Dual pole DC breaker on + side

[dddem]

So I have this 63A dual pole DC breaker and I want to make it a 126A breaker to protect the positive side only.

Can I wire it like this to achieve the intended effect? (wires coming from + pole of the battery)

 

[Goboatingnow]

No , cause you can’t be sure how the current will split up.

 

[dddem]

No , cause you can’t be sure how the current will split up.

Assuming same length and gauge wire and decent crimps, it should be close imo?

 

[John Frum]

Here is your proof of concept.

Nader DC Circuit Breaker | 60V 200Amp

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[John Frum]

Make sure the breaker is non-polarized.

 

[Goboatingnow]

Assuming same length and gauge wire and decent crimps, it should be close imo?

You can’t be sure and hence you could subject the breaker to over it’s rated capability

 

[dddem]

Make sure the breaker is non-polarized.

It is polarized, as per the schematic that is printed on it. Which is why I want to wire it that way.

 

[dddem]

You can’t be sure and hence you could subject the breaker to over it’s rated capability

I can wire it that way and put a test load on it and measure that the currents are approximately equal with an ampmeter.

 

[John Frum]

It is polarized, as per the schematic that is printed on it. Which is why I want to wire it that way.

Batteries support bi-directional current flow.

"Polarised DC circuit breakers use a small magnet to direct the arc away from the contacts and up into the arc shoot and arc disrupter cage. If the direction of current flow through the unit is reversed, then the magnet directs the arc away from the arc shoot and into the mechanism of the unit thus destroying it. This discussion paper details: (i) the common mistakes installers are making when wiring the polarised breakers; (ii) how the polarised breakers work and how they are wired correctly. The main difference between polarised and non-polarised breakers is that the polarised breakers will typically have a marking on them showing a ‘+’ and ‘–‘ symbol." -- http://greenforcesolar.com.au/wordp...of-Double-Pole-DC-Breakers-LVL2-131210-v2.pdf

 

[dddem]

Batteries support bi-directional current flow.

"Polarised DC circuit breakers use a small magnet to direct the arc away from the contacts and up into the arc shoot and arc disrupter cage. If the direction of current flow through the unit is reversed, then the magnet directs the arc away from the arc shoot and into the mechanism of the unit thus destroying it. This discussion paper details: (i) the common mistakes installers are making when wiring the polarised breakers; (ii) how the polarised breakers work and how they are wired correctly. The main difference between polarised and non-polarised breakers is that the polarised breakers will typically have a marking on them showing a ‘+’ and ‘–‘ symbol." -- http://greenforcesolar.com.au/wordp...of-Double-Pole-DC-Breakers-LVL2-131210-v2.pdf

Yes I agree but a catastrophic discharge current (short circuit on the load side) seems a lot more likely than a catastrophic charge current (other than maybe from lightning, which the PV circuit should be protected against)?

 

[John Frum]

Yes I agree but a catastrophic discharge current (short circuit on the load side) seems a lot more likely than a catastrophic charge current (other than maybe from lightning, which the PV circuit should be protected against?

I see your point.

 

[John Frum]

I see a second battery on your bench.
Are these two batteries to connected in parallel?
If yes and one of them has an internal short, the shorted battery will see big current in the wrong direction.
The other battery's OCPD should trip though.
A melted breaker is better than a venting battery.

 

[dddem]

I see a second battery on your bench.
Are these two batteries to connected in parallel?
If yes and one of them has an internal short, the shorted battery will see big current in the wrong direction.
The other battery's OCPD will trip though.
A melted breaker is better than a venting battery.

True and very good point.

Are class T fuses non-polarized?

 

[John Frum]

@ddem do you know of a primer on the diagrams breakers?

True and very good point.

Are class T fuses non-polarized?

To the best of my knowledge yes.

 

[dddem]

I see a second battery on your bench.
Are these two batteries to connected in parallel?
If yes and one of them has an internal short, the shorted battery will see big current in the wrong direction.
The other battery's OCPD should trip though.
A melted breaker is better than a venting battery.

Although it could be argued that the directional breaker on the good battery would prevent its discharge into the shorted one...

Non polarized dc breakers seem hard to come by.

 

[John Frum]

Although it could be argued that the directional breaker on the good battery would prevent its discharge into the shorted one...

Yes it could and I did

Non polarized dc breakers seem hard to come by.

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[chess-equality]

Non polarized dc breakers seem hard to come by.

For MCBs it might be; MCCBs (molded case) are usually non-polarized (but more expensive).

This one's got 20kA breaking capacity:

https://www.amazon.com/Suntree-2-Pole-Circuit-Breaker-Off-Grid/dp/B09JS22RJC

Suntree DC 160A MCCB Molded Case Circuit Breaker

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www.mcbcircuitbreakers.com

 

[dddem]

I live in Asia so most of the stuff we get is Chinese. Many DC MCB say "non polarized" yet they show + and - symbols on the schematic so what gives!?

Example here:

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[chess-equality]

I live in Asia so most of the stuff we get is Chinese. Many DC MCB say "non polarized" yet they show + and - symbols on the schematic so what gives!?

Me too; I think the polarity can be checked by a meter.

Mine's got "1-2-3-4" markings and no polarity symbols, also doesn't say in the manual.

 

[chess-equality]

Got two of these and in one, in the left side I wired negative; positive in the other; depending on the orientation of my inverters.