DC Circuit Breaker Fires

[Jennifer]

Further to my earlier post https://diysolarforum.com/threads/amazing-length-of-time-walking-after-a-2300v-arc-flash.28037/ be careful about selecting and wiring DC circuit breakers kids...

Also discussed here but a good reminder: https://diysolarforum.com/threads/dc-circuit-breaker-fires.30544/

 

[D71]

Interesting. thanks for sharing. Breakers should never be used as switches.

 

[ko6kL]

Would I see anything like this on a 47 volt PV system ?

 

[foggysail]

Would I see anything like this on a 47 volt PV system ?

You might! It depends on the circuit's inductance and the flowing current. When a dc circuit is interrupted it can generate a very large voltage that can result in a continuous arc. The basic equation for the voltage is V = L* di/dt where di is the instantaneous current flowing and T is the interrupting time. And in a switching mode, T= 0 or at least approaches 0.

AC does not have that problem because a sinewave has 0 current twice each cycle.

 

[Kornbread]

Looks like a cheap polarized breaker that a lot of people use which uses a magnet to help extinguish the arc. If they flow current in the wrong direction, the magnet cannot do its job and you get a toasted marshmallow. That's why I want a classT fuse between the battery bank and SCC/AIO, and dislike using this type of breaker anywhere current can flow in both directions.

 

[ko6kL]

Looks like a cheap polarized breaker that a lot of people use which uses a magnet to help extinguish the arc. If they flow current in the wrong direction, the magnet cannot do its job and you get a toasted marshmallow. That's why I want a classT fuse between the battery bank and SCC/AIO, and dislike using this type of breaker anywhere current can flow in both directions.

View attachment 129318

Pretty sure current can flow both ways about anywhere in a circuit, PV panel could even short out mid-panel to ground, so flowing backwards on the negative leg right ? Wonder if the magnet works if breaker is sideways or mounted upside down etc??

 

[Nan_wpg]

Interesting. thanks for sharing. Breakers should never be used as switches.

How else are you supposed to,disconnect an array?

 

[Jennifer]

How else are you supposed to,disconnect an array?

Are you being serious?

With a PV disconnect, here, let me Google that for you:

AIMS Power Solar PV DC Quick Disconnect Switch 1600V 64Amp – The Inverter Store

quick disconnect gives your solar system extra safety and flexibility when maintaining your system.

theinverterstore.com

Solar PV Dual Circuit Disconnect - e Marine Systems

Solar PV Dual Circuit Disconnect allows an easy and safe means to turn off/on and disconnecting the vessel solar array.

www.emarineinc.com

https://www.eaton.com/us/en-us/catalog/low-voltage-power-distribution-controls-systems/solar-disconnects.html

What are solar AC and DC disconnects and why do you need them?

Learn more about solar AC and DC disconnects, how to size solar disconnect switches, and why they are essential for a functioning solar panel system.

aurorasolar.com

Disconnect Boxes

Electrical Disconnect Boxes. Solar system electrical disconnects (a/k/a disconnect boxes)? Love em. Gotta have em. In fact, the National Electric Code (NEC), section 690.15, requires arrays to have a disconnecting means to isolate the inverter from the PV power source. Utility grid-tie inverters...

www.solarpanelstore.com

Lorentz PV Disconnect - Solargen

Premium quality PV Disconnect Switch designed for PS2150 – PS24000 pumping units, Simple and cost effective unit, Connects module string, DC rated disconnect switch rated 400VDC and 40A

solargentechnologies.com

Below text is from the resources section (link below), suggest you take some time and read it, it may save your house one day.

Fusing & Wire Sizing guidelines for solar panels

This resource is intended to help the user understand when they need to add Over Current Protection Devices (OCPDs - Fuses or Breakers) to the solar panel array and what size the OCPDs need to be. There is also guidelines for wire sizing for the...

diysolarforum.com

Overcurrent Protection on Solar Charge Controllers and solar arrays

Disconnects Vs OCP on the Output circuit.

All solar installations should have a disconnect on the output circuit, between the solar array and the solar charge controller. This disconnect should disconnect both the positive and the negative line from the array. (This is one of many disconnect requirements that the NEC places on solar installations).

Quite often, the disconnect is implemented using a dual circuit breaker because using a breaker can be a cost-effective way to implement a disconnect. Even some controller manufacturers say to use a breaker. This has created confusion that leads some people to believe breakers are required. However, if the system is installed with proper string OCP (if needed) and properly sized wires, there is not a need for the disconnect on the PV Output circuit to be a breaker. A properly rated dual pole switch is adequate.

If a breaker is used as the disconnect, there are a few things to keep in mind.

• Breakers are not typically designed for frequent use as a switch. Using a breaker as a switch can weaken them over time, and this could result in nuisance trips.
  
• When used in place of a switch, a breaker’s trip rating should be higher than the calculated PV output circuit current
  (PV output current = Isc x number of parallel stings x 1.56 =)
  

 

[Jennifer]

Absolutely serious. I asked because combiner boxes have breakers, presumably used to shut off power (in addition to being a breaker)

no need to be a cunt about it. Fucking cunt

Toughen up buttercup, don't ask questions if you don't want answers, don't read my post, see if I care if you burn your house to the ground. PS, with a name like Nan_wpg I'd be a bit more careful about gender or nationality slurs, it's not welcome here, especially when people are answering YOUR question, dispite that handle virtually begging for it and your comment deserving of it.

 

[Jennifer]

What the hell,are you even talking about? What does my handle have to do with anything? I want answers. Answers without your shit attitude. Take it elsewhere and think before you post. Lesson learned

I've had several people contact me about your inappropriate comments, calling people c*nt (like you did me) when they tried to help you by giving you info you could have easily found in Google is not appropriate and is against @Will Prowse 's code of ethics, not to mention in very poor taste.

Please read!

Official Forum "Code of Conduct" and "Terms of Service"

Code of Conduct Advertising is not allowed. Affiliate links, self promotion, spam etc, will result in a permanent ban and your IP address will be listed. It is ok to post basic links to products you like, but if we find that you are a shill, you will be banned. Posts should stay on topic. If...

diysolarforum.com

 

[rodrick]

Absolutely serious. I asked because combiner boxes have breakers, presumably used to shut off power (in addition to being a breaker)

no need to be a cunt about it. Fucking cunt

Breakers are for over current protection, mag starters/contactors/switches are for turning power sources off
or on
she most likely assumed with over 200 posts that you must have learned something and maybe you were kidding her
she obviously didn’t know that you are a different kind of special with a very foul mouth and I’m sure she is sorry she had no intention to pick on a special needs person

 

[Sunny Days]

What the hell,are you even talking about? What does my handle have to do with anything? I want answers. Answers without your shit attitude. Take it elsewhere and think before you post. Lesson learned

Nan_wpg asked a legitimate question, Most products out there use the same shitty polarised breakers and cant be trusted.​

 

[Jennifer]

Nan_wpg asked a legitimate question, Most products out there use the same shitty polarised breakers and cant be trusted.​

And I gave a legimate answer, (actually I gave several) do you think I deserved his response?

 

[rodrick]

Nan_wpg asked a legitimate question, Most products out there use the same shitty polarised breakers and cant be trusted.​

U are correct there are a lot of crappie breakers out there but breakers are for over current protection not switching or disconnect uses
she gave him many good options and the correct reply should of been thank for the information

 

[Steve Fractals]

I really don't want to burn my house down but surely if you a proper rated 2 pol DC breaker then you should also be able to use that to isolate PV for the odd occasion that you might need to do that, I'm not talking of using this like every day as I don't need to do that so just say once or twice a year or in an emergency which is surely what breaker switches are for.

Are you saying that all DC breakers have this issue or just some of the cheaper ones etc?

 

[Mattb4]

I really don't want to burn my house down but surely if you a proper rated 2 pol DC breaker then you should also be able to use that to isolate PV for the odd occasion that you might need to do that, I'm not talking of using this like every day as I don't need to do that so just say once or twice a year or in an emergency which is surely what breaker switches are for.

Are you saying that all DC breakers have this issue or just some of the cheaper ones etc?

Breakers are appropriate for isolation use. If they were not you would see switches on every distribution panel. In my opinion switches are needed for things that have a repeated need to be switched on or off.

Not sure why people get so passionate about simple things.

BTW, The breakers being destroyed from improper connection wiring and high DC voltage is not an indication that they can not do the job when wired correctly. In fact the video shows them doing so. Never take the wrong lesson from something you encounter.

ETA: Always try to remove loads before operating a breaker.

 

[Bud Martin]

BTW, circuit breaker should also be exercised.

KEN'S KORNER - Testing & Exercising Branch Circuit Breakers | Ken's Korner

www.pducables.com

 

[Jennifer]

Me thinks you have the wrong person. Check again. This is the first time you’ve replied inappropriately to me and received the deserved response.

other than this time I e had ZERO contact with you.

for the record you are the only person o. This forum I’ve called a cunt. Get your facts straight before you spread false information

I was referring to this exchange, no other, you’re disgusting, learn some class.

 

[rodrick]

Breakers are appropriate for isolation use. If they were not you would see switches on every distribution panel. In my opinion switches are needed for things that have a repeated need to be switched on or off.

Not sure why people get so passionate about simple things.

BTW, The breakers being destroyed from improper connection wiring and high DC voltage is not an indication that they can not do the job when wired correctly. In fact the video shows them doing so. Never take the wrong lesson from something you encounter.

ETA: Always try to remove loads before operating a breaker.

I agree they beat pulling fuses I’ve got old panels with fusestat/fusetron and other types and it’s nice to just flip the breaker
the key is as you said “always try to remove loads before operating a breaker”
I look at a breaker more like a emergency kill switch and not for repeated usage as a switch
that’s the point I was trying to make
also Bud has a good point of cycling them on occasion is a good idea

 

[curiouscarbon]

Are you being serious?

With a PV disconnect, here, let me Google that for you:

AIMS Power Solar PV DC Quick Disconnect Switch 1600V 64Amp – The Inverter Store

quick disconnect gives your solar system extra safety and flexibility when maintaining your system.

theinverterstore.com

Solar PV Dual Circuit Disconnect - e Marine Systems

Solar PV Dual Circuit Disconnect allows an easy and safe means to turn off/on and disconnecting the vessel solar array.

www.emarineinc.com

https://www.eaton.com/us/en-us/catalog/low-voltage-power-distribution-controls-systems/solar-disconnects.html

What are solar AC and DC disconnects and why do you need them?

Learn more about solar AC and DC disconnects, how to size solar disconnect switches, and why they are essential for a functioning solar panel system.

aurorasolar.com

Disconnect Boxes

Electrical Disconnect Boxes. Solar system electrical disconnects (a/k/a disconnect boxes)? Love em. Gotta have em. In fact, the National Electric Code (NEC), section 690.15, requires arrays to have a disconnecting means to isolate the inverter from the PV power source. Utility grid-tie inverters...

www.solarpanelstore.com

Lorentz PV Disconnect - Solargen

Premium quality PV Disconnect Switch designed for PS2150 – PS24000 pumping units, Simple and cost effective unit, Connects module string, DC rated disconnect switch rated 400VDC and 40A

solargentechnologies.com

Below text is from the resources section (link below), suggest you take some time and read it, it may save your house one day.

Fusing & Wire Sizing guidelines for solar panels

This resource is intended to help the user understand when they need to add Over Current Protection Devices (OCPDs - Fuses or Breakers) to the solar panel array and what size the OCPDs need to be. There is also guidelines for wire sizing for the...

diysolarforum.com

Overcurrent Protection on Solar Charge Controllers and solar arrays

Disconnects Vs OCP on the Output circuit.

All solar installations should have a disconnect on the output circuit, between the solar array and the solar charge controller. This disconnect should disconnect both the positive and the negative line from the array. (This is one of many disconnect requirements that the NEC places on solar installations).

Quite often, the disconnect is implemented using a dual circuit breaker because using a breaker can be a cost-effective way to implement a disconnect. Even some controller manufacturers say to use a breaker. This has created confusion that leads some people to believe breakers are required. However, if the system is installed with proper string OCP (if needed) and properly sized wires, there is not a need for the disconnect on the PV Output circuit to be a breaker. A properly rated dual pole switch is adequate.

If a breaker is used as the disconnect, there are a few things to keep in mind.

• Breakers are not typically designed for frequent use as a switch. Using a breaker as a switch can weaken them over time, and this could result in nuisance trips.
  
• When used in place of a switch, a breaker’s trip rating should be higher than the calculated PV output circuit current
  (PV output current = Isc x number of parallel stings x 1.56 =)
  

you googled it for them..! ?

 

[DPC]

Years and years ago we used Westinghouse HKD breakers with a thermal magnetic 250 amp trip unit on the little battery locos.
That's breaker rated at up to 400 amps in that frame size, 600 volt AC and an interrupt capacity of 40,000 amps.
All this for a 90 volt loco a couple of small traction motors and battery bank of lead acid that weighed about a ton ( can't recall the ratings on batteries and motors ).

The three phase breaker was on the + DC side of the pack and used to protect the loco in case of a short and as a disconnect mean for the pack when it was removed for charging ( those were a 300 amp 90 volt exide unit as I recall )

The AC K frame breaker was wired so current went in one phase down a jumper connected that to the incoming of the middle phase and the that fed the top of the third phase... ( confused? all three sections of the three phase breaker were wired in series does that sound better ? )

All these little breakers are scary and made in China and some are fakes too.
Fuses only have to work once and they tend to be much more reliable.
Uses fuses for protection and breakers like these little biscuit units as Isolation devices and you will sleep better.

Or buy something expensive, big and proven to do the job

You know what really impressed the hell out of most guys I worked with who ran the trains?
When the power was out I would bring a Loco over and strip the wires off the coffee maker and feed it off the loco battery pack.
At least we had hot coffee while we waited for power to be restored.....

 

[rfbuehler]

Ok rather than starting a new thread I’ll ask here.

I want an breaker on an inverter. I have an expensive big breaker like shown in previous respons. The question I have is depending on weather it is charging or discharging the polarity changes same as the breakers on the batteries.

which way do you wire the?

 

[fromport]

The question I have is depending on weather it is charging or discharging the polarity changes same as the breakers on the batteries.

Polarity (+/-) doesn't change. the flow of the amps through the breakers changes.

which way do you wire the?

Get that information from the manufacturer. They should provide that. And they should know best.

 

[Bud Martin]

Ok rather than starting a new thread I’ll ask here.

I want an breaker on an inverter. I have an expensive big breaker like shown in previous respons. The question I have is depending on weather it is charging or discharging the polarity changes same as the breakers on the batteries.

which way do you wire the?

Are you talking about Inverter that has DC input and convert it to AC or you are talking about All In one unit that has charger and inverter?
If it is just inverter then you can use polarized DC breaker since current only flow on way into the inverter, not like the battery that has current flow both ways (charging and discharging) so it needs to be non-polarized DC breaker.
BTW, if you turn off the power to the inverter and let it sits for long period of time, the capacitor bank in the inverter will be discharged, so when you apply the power to the inverter, you will have high inrush current so you should have a way to pre-charge the capacitor bank first before turning on the breaker.

 

[DPC]

Does it need to be a breaker?

You might find a cheap fused disconnect used on ebay

Fuses are pretty darn hard to beat
The correct choice of fuses are superior to breakers for speed and current limiting in a short circuit

On my previous post I talked about a three phase breaker wired up for dc

Looked like this

The Ontario code had a provision for running ungrounded dc power supplies with a break on both the ac and dc side

You could do the same thing on the third phase break the negative