208 v 480

[SparksRfun]

I have a fairly large building that is currently wired all with 208V, because the wiring was done probably int he 1950s. If it were being wired today, it would certainly use 480v distribution. THe building is 500,000 sq ft on 4 floors, and several of the floors have 20' cielings. That doesn't count the dome on top, which lofts into the air high enough it needs an airplane landing light.

We are charged with installing a new emergency riser (optional standby system to supply computers and IT equipment) throughout the building. I am concerned that at 208V, we will be strapped with voltage drop problems when we get to the other end of the building.

Currently the voltages in the building are 4160 and 208. 4160 is scheduled to vanish the next time the building is renovated.

Maintenance staff is very sophisticated, they have no problem with higher voltages and 480 or even medium voltage switchgear. The building is a State Capitol, it is going to be continually renovated generation after generatio as things become obsolete.

My question is, in your opinion would it be foolish to introduce 480V into this building, where it never was before, or, ont he other hand, would it be wise to look forward and install a more modern distribution system?

 

[davidbeach]

Sounds like 480V might be an appropriate response, particularly since your 4160V system is not long for this world.

 

[itsmoked]

Will you use any of the old distribution? If so is it rated 600V wire or the 250-300 stuff?

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[SparksRfun]

>Will you use any of the old distribution? If so is it rated 600V wire or the 250-300 stuff? -ItSmoked

No, "Smokey", I'll be picking out particular loads and running new feeders to them, from new panels scattered throughout the building. The new stuff, whether it is 208 or 480, is requested to be on more reliable wiring than the old stuff. It is really a smattering of loads - a receptacle in this closet, a UPS in that closet, a PA system here or a fire alarm panel there, hardly anything over 5KVA.

One other thing about the building - it is State owned, and therefore a City inspector has never darkened their door. One guy joked "The only way to make it comply with code is to shut it off". A complete electrical gut and replacement was recommended in a recent study, and I was looking in one electrical closet and asked the maintenance man "Is there anything in here that is NOT a code violation?" So I am actually very afraid of reusing any of the existing stuff, both because it isn't real safe and because it is all scheduled to be gutted someday when they get the money (or when it starts causing fires, whichever comes first).

 

[jraef]

If it were me, I'd go the 480V route, with an eye on the future as far as conversion. You will still need a 120/208V system for your office loads of course, but use the 480 to get from one side of the building to the other.

Just out of curiosity, what was the 4160V for and why is it going away? Usually that would have been for the HVAC chillers and if they are really big you may not want to go 480V.

 

[SparksRfun]

Jraef Sez

>Just out of curiosity, what was the 4160V for and why is it going away? Usually that would have been for the HVAC chillers and if they are really big you may not want to go 480V.

This building has a separate energy center on another service, so no chillers in the building. The 4160 comes in the building and distributes around to 5 4160:208 unit substations. That's probably how they got around the voltage drop problem with 208. The biggest loads int eh building are some pipsqueak air handlers.

The utility is phasing out all thier 4160, and the 4160 gear in this building is getting very old. The current thinking is they will eventually install a 12KV loop, and feed several 12KV:480 or 12KV:208 transformers. The loop would allow them to increase redundancy, maybe feed from two substations and have automatic transfer to lessen the likelihood of an outage. But that's all in the future.

 

[tinfoil]

Like many other utilities, we used to have a LOT of 4160V system, which is being converted to 12470 or 24940 (25kV).

Many customers choose to install 12470:4160 (or whatever) stepdown transformers and continue to use their legacy private distribution systems. When budgets permit (or loading requirements change), they then convert bits of their old stuff to the local utility's modern voltages.

You can now get 12470:4160 or 24940:4160 three phase padmounts, and I have seen them complete with isolating switches and even revenue metering.

It would allow you to 'stage' your code-complient upgrades overa longer period, and then sell your stepdown to the next customer who is slower to do the same thing.