Where does the load go on this DC circuit breaker?

[Mattb4]

"Define small amount?"

Now you are getting into areas that testing of individual breaker designs would have to be done. Is 10% back current acceptable? 60%? I have neither the results of lab testing nor any personal experience that could qualify to definitively answer.

 

[RCinFLA]

A humid, salty air, environment is toughest on PV breaker.

DC creates electrolysis migration when metal with a DC potential across various connections is subjected to a humid electrolyte rich environment. Causes metal dendrites to be grown across different DC voltage potential metal terminals. Creates greenish-blue crud which is from tin-nickel-copper metals. Nickel is most inert (gold plating would be best but rarely used) which is often used as surface plating to provide a barrier.

When you open a PV panel junction box on back of panel, say to check bypass diodes, be aware closing it back up in a humid environment will trap humid air inside junction box. Best to flush it out with dry nitrogen just before putting lid back on. At minimum, blow it out with compressed air which has had most of the humidity squeezed out of the air.

It is surprising how much moisture is in just a small amount of air volume. I have opened PV panel junction boxes to find about 0.5 ml of water condensed in corner of plastic box.

 

[Sleeper85]

@RCinFLA

I always enjoy reading your messages, it’s always very informative.

Thank you for this interesting information.

 

[Sleeper85]

Out of curiosity I dismantled a TOMZN MCCB breaker of 200A.

I created a new dedicated topic.

Chinese MCCB - As-built, polarized or not?

Out of curiosity I dismantled a TOMZN MCCB breaker of 200A. There is nothing written on the box indicating polarity to respect. Upon closer inspection of the extinguishing cages I discovered that they were each magnetized in a different direction which indicates that this breaker is...

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