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| Labeling PDUs by Liebert https://brainfiller.com/arcflashforum/viewtopic.php?f=24&t=695 |
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| Author: | amohammed [ Tue Oct 06, 2009 8:54 pm ] |
| Post subject: | Labeling PDUs by Liebert |
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. |
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| Author: | WDeanN [ Wed Oct 07, 2009 6:20 am ] |
| Post subject: | |
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. |
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| Author: | Vincent B. [ Wed Oct 07, 2009 12:33 pm ] |
| Post subject: | |
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. |
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