[scubadoo]

6 years ago I went through several cheap(ish) breakers from recognized suppliers (AA, JC etc.) and aliexpress in our setup. They ALL either failed, melted, fell apart or tripped at near half their current ratings within a month or two. A search of this forum would no doubt find a few past comments.

I found these MidNite panel mount circuit breakers and installed several. 40,60 and 100A. Never an overcurrent trip but I have certainly isolated all circuits manually on many occasions.
They all still perform perfectly.

No association etc.
http://www.indepower.co.nz/fuses,-break ... sures.html

[David Wallace]

Because the voltage is below 24volrs AC circuit breakers will work fine. We have used 230vac MCB at work to distribute 24v dc control voltage through out the plant, I work in for 20 years, without any problems. This was even confirmed as ok by an electrical engineer . I'm only talking about 24vbc and below. Why pay big dollars for a DC circuit breaker rated at 270vdc when you are only controling 24vdc! Again I used 230vac MCB to distribute 12vdc through out our caravan without any problems yet. But yes if the intention is to control higher DC voltages above 24vdc then a DC rated circuit breaker is a must.

[Neddy]

David, the problem is arcing between the contact points whenever power is interrupted. DC breakers have special "arc quenching" capability to counteract this. That is why they are more expensive than AC breakers.

Arcing can quickly damage contact points at way less than 24 volts. I can give a nice example of this. I was running a single 12v solar panel into an MPPT controller. Under the test conditions with the panel running at around 18 volts, current was never more than 8 amps. I was using a 10 amp switch to turn the controller solar panel input on and off as I experimented with the setup. That switch burnt out (went open-circuit) in less than a day! Turns out that I had used a 10Amp AC switch. DC switches and breakers are engineered to resist such speedy damage.

Neville.

[David Wallace]

The link below confirms what I have been saying. Schneider Electric MCB are widely used through out NZ and are pretty much the industry standard.
https://www.se.com/nz/en/faqs/FA270748/
Cheers David.

[Neddy]

Schneider Electric make AC only, DC only, and AC/DC circuit breakers. You would want to be sure to get the right one!

As you say, though, "If the intention is to control DC voltages above 24vdc then a DC rated circuit breaker is a must." Just two little 70watt solar panels connected in Series will have a Vmp of over 36 volts and a Voc of 44 volts - well above your arbitrary 24v "threshold".

Logically, though, running a solar array through a circuit breaker is a waste of money. Solar panels are inherently current-limited so can NEVER deliver enough current to trigger any appropriate functional circuit breaker. All you are getting is a very expensive On/Off switch - and even that is unnecessary. In the first RV solar system I ever installed, I connected the solar panels directly to the controller. If I had ever needed to disable the panels, all I had to do was disconnect a single wire right at the controller. 10 years later (!) I did have to do just that when I wanted to replace the original AGM batteries. No switch OR circuit breaker needed!

[Saf5000]

Thanks for the insights guys, I’ve ending up just taking the breaker out and when I visit a jaycar store with a switch il put on of those in. I need the switch because the way the renogy dcc50s works, it limits alternator charging to 25A if any solar input is detected. Sometimes I just want to fast charge 50A from the dc-dc.

Side note in future I may just do away with solar all together just relying on dc-dc charging only. It would free the roof up for a few toys


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