Tripped breaker, why

DestroyFX

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Hi,
I have a 48V system
I have 1 bipolar DC Breaker (TOB1Z-63A) between my PV and my SCC.
I have another TOB1Z-63A breaker between my SCC and my batteries.
For some reason, the breaker between my charge controller and the battery tripped this afternoon.
Lately we get some clouds so indeed, when the sun go thru, it get over the A I normally get when I have a clear sky

Normally I get about 32A going between the SCC and batteries, but with cloud it go higher of course, today after turning the breaker back on, I had at about 36A.
It is still way far than the 63A rating of that breaker (My SCC is rated for 60A and recommended 63A breaker and I don't expect to really go over 40A)
There is no short or anything like that, everything work just fine, except that the breaker was tripped.
Is there is something I don't know about bipolar breaker? Should I get the 125A flavor or switch to normal one pole model?

I also noticed that the breakers are "warm" while the wire are "coldish"

Screenshot 2022-06-28 153535.png
 

Browneye

Dr. WattSon
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A breaker should be sized 125% of current rating, so 60A X 125% = 75A.
Some of those breakers have directional power thru-put, like bottom to top, or top to bottom, or mixed - and might make a difference when reaching capacity. The link I found says power comes in at the top goes out the bottom.

Otherwise, I have no idea why 30A would trip them. Tripped both legs?

Normally for a SCC just the positive side is put on a breaker for short circuit protection. Generally there wouldn't be an over-current with PV input.
 

FilterGuy

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Some of those breakers have directional power thru-put,
A breaker between the charge controller and the battery should never be a polarized breaker.

The breaker is there to protect from a short circuit anywhere from the battery to the charge controller. (It is not there to protect from current from the charge controller). Consequently, a polarized breaker would have to be installed with the positive toward the battery in order to do it's job. The problem is that this means the current will normally be going backward through the breaker.... and manually flipping a polarized breaker while it has a reverse current is a recipe for disaster. A polarized breaker can not snub the arc of a reverse current so it is likely to have a sustained arc that will cause a fire.

 

FilterGuy

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BTW: I have seen ganged polarized breakers as a way to use polarized breakers with bi-directional current:

Edit: Corrected the diagram
1656455450543.png

The theory is that no matter which way the current is flowing, one of the two breakers will snub the arc and stop the current.

I have never done it this way because it feels 'wrong' to me..... but I can't explain how it is wrong.
 
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DestroyFX

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Well well.
All my batteries cables are 6 except one small patch from the breaker to ground bus that was 8 (like 2 feet). Charts say it's fine up to 10 gauge.

But clearly it got a little toasty in there (see the color, right was breaker end). Did not feel warm probably because I did not notice wen it tripped and it got time to cold down... While the breaker where still warm.

All the other cables copper where still copper color

I just replaced that specific cable with a Gauge 6 cable

Two other pictures are inside breakers box
left = PV-SCC (PV bottom, SCC top)
middle = SCC-BAT (SCC TOP, PV Bottom)
right = Inverter (Bat Bottom, Inverter TOP)

Do these breaker have to be wired always top to bottom or something like that? Which would require to "go around" with the cables. Or it's fine (as FilterGuy said, it's for short protection)

Inverter breaker is underrated for the inverter as it should be 125A according to documentation, (and I plan to replace it) but i'm very rarely using more that 1/4 of that invertor capacity. Even 100% is technically fine as it's a 3000W Inverter, the extra is for surge.

IMG_20220628_171514.jpg
IMG_20220628_171859.jpgIMG_20220628_171921.jpg
 

FilterGuy

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Well well.
All my batteries cables are 6 except one small patch from the breaker to ground bus that was 8 (like 2 feet). Charts say it's fine up to 10 gauge.

But clearly it got a little toasty in there (see the color, right was breaker end). Did not feel warm probably because I did not notice wen it tripped and it got time to cold down... While the breaker where still warm.

All the other cables copper where still copper color

I just replaced that specific cable with a Gauge 6 cable

Two other pictures are inside breakers box
left = PV-SCC (PV bottom, SCC top)
middle = SCC-BAT (SCC TOP, PV Bottom)
right = Inverter (Bat Bottom, Inverter TOP)

Do these breaker have to be wired always top to bottom or something like that? Which would require to "go around" with the cables. Or it's fine (as FilterGuy said, it's for short protection)

Inverter breaker is underrated for the inverter as it should be 125A according to documentation, (and I plan to replace it) but i'm very rarely using more that 1/4 of that invertor capacity. Even 100% is technically fine as it's a 3000W Inverter, the extra is for surge.

View attachment 100488
View attachment 100490View attachment 100489
If I followed the discription, this is what you have:

1656457142531.png

Those are polarized breakers and are inappropriate for all 3 uses. (In all three cases the breaker could be opened while in a reverse current situation). (I am assuming the inverter also has a charge function).

BTW: I looked up the data sheet and found this on the last line in the sheet:

1656457628084.png

The translation is poor but the message is clear.
 

DestroyFX

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If I followed the discription, this is what you have:

View attachment 100506

Those are polarized breakers and are inappropriate for all 3 uses. (In all three cases the breaker could be opened while in a reverse current situation). (I am assuming the inverter also has a charge function).

BTW: I looked up the data sheet and found this on the last line in the sheet:

View attachment 100507

The translation is poor but the message is clear.
Inverter is Inverter only. It's a off grid system.

Yes, the translation is not good. The positive is on positive side and negative on negative side. But If there is direction too (like it have to flow from top to bottom or something like that then they are all reverse, except the SCC-> BAT on where it will only draw a very small quantity of power during the night. (And it's the one that tripped during the afternoon).

As I plan to replace the breaker for the Inverter anyway, I might just replace all, any recommendation?
 

DestroyFX

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Messages
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BTW: I have seen ganged polarized breakers as a way to use polarized breakers with bi-directional current:

Edit: Corrected the diagram
View attachment 100492

The theory is that no matter which way the current is flowing, one of the two breakers will snub the arc and stop the current.

I have never done it this way because it feels 'wrong' to me..... but I can't explain how it is wrong.
I think i'm going to do exactly that, after reading more on the net about theses polarized breakers and solar.

Right now my PV breaker is wired "upside down". But... if the SCC short then the PV would not provide the required Current to trip the breaker anyway. On the other hand, if the solar array short and the SCC get upset and send battery current to PV, the upside down PV breaker would not be "upside down" in that case and do is job properly

For the battery, it's plugged in "correct direction" for normal flow. But if the SCC short, then it will become "upside down"...

Inverter breaker is definitely really upside down as there is no way that the inverter can provide current to the battery.

That or... Putting fuses on my inverter connectors and on the output of the SCC and let them do the job of cutting the circuit under overcurrent protection

At least I did not get any smoke going out far (I use them for disconnect and did it over twenty time so far and many time with over 10 or 20A load)

I assume I can use the one I currently have and wire them like that, right? And Just protect the "Positive" cable... Or getting a bigger box and putting twice the amount of breaker to be able to protect both side.
1656568008985.png
 
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Bud Martin

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Can you check the DC Voltage drops on the breaker to see how much power (Vdrops x Current = Power) it is dissipating when you have high current flow?
 

FilterGuy

What, me worry?
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I think i'm going to do exactly that, after reading more on the net about theses polarized breakers and solar.

Right now my PV breaker is wired "upside down". But... if the SCC short then the PV would not provide the required Current to trip the breaker anyway. On the other hand, if the solar array short and the SCC get upset and send battery current to PV, the upside down PV breaker would not be "upside down" in that case and do is job properly

For the battery, it's plugged in "correct direction" for normal flow. But if the SCC short, then it will become "upside down"...

Inverter breaker is definitely really upside down as there is no way that the inverter can provide current to the battery.

That or... Putting fuses on my inverter connectors and on the output of the SCC and let them do the job of cutting the circuit under overcurrent protection

At least I did not get any smoke going out far (I use them for disconnect and did it over twenty time so far and many time with over 10 or 20A load)

I assume I can use the one I currently have and wire them like that, right? And Just protect the "Positive" cable... Or getting a bigger box and putting twice the amount of breaker to be able to protect both side.
View attachment 100685
I don't see anything terribly wrong with the concept but like I said in my post.... I have never done it that way.

The other thing is "Why are they getting warm?" The polarity issues are not why the breaker popped in the first place.
 

DestroyFX

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Messages
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@Bud Martin @FilterGuy

I did some reading :

Dissipation would be around 2ish watts wight now.
It's ~0.035v difference (per poles) while I have 29.5A, I did test earlier with only ~10A and it was about ~0.02v per pole

Right now breaker is less warm that when I got the thermal disconnect two days ago.

TESTS
~10A
Diff on positive pole and negative pole are ~0.02V

29.6A
Diff on positive pole is 0.034V
Diff on negative pole is 0.036V
Dissipation is ~2W

32A.
Diff on positive pole is 0.038V
Diff on negative pole is 0.04V
Dissipation is ~2.5W

33.1A
Diff on positive pole is 0.04V
Diff on negative pole is 0.042V
Dissipation is ~2.7W

38A
Diff on positive pole is 0.044V
Diff on negative pole is 0.046V
Dissipation is ~3.42W

I don't think I will get more current than that today, not enough clouds for that ray reflection current bonus

1656614493459.png
 
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Bud Martin

Photon Sorcerer
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Messages
3,476
I wonder what the contact resistance or power dissipation spec of the circuity breaker is.
I know that the DIN fuse holder has power dissipation spec at full current, I.E> Schneider Electric.
From Schneider website '1 poles (1P), for protection of photovoltaic applications up to 32A/1000V DC. To be used with 10x38mm fuse links up to 32A and dissipation up to 3W. Compact (17.5mm width), it can be used in modular panels, clipping on 35mm DIN rail, connection by screw clamp terminals, padlockable without accessory. Add-on auxiliaries (fuse carrier assembly kits, clip-in markers) are available (to be ordered separately). Sold in lots of 12 units. Multi standards certified (IEC, UL recognized, CSA, CCC, EAC), Green Premium product (RoHS/REACh).'
 
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