Oversized breaker in series with properly sized fuse

[Carultch]

I have an off-grid array with a DC load, that needs ground fault protection and standard OCPD.

The GFCI breaker is sold as a package deal, with a 50A line breaker and a 1A common tied GFCI breaker. I'd like to put the 50A line breaker in series with a 15A fuse, as is the size requried per 1.56*Isc.

If I do this, does the 50A breaker affect the wire sizing and panel max OCPD? Or does the smaller fuse in series override the 50A line breaker?

 

[shortcircuit2]

Not quite sure of the application your describing...but if your fusing your strings at 15-amps, you must have more than 2 strings. Given that you have multiple strings, your PV output circuit conductors need overcurrent protection according to the maximum parallel source circuit currents. Wire size and overcurrent protection will be per this calculation.

A better descrpition of your application would help to answer the question.

 

[pv_n00b]

The 50A breaker in this situation is really just a switch being controlled by the 1A GFDI breaker. Assuming you are not using it as a OCPD to protect something just treat it like a switch and size everything based on the 15A OCPD rating. But, I'm not sure why you are using the 15A OCPD. If it's only one string feeding a load no OCPD is needed. If it's more than 2 strings and they are being combined you would need multiple 15A fuses.