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Guidance required on DB Board


KeithR

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Hi all,

My Electrician has wired my DB board as shown in the simplified schematic below.  I note the following:

  1. The grid-feed to the change-over is taken from the output side of Beaker-A.  If there's a need to make the Inverter DB safe, this would need Breaker-A to be off (and the Inverter) which means there is no supply to essential loads during this time.  Shouldn't the grid-feed to the change-over be tied in before Breaker-A?
  2. For the return to the Main DB there is an MCB on the inverter side (#D), then another in the Main DB (#B), and then the change-over.  Is this all necessary?  The cabling is protected by Breaker-D and the change-over is an isolator.  Taking out Breaker-B opens up two DIN rail slots which would help me.

Any thoughts?

Thanks

image.png.41779bf6dcf6d3e98f197c546c1aad2b.png

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30 minutes ago, KeithR said:

Hi all,

My Electrician has wired my DB board as shown in the simplified schematic below.  I note the following:

  1. The grid-feed to the change-over is taken from the output side of Beaker-A.  If there's a need to make the Inverter DB safe, this would need Breaker-A to be off (and the Inverter) which means there is no supply to essential loads during this time.  Shouldn't the grid-feed to the change-over be tied in before Breaker-A?
  2. For the return to the Main DB there is an MCB on the inverter side (#D), then another in the Main DB (#B), and then the change-over.  Is this all necessary?  The cabling is protected by Breaker-D and the change-over is an isolator.  Taking out Breaker-B opens up two DIN rail slots which would help me.

Any thoughts?

Thanks

image.png.41779bf6dcf6d3e98f197c546c1aad2b.png

I am in line with your reasoning on both counts.  But we need to assume that wire/cable thickness as depicted in your drawing are all the same. 

1  technically  feeding the grid bypass from the output of A serves no purpose and its confusing because A is labelled INVERTER. Breaker A serves the purpose of protecting and isolating the inverter grid feed  as it leaves the main box. 

Breaker C  is only there to switch off the inverter in reaching distance from the inverter. Ideally this is an isolator, need not be a circuit breaker. 

2 Breaker D is important as you pointed out and must be a circuit breaker to protect the load cable back to the main box. 

Breaker B  technically serves no purpose at all. 

Other opinions of course are welcome and important. 

 

Edited by BritishRacingGreen
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31 minutes ago, BritishRacingGreen said:

I am in line with your reasoning on both counts.  But we need to assume that wire/cable thickness as depicted in your drawing are all the same. 

1  technically  feeding the grid bypass from the output of A serves no purpose and its confusing because A is labelled INVERTER. Breaker A serves the purpose of protecting and isolating the inverter grid feed  as it leaves the main box. 

Breaker C  is only there to switch off the inverter in reaching distance from the inverter. Ideally this is an isolator, need not be a circuit breaker. 

2 Breaker D is important as you pointed out and must be a circuit breaker to protect the load cable back to the main box. 

Breaker B  technically serves no purpose at all. 

Other opinions of course are welcome and important. 

 

There might be an argument that Breaker B is a convenient point to switch off the incoming inverter output to rest of the main db. I am not 100% sure that this is a COC requirement though. 

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