DIY solar enthusiasts - are you using the correct MCBs on your array?

[Crossy]

Found whilst I was actually looking for something else.

 

What happens when you use an AC breaker on a DC circuit or you use the wrong voltage rating of DC breaker.

 

We want you all around long enough to share your next build with us. Be sure to watch till the end if you think that new 600VDC Schneider (or other brand) charge controller install you‘re doing is no big deal safety wise… we’re talking rubber gloves or rubber bag time people, the choice is up to you.

 

 

Be safe out there!

[Muhendis]

Excellent demonstration.

The reason that almost never happens with a DC breaker is down to the construction of the plastic within the breaker. When a DC breaker opens there is a BIG explosive spark from the contacts. This spark is channeled down a relatively long "tunnel" (measured in centimeters) and dissipates before it reaches the end. The spark always originates from the same electrode and is therefore easy to control. AC breakers don't have such a channel due to the randomness of the spark relative to the sine wave. If you already knew this, stop reading now.

[johng]

Would one of those "old fashioned"  knife switches  be usable ?

 

[Daffy D]

Many years ago I wanted to use a DC switch on an AC circuit just to switch a Hatari fan that had fried electronics.

 

I posted on here about the arcing problem between DC and AC switches but nobody seemed to know what I was talking about.

 

Guess I was ahead of my time. 

Edited July 13, 2021 by Daffy D
Correction

[BritManToo]

I don't use any unnecessary breakers.

My DC breakers are the MC4 connectors on the solar panels.

My AC breaker is the plug the GTI uses to plug into the wall socket.

[Crossy]

2 hours ago, johng said:

Would one of those "old fashioned"  knife switches  be usable ?

 

 

Not that one, it's an AC version. The DC ones have a spring loaded snap action on the knives. I'll see if I can find a photo.

 

 

[Crossy]

1 hour ago, BritManToo said:

My DC breakers are the MC4 connectors on the solar panels.

 

You mean the ones marked "Do not disconnect under load"?

 

[Crossy]

7 minutes ago, Crossy said:

Not that one, it's an AC version. The DC ones have a spring loaded snap action on the knives. I'll see if I can find a photo.

 

Not the best image, but you can see the spring loaded bit. The idea is that it snaps away quickly to break the circuit and arc.

 

[Muhendis]

This ancient DC switch gear vid shows plenty of sparks.