can this breaker be used as a double pole disoconnect

[Samsonite801]

Yup, it'll work fine as a string disconnect, as shown in OP's post or rewired to open both positive and negative leads. Two 150V poles in series, ganged to trip together, will interrupt current the same no matter where each one is in the circuit (so long as in series with the circuit including a fault they might be interrupting.)

When three or more strings are in parallel, I don't believe multiple separate polarized breakers can be relied on. The PV string that is shorted and being backfed trips, but won't interrupt the arc because current is flowing in wrong direction. Ganged with the other two breakers I think it would work. (not the OP's situation.)

Yeah, earlier I had wanted to say I thought it was Hedges who had been the, said: 'reputable poster', who I had thought I heard this confirmation from in another post before, so I had been waiting to see if he would chime in, since I didn't want to accidentally try and drag someone under the bus.

Anyways, thanks for backing my remembrance of that, it does make perfect sense...

 

[Nobodybusiness]

I'm skeptical that 2 150VDC breakers in series can magically tolerate 300VDC.
I would need the magic explained.

That doesn’t make any sense to me.

Just off the top of my head if over amperage occurs then 1 would go then the second but I’m no EE..

They are rated at what they are. Not sure how putting 2 in series double rates them..

Even if you ganged them together wouldn’t one trip the other?

 

[John Frum]

Even if you ganged them together wouldn’t one trip the other?

The handles are connected so one breaker trips the other.

 

[Nobodybusiness]

The handles are connected so one breaker trips the other.

That’s what I’m saying. If one tripped at 150 wouldn’t it trip the other?

 

[SparkyJJO]

That’s what I’m saying. If one tripped at 150 wouldn’t it trip the other?

The breaker does not trip due to voltage, it trips due to current. It is an OCP not an OVP device.

 

[Nobodybusiness]

The breaker does not trip due to voltage, it trips due to current. It is an OCP not an OVP device.

I understand that but if it’s 150 amps and you run 275 amps through 2 150s in series wouldn’t it trip both? I have no idea how 2 150s in series equals 300.

 

[SparkyJJO]

I think you're mixing up your volts and amps on the ratings of the breaker. You're right, wiring two 150A breakers in series won't make them handle 300A. It won't. But we're talking about the voltage rating not the amperage rating. Wiring the two breakers in series with the handles tied together ensures both trip together, which effectively puts only 150V of the 300V across each breaker.

 

[Nobodybusiness]

I think you're mixing up your volts and amps on the ratings of the breaker. You're right, wiring two 150A breakers in series won't make them handle 300A. It won't. But we're talking about the voltage rating not the amperage rating. Wiring the two breakers in series with the handles tied together ensures both trip together, which effectively puts only 150V of the 300V across each breaker.

Yup you’re exactly right. I misread the post completely. Saw breaker and assumed amperage..

Sorry about that..

 

[SparkyJJO]

No problem. Get some coffee

 

[Nobodybusiness]

No problem. Get some coffee

More like sleep. Just got off a 12 hour install.

Night..?

 

[Hedges]

150V + 150V + 150V + 150V = 600V

Product - MidNite Solar

MidNite Solar Product Page.

www.midnitesolar.com

50A + 50A = 100A

Product - MidNite Solar

MidNite Solar Product Page.

www.midnitesolar.com

I would have more concern about current not dividing evenly than voltage. One because the breakers will have headroom to interrupt more voltage, and two because current is going through the breakers in normal operation. If current doesn't divide evenly that isn't a safety hazard (as it would for two parallel wires), but would be a nuisance trip hazard.

It would appear individual breakers are polarized in one or the other direction (by orientation of permanent magnet built in to them.) Opposite directions for OP's picture of series connected, same direction for this higher amperage breaker.

 

[CoolWill]

I'm skeptical that 2 150VDC breakers in series can magically tolerate 300VDC.
I would need the magic explained.

Isn't this just like any two components in series? The voltage rating isn't really important while the contacts remain closed. When they open, an arc is formed, and it's the voltage drop across that arc that is important. Two 150 volt breakers in series is a 300 volt breaker because the total arc gap is double and the voltage drop across each arc is half.

 

[John Frum]

Two 150 volt breakers in series is a 300 volt breaker because the total arc gap is double and the voltage drop across each arc is half.

That is my guess.

 

[cdsolar]

On this again, if the link between the two sides is removed on this 300V device, then I have a 150V double pole breaker that can be used as a DC disconnect for both +/-?

 

[cdsolar]

Well crap, I'm glad this came up, but it throws a wrench...

I purchased a midnight solar 15 amp 300 volt breaker without doing any research. I saw the dual pole and thought I could use it as my "required" DC disconnect.
I've got to be able to disconnect all non grounded conductors. So, both PV positive and negative.

I didn't realize the dual pole was to run the positive through the breaker twice.

I think the breaker would still function and the polarity is correct if I remove the jumper and run it as a dual pole with positive and negative each through one side of the breaker.

The DC PV is about 120 vdc at the coldest VOC, so I'd be fine at the single breaker's 150 volt rating.

@400bird: Did this work?

 

[400bird]

@400bird: Did this work?

Yup, I got right though inspection no prob
But, the inspector was on site for 5 minutes and barely cared to see anything.

 

[cdsolar]

Did this work?

Just talked to midnite tech support and its two 150VDC single pole breakers in series.
So it can't used as a double pole breaker because the string voltage will be too high.

Unless a given string is 150V or under. ?

 

[cdsolar]

Yup, I got right though inspection no prob
But, the inspector was on site for 5 minutes and barely cared to see anything.

My highest voltage after low temperature calculation will be 117V, so I should be ok too.

 

[cdsolar]

FYI Midnite no longer sells the MNEPVXX-300, they now sell MNEPVXX-600-2PP.

https://www.midnitesolar.com/productPhoto.php?product_ID=757&productCat_ID=16&sortOrder=1&act=p#

These breakers also have the removable clip in the bottom and without it it appears to work as a 2-pole breaker, and appears to work just fine as a 2 pole disconnect.