Backfed DC breakers and Line/Load Markings

Discussion about the Power System DC Disconnect (PSDC)

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bluetinc
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Joined: Sun Sep 10, 2006 2:38 pm
Location: Maryland

Backfed DC breakers and Line/Load Markings

Post by bluetinc » Sun Sep 10, 2006 2:54 pm

Hey All,

As I am working through wiring the DC side of my PS2 system I have noticed that the DC breakers are marked with line and load side terminals. This brings up two issues.

1. Many of the outback schematics show the breakers connected in reverse of how they are marked. Are they incorrect?

2. Because the GVFX Inverters can charge the batteries, this gives leads to a true backfed breaker case, in which the NEC states only breakers not marked with Line and Load terminal sides are approved.

Am I missing something here? Is there a statement out there from Outback stating that the breakers were certified in both directions and the line and load labels should not be there?


Peter

Scott Payne

Post by Scott Payne » Tue Sep 12, 2006 10:58 am

bluetinc,
1. Many of the outback schematics show the breakers connected in reverse of how they are marked. Are they incorrect?
Those drawings date from when OutBack used Airpax breakers, which were not marked Line/Load. Recently most breaker manufactures have gone to marking all breakers Line/Load.
2. Because the GVFX Inverters can charge the batteries, this gives leads to a true backfed breaker case, in which the NEC states only breakers not marked with Line and Load terminal sides are approved.
The convention has been that with breakers marked Line/Load that the Line side should be connected to the source with the highest fault current potential. So in the case of battery breakers, Line would be connected to the battery even though the inverter does source power as a charger.

Scott

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