Parallel power feed to Electrical Panel

[logical888]

I have a project in Las Vegas. The Owner is replacing all five (5) ageing & obsolete UPS units (25 kVA each) with a new single UPS. Each UPS feeds an electrical panel with loads that cannot be interrupted during feed UPS change over.
Is anybody has experience feeding electrical panel with two UPS power, one thru normal lugs and the other thru 3-pole circuit breaker (built in the panel)? Is this doable wihout consequences in the electrical loads, i.e., servers computer shutting down.
Thank you for technical help.

 

[masterinbama]

Are you saying you want to parallel the outputs from 2 separate UPS units?
I would stress that the loads on each individual panel needs to be relocated temporarily while the feeder is swapped. I can foresee too many things going wrong otherwise.

 

[iwire]

They need to plan and schedule a shutdown.

Now before you say they can't, yes they can.

Hospitals shut down, data centers shut down, communication centers shut down.

They may not want to, and it may be difficult for them, it may cost them a lot of money, but do not cave in and say you can do this work hot. Think of the out come if it goes badly, how long will they be out then? Who will be expected to pay for the losses?

 

[masterinbama]

They need to plan and schedule a shutdown.

Now before you say they can't, yes they can.

Hospitals shut down, data centers shut down, communication centers shut down.

They may not want to, and it may be difficult for them, it may cost them a lot of money, but do not cave in and say you can do this work hot. Think of the out come if it goes badly, how long will they be out then? Who will be expected to pay for the losses?

That's basically what I'm saying. I have done rolling shutdowns at many government server rooms. Never a problem with proper coordination.
Last one was a 750 KVA ups replacement. total time from removal to power up was 48 hours. Equipment was moved from the UPS to a temp gen set 1 load at a time. IT techs worked around each power down on their end both going down and coming back Went without a hitch.

 

[Shoe]

You will need to have the UPS in maintenance bypass and run a parellel (temporary) feed from the same normal power source ahead of the UPS. Once the new UPS is installed, it will again need to be put into bypass before it can be energized and the temporary feed removed. That is assuming your distribution system will accommodate this endeavor. Something going wrong is certainly not worth the liability in my opinion.

 

[shmojoe]

Just went through the same predicament for a data center UPS (375KVA). Tenant basically thought the world would fall apart if their servers were turned off. After several meetings and "hand holding sessions", we were able to take the data center down in a controlled manner to accommodate the UPS work. Everything came back up and whole DC was running smoothly within 2 hours (of power-up). Basically, it comes down to trading a known for an unknown. Taking the DC systems offline in a controlled manner has issues, but taking the DC down hard (unforeseen problem) has exponentially more risk for all parties involved. Nobody wants to take a DC offline, but very few can afford what it takes to have truly concurrently maintainable infrastructure.

On a side note - say you did parallel two out of phase sources (un-synchronized) at 480v, what would actually happen?

I know it would not be good, but any actual outcome experiences would be appreciated.

ShmoJoe

 

[Shoe]

On a side note - say you did parallel two out of phase sources (un-synchronized) at 480v, what would actually happen?

The two out of phase sources would represent a instantaneous change in voltage corresponding to a very high current... i.e. arc/explosion and probably some injured workers and equipment

 

[sameguy]

Smoke