6000XP Breakers. Explanation needed...

[Onehand]

Can someone explain to a stupid old man how these breakers do anything other than cut AC/DC power(s) to the inverter in the event of an catastrophic event within the inverter, as well as serving as disconnects?

I understand how they would trip if there were shorts on the feed lines but what about the big battery cables, the 2 - 2/0's to buss bars and the 4/0's to the server rack buss bars? What protects those cables?

I just dont see how those XP breakers negate the need for PV disconnects before the inverter and Class T fuses on the battery lines. What am I not seeing here???

 

[timselectric]

Every conductor needs OCP (Over Current Protection). Whether it be a fuse or breaker. To protect the conductor from being overloaded.
This Protection should be placed as close to the source feeding the conductor.
PV conductors are a little different. Because the current is self limiting. (By the panels)
OCP is only required when the available current could exceed the equipment or conductors rating.

 

[Onehand]

Every conductor needs OCP (Over Current Protection). Whether it be a fuse or breaker. To protect the conductor from being overloaded.
This Protection should be placed as close to the source feeding the conductor.
PV conductors are a little different. Because the current is self limiting. (By the panels)
OCP is only required when the available current could exceed the equipment or conductors rating.

Thank You Sir.

That is what I thought. I just see allot of people connecting battery conductors these XP's with no OCP devices.

As far as PV lines go, if a string is putting out 10 amps, that is all it will ever put out unless it suffers a lightning strike or something. I cant see breakers serving any purpose there.

 

[timselectric]

That is what I thought. I just see allot of people connecting battery conductors these XP's with no OCP devices.

They shouldn't be.

 

[Quattrohead]

I think you will find that most of these batteries have over current protection built in either via built in circuit breakers or at least BMS cut off.

 

[Partimewages]

I would never consider a BMS as over current protection. Just to many cheap batteries that I would not trust.

 

[Onehand]

I think you will find that most of these batteries have over current protection built in either via built in circuit breakers or at least BMS cut off.

Is true, both. on the Lifepower4 batteries. 600amps, 1500 short circuit, I would hope all 6 breakers would trip. I imagine a T class fuse around 300 Amps in the main 4/0 line would be faster.

 

[timselectric]

I would never consider a BMS as over current protection. Just to many cheap batteries that I would not trust.

Agree
The BMS is a last resort protection for the battery.
Not for the conductors.

 

[AZ Solar Junkie]

They shouldn't be.

How is the breaker on the battery input on the 6000xp not considered OCP?

 

[Partimewages]

Needs to be at the start of the conductor not the end.

 

[AZ Solar Junkie]

Needs to be at the start of the conductor not the end.

How is one end the start and the other the end? The current flows either direction depending if the batteries are currently charging or discharging…

 

[Quattrohead]

How is one end the start and the other the end? The current flows either direction depending if the batteries are currently charging or discharging…

This is definitely a chicken or egg question haha

 

[ksmithaz1]

How is the breaker on the battery input on the 6000xp not considered OCP?

Technically it is if it stands alone and matches the conductors. It's more of a trust and scale issue. Suppose You have a 300A breaker in the inverter for the battery connection, but you only run 2AWG to your 100A battery. Current flow is bi-directional and we need to make sure no more than 100A flows over the conductor. So you put a 100A breaker/fuse up by the inverter. I have a rack of 6 batteries and a 1/0 connection to a small inverter probably want a 150-200A breaker in line to protect the cable. Batteries could dump 600A on the cable without tripping their individual breakers after all...

Just a little added protection and convenience along with scalability. Coupled with visual sanity. That breaker on a battery cabinet could be in circuit so as not to protect the output lugs.

 

[JAS]

How is one end the start and the other the end? The current flows either direction depending if the batteries are currently charging or discharging…

Curious as well... I thought a great advantage to the 6000XP was not having to add additional breakers/fuses inline of all the connections?

 

[ksmithaz1]

Curious as well... I thought a great advantage to the 6000XP was not having to add additional breakers/fuses inline of all the connections?

No bus, One(1) battery sized with cabling appropriate for the highest rated breaker/fuse = no problem, but does not scale.

 

[AZ Solar Junkie]

No bus, One(1) battery sized with cabling appropriate for the highest rated breaker/fuse = no problem, but does not scale.

Even with a bus and multiple batteries, if the cabling and bus bars are sized appropriately, the 200 amp breaker internal to the 6000xp seems like it is all the protection you need. Adding an additional breaker is just adding another breaker in series with the existing one, which seems unnecessary to me. If the battery cables are not sized to support 200 amps, then yeah I can see the need to connect another (smaller) breaker that is appropriate to protect the smaller cables. One of the selling points of the 6000xp is the lack of the need for additional breakers - at least for the battery and AC connections.

The PV inputs of course don't have breakers, just the disconnect, and the manual does recommend adding DC breakers for the PV inputs.

 

[timselectric]

How is the breaker on the battery input on the 6000xp not considered OCP?

It will provide OCP. (If it's the only thing on the circuit)
It will not provide short protection.
This can only be done at the source. (The Battery)

 

[timselectric]

How is one end the start and the other the end? The current flows either direction depending if the batteries are currently charging or discharging…

The battery is the largest source of current.
The charger is self limiting.
But to completely cover a bidirectional circuit. You must protect it from both ends.
That's what I am doing. I have a breaker at each battery. And a breaker at each AIO.

 

[hwy17]

You don't have to use DC breakers. You can do it all with Fuses, Contactors, and Disconnects and that's how the EV guys do it.

 

[timselectric]

Clarification
The purpose of a breaker or fuse is to protect the conductors.
The built-in breakers only eliminate one side of the equation.