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ekstra   ara
 Post subject: Fire Pump Panel
PostPosted: Mon Jul 26, 2010 11:41 am 

Joined: Fri Jan 08, 2010 5:55 am
Posts: 8
Location: NH
After doing a handfull of studies now, I am starting to see a trend with extremely high HRC levels for our Fire Pump Panels. While trying to mitigate these levels I am aware of the following limitations in the code:
695.5 Transformers
1. The transformer must be sized to at least 125 percent of the sum of the loads. (Fire Pump MTR plus Jockey Pump)
2. The transformer primary overcurrent device must be at least a specified minimum size.
3. The transformer secondary must not contain any overcurrent devices whatsoever.
With this in mind, I have no my wiggle room for recommendations to lower these findings.
Has anyone else seen this trend on Fire Pump Panels? Is there a way to mitigate the AF without comprimising the integrity of the Fire Pump system.

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PostPosted: Tue Jul 27, 2010 7:41 pm 
Sparks Level

Joined: Tue Feb 24, 2009 7:05 am
Posts: 252
(I'm from Canada, code requirements will certainly vary)

Could you install a 1:1 isolation transformer between your step-down transformer and the load? Such a transformer is sometimes used to lower the bolted fault current when equipment wasn't properly chosen (AIC rating) to begin with, so I guess it could be used also to reduce the arc fault current (I know: lower current may lead to longer opening time, so YMMV).

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