Double Pole Vs Single pole Breakers

[BiduleOhm]

I know what grounding a PV array means and how it works.

What I'm not sure is what you meant. But I'll try an answer anyway: if the fault is before the opened breaker then unless there's a fuse/breaker it'll not be interrupted. If the fault is after the opened breaker then no current can flow since the breaker is open. BTW I'm talking as if you opened the breaker manually to do some maintenance on the SCC for example.

Going to have to make the best of the links too......

Yep, for the others: you need to select and copy the link, and remove [ URL ] from the link to correct it.

 

[tictag]

Ground Fault breakers MEASURE the differential between neutral and ground, if the two are bonded/connected, the differential measurement is screwed up.

GFCI/RCDs measure the difference in current flowing through Live and Neutral (hot/neutral in US parlance). Strictly speaking you don't need an earth for a GFCI to function, but in order to create the current differential, the current has to go somewhere e.g. an independent path to ground.


The links @kernal provided are here:

http://solarabcs.org/about/publications/reports/systemgrounding/pdfs/SystemGrounding_studyreport.pdf

https://www.solarpowerworldonline.c...ess-of-grounding-and-bonding-a-solar-pv-array

https://www.solar-electric.com/lib/wind-sun/PV-Ground.pdf

 

[kernel]

Let's imagine a few cases:

Maybe there's a fault to ground on a panel
Maybe there's a wire from another panel string making contact with this one
Maybe one wire is shorted with an AC wire

Isolating both wires guaranties you can't electrocute yourself.



A breaker is designed to trip even if the handle is blocked (e.g. you can't hold a breaker closed if it doesn't want to because of an over current fault for example) so this will never happen, if one side is stuck the other still breaks. Again double pole is safer than single (what if a single pole get stuck?).

No, it absolutely does not.

 

[kernel]

I know what grounding a PV array means and how it works.

What I'm not sure is what you meant. But I'll try an answer anyway: if the fault is before the opened breaker then unless there's a fuse/breaker it'll not be interrupted. If the fault is after the opened breaker then no current can flow since the breaker is open. BTW I'm talking as if you opened the breaker manually to do some maintenance on the SCC for example.



Yep, for the others: you need to select and copy the link, and remove [ URL ] from the link to correct it.

You cant just read titles, if you read through the material "grounded current carrying conductor" is spelled out.

 

[kernel]

You are not going to help me place my foot in my mouth..... if i dont know, ill say i dont know.

 

[kernel]

Is this because the potential has to be higher to sustain an arc over 2 gaps?

Its because the breakers are polarity sensitive and a fault can be on either side. Lots of home run wire...

 

[kernel]

Its because the breakers are polarity sensitive.

That is all it is with this two pole thing you guys have going......... ahhhhhggggg, thud.

 

[kernel]

The higher the voltage the higher the arc intensity and more likely to weld contacts or be hard to extinguish. We need a conference call with abb or cbi application engineers.

Then the"expert" bone pickers can "expert" all over that guy amd challenge them to some crazy ex3rcise in beating dead horses.

 

[Craig]

Going to have to make the best of the links too......

Just copy the link and paste it in your reply

 

[kernel]

Just copy the link and paste it in your reply

I totally did. Not sure if its a browser issue or what. Links save time and people want a book written on a topic so they dont have to find out for themselves sometimes.... i fear.

That and some just revel in trying to out something someone , damnit, im gonna show'em.....
Kernel dont play that! No more, im going Kurt Kernel!

 

[Craig]

I totally did. Not sure if its a browser issue or what. Links save time and people want a book written on a topic so they dont have to find out for themselves sometimes.... i fear.

That and some just revel in trying to out something someone , damnit, im gonna show'em.....
Kernel dont play that! No more, im going Kurt Kernel!

I appreciate the input and I think this is a real issue that needs to be resolved. I see many schematics out there posted by various equipment suppliers showing double pole breakers. That does not mean they are correct though. I will read all those articles tonight thanks for the link.

Also are you coming from a grid Tied perspective or A totally off grid or does it matter

 

[kernel]

Let's imagine a few cases:

Maybe there's a fault to ground on a panel
Maybe there's a wire from another panel string making contact with this one
Maybe one wire is shorted with an AC wire

Isolating both wires guaranties you can't electrocute yourself.



A breaker is designed to trip even if the handle is blocked (e.g. you can't hold a breaker closed if it doesn't want to because of an over current fault for example) so this will never happen, if one side is stuck the other still breaks. Again double pole is safer than single (what if a single pole get stuck?).

Interesting........ no?

 

[tictag]

I totally did. Not sure if its a browser issue or what.

I believe you copied the links from a Google search page - those links sometime contain elements that Google uses to track 'clicks' (e.g. for businesses that advertise with Google), it's usually best to click the link to go to the page, then copy/paste the address bar URL.

 

[kernel]

I appreciate the input and I think this is a real issue that needs to be resolved. I see many schematics out there posted by various equipment suppliers showing double pole breakers. That does not mean they are correct though. I will read all those articles tonight thanks for the link.

Also are you coming from a grid Tied perspective or A totally off grid or does it matter

Does not matter. If it is grounded pv( most any dc coupled charge controller and many onverters systems) and it is in or on a building you must have ground fault detection at least. Sometimes a breaker will not open, or there may be no overcurrent device, if you switch out the negative a.d a fault does not interrupt the circuit or touch grouded conductive materi out there it will go unnoticed which is much worse than thinking its fine to break both for some kind of safety.

Nec requires it, ground fault detection requires it, proper breaker operation requires it, and.....
I require it. Now have i some wire nutted up, non overcurrent protected non gfd having equipment around in the past amd for temps amd such, freaking god....... absolutely.

We do not though suggest anyone else do, i cannot leave someones house like that, i cannot get a system past inspection like that and i cannot sleep if i have left a potentiay unsafe condition somewhere nor could i suggest anyone ever disregard code where it is a safety issue.

Perfect example. Must provide 100a service to a home...... equipment rated absolute...... sorry inverter for your off grid budget only allows 30A @240vac...... im not going to even bother with trying to comply with that it does not apply.

 

[kernel]

I believe you copied the links from a Google search page - those links sometime contain elements that Google uses to track 'clicks' (e.g. for businesses that advertise with Google), it's usually best to click the link to go to the page, then copy/paste the address bar URL.

When i copy from the search field, i get 'address is hlmlgrou.' Or some other abbreviated non link.

 

[kernel]

Ok so probably an impossible scenario. So say I have a 1 pole breaker on the positive PV line. That breaker is off or open. I then add the positive with the negative somewhere between single pole breaker and panel . what now happens to the negative line connected to my SCC could it have a current spike.

I'm really still as confused as ever. Some say you need them kernel says they make things worse.

What makes things worse. I dont have to have breakers (overcurrent) in 2 or less strings. But if i want to switch the pv array for any reason, and you do need a disconnect, then breakers it is and they are in place in every system i have installed for 12 or more years.

If you have high voltage there likely isnt a choice, under 150vdc the breakers are simply available as singe pole for design (breaker device) purposes whic are beyond the scope of what the average owner or installer needs to know, generally.

It is under the section marked "damnit just use the equipment rated and designed for the purpose"...... now i need to vomit this all away

 

[Dhowman]

Oh my. To anyone searching for a quick answer to this, and a cogent/concise rationale, save yourself some time trying to sort out the back and forth above and check out this single post from an earlier thread. Once you've read it, this reference will make more sense and provide all the detail and breaker specs you're looking for.

 

[upnorthandpersonal]

We need a conference call with abb

I'll see if some of my former students are active in this field at ABB and up for it. They owe me anyway

Once you've read it, this reference will make more sense

I posted that exact reference as well in another thread here that was discussing grounding/earthing in DC. Maybe that and the post you linked to should be a sticky somewhere.

 

[Dhowman]

I posted that exact reference as well in another thread here that was discussing grounding/earthing in DC. Maybe that and the post you linked to should be a sticky somewhere.

That would be helpful to anyone researching how best to ground their DC system and choose the right DC breakers for their application. And, BTW, I stumbled upon that reference by reading your post on the grounding thread, so TY for that one! It's become very clear to me that you can't spec your breakers before figuring out your grounding requirements first.