It is currently Sat Feb 27, 2021 10:58 pm



Post new topic Reply to topic
Author Message
ekstra   ara
 Post subject: Labeling PDUs by Liebert
PostPosted: Tue Oct 06, 2009 8:54 pm 

Joined: Thu Jun 11, 2009 12:38 pm
Posts: 33
Location: Kansas city
Hi

Has anyone dealt with labeling Liebert's Power Distribution Unit (PDUs) or FPCs? These units typically have a 480V main input circuit breaker, a 480/208V transformer and 2 to 4 208V panels (fed from the transformer), all in one cabinet. My dilemma is, do you label all the power panels (each of which has 208V main breaker) by one label indicating the incident energy on the line side of the main breakers or by printing one label for each panel indicating incident energy of the load side of 208V main breaker? I guess I would like to know your approach on labeling this kind of equipment which has multiple incident energies across it.

Following is the link where you will find more info on Liebert's PDU (called PPC now): [url="http://www.liebert.com/product_pages/ProductDocumentation.aspx?id=79&hz=60"]http://www.liebert.com/product_pages/ProductDocumentation.aspx?id=79&hz=60[/url]

Thank you for your time.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Wed Oct 07, 2009 6:20 am 
Sparks Level

Joined: Thu Jul 19, 2007 7:54 am
Posts: 201
Location: St. Louis, MO
amohammed wrote:
by one label indicating the incident energy on the line side of the main breakers


This is my vote, assuming, of course, that the transformer is >125kVA, and that it is all contained in one cabinet. By labeling the line side of the mains, you are looking at the worst case scenario.
I would provide a label for the 480V section, regardless of the 208Y/120V section.


Top
 Profile Send private message  
Reply with quote  
 Post subject:
PostPosted: Wed Oct 07, 2009 12:33 pm 
Sparks Level

Joined: Tue Feb 24, 2009 7:05 am
Posts: 252
Also, verify the IE at the secondary of the transformer (assumed >=125 kVA), when the upstream protection device is on the primary of the transformer.
The longer FCT associated with the lower arc current may give a higher IE.

I just calculated that for kicks for a 125 kVA transfo, and I get a IA (on secondary) which, when reflected at the primary, is about 12 times the nominal current (depending on the upstream fault capacity), just at the border of the INST region (from the TCC of a CB I had close). 85% of that IA can probably push you into the short-term region (depending on your actual primary protection device), where the IE can go up because of time.

My final word: evaluate all different possibilities before putting the label, and use the worst one.


Top
 Profile Send private message  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 3 posts ] 

All times are UTC - 7 hours


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
© 2019 Arcflash Forum / Brainfiller, Inc. | P.O. Box 12024 | Scottsdale, AZ 85267 USA | 800-874-8883