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Is is possible to use B type RCCB downstream of AC type RCCB

This Configuration can create blinding of upstream products. 
According to the standards on 30mA RCD: 
- Type B will trip between 15 and 30mA of DC earth leakage current 
- Type A don't trip on DC earth leakage current, but it's blinded by DC earth leakage current up to 6mA 
- Type AC don't trip on DC earth leakage current, but it's blinded by all DC earth leakage current. 

So it's forbiden to use AC or A type RCD upstream of B type RCD. 

We use B type RCD for specific loads (speed driver, converter ..); If there is a load creating less than 15mA DC earth leakage current; the B type will not trip 
but all the AC, A type RCD upstream will be blinded and will not detect standard AC earth leakage current. 



 
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