symmetra PX which you have is a Three Phase UPS. This means that it has three "Hot" legs. Each leg can support 120V Line -Neutral or 208V Line-Line. Your UPS which currently shows 51% load may actually have more than 49% or ~30KW of load available because of the following.

A Symmetra PX with 60KW of available load can support 20KW on each phase. So if each phase isn't balanced properly you will end up showing a higher load level then you actually have..

Example.

Phase 1: 10kw
Phase 2: 2kw
Phase 3: 2kw

Total UPS load: 14kw = 23% actual load out of 60kw

However since Phase 1 is loaded at 10kw the UPS will display a load of ~50%.

It is important that as you add additional load you ensure that each phase gets loaded up properly to avoid overloading a single phase and under utilizing the others.

Now...

Assuming you are currently perfectly balanced at 51% load that means your are most likely utilizing ~30kw of the available 60kw. You plan on adding 5 new switches that each have 6000w power supplies in a redundant configuration. So only 5 of the power supplies should be drawing large amounts of power with the other 5 drawing and low amount of power at idle. So you have a max possible load of ~30KW. Assuming you could add your additional load with unbalancing your UPS(which you can't since your adding 5) your going to push the UPS near overload if these switches are fully utilized. This also doesn't give you any redundancy if a UPS power module was to fail.

Fortunately the UPS you currently have can be expanded by 3 additional power modules for a maximum of 80KW N+1. I'd get in contact with you local APC sales rep to find out about adding the additional modules and explain your current load profile to him. I'd suspect you will need to add 1 more module or 2 to be on the safe side depending on how your currently loaded.

Good Luck!

[Anonymous user]

Thank you for your response and the information. I did find the note about the UPS utilization in one of the documents I found. Phase one is 51%, phase two is in the 4o's and phase three is only 35%. Most of what we have for our actual data center is 3 phase to the racks, but then we have some "large" printers in our print center that are on the UPS. I am guessing that is part of the phase difference problems.


The problems is, I am not feeling the love from APC sales right now.

Chris

Message was edited by: cbabfat

[Anonymous user · Accepted solution]

Follow up question regarding Amps vs. kW.

My three phases say I am at 51%, 42% and 35% load and my amps are at 216 with nominal limits of 222 and maximum of ~270 amps.

What do I do? I have approx. 45% kW to work with, but I am maxed out on output amps. What can I do with my UPS to get more use out of it.

It has been a long and fast two weeks learning all about power. I still need more help! BTW, how can I measure the amps of devices connected to my system that are not on PDU's? (like our SAN)

Thanks,
Chris