Correct Label [RE-wrenches]

William Miller wrmiller at charter.net
Fri May 11 13:56:07 PDT 2007


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Drake:

Can you provide a single line drawing and post it to your web site for 
review?  Your verbal description of the power flow was not clear.

William Miller


At 02:35 PM 5/11/2007, you wrote:


>Hi Wrenches,
>
>There is a safety issue with the labeling for a system we are working on, 
>where taps are placed on a 120/208 volt panel, ahead of the main 
>breaker.  These taps are for the purpose of feeding the inverter output to 
>the grid while providing a PV disconnect.
>
>Since the tap is terminated in a small breaker box outside the main 
>breaker enclosure, and located ahead of the main, the PV disconnect box 
>will not be de-energized by turning off the main.  An original solution 
>was to put a label on the box saying "service disconnect," in addition to 
>the label saying "PV disconnect."
>
>However, this arrangement is not a service disconnect.  The service 
>disconnect is a 277/480 volt switch that feeds both a panel, at these 
>voltages, as well as a transformer that feeds the 120/208 panel.  Since 
>the transformer is part of the building's electrical equipment, and not 
>utility equipment, my read is that this main breaker is not a service, 
>even though it supplies different voltages.
>
>How should we label this disconnect box?  We need a way that both insures 
>the safety of people working on the system, and also meets the code 
>requirement.  The label needs to be short due to very tight spatial 
>limitations.
>
>Thanks,
>
>Drake
>
>
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