DC Breaker

[Ben2022]

Ok so I just realized I may be playing with fire nearly literally. I have no breaker between the battery stack and Sol Ark

Here’s pertinent part of my setup:
Sol Ark 15k
1000AH Ruixu batteries - the 10 stack cabinet
10ft of 4/0 welding wire for battery feed

I THOUGHT I didn’t need it since the Sol Ark has a breaker built in and they are server rack batteries with built in breakers.

NOW, I’m questioning it after a few searches on here. I saw a 1.25 rule meaning I’d need a 400 amp breaker…

Can someone provide some clarification? Do I need one? How large for 4/0 welding wire with a 315 amp limit?

 

[BentleyJ]

If each of the 10 individual rack batteries are connected to a bus bar in the cabinet, the battery breaker will provide over current protection as long as the wire from the batt to the bus bar is rated at least as high as the individual breaker.

Don't recall what size the breaker is installed in the Sol-Ark 15K. As long as the breaker and the ampacity of the 4/0 welding cable are equal you don't need any other protection.

That said, If you wanted to be extra cautious a fuse placed on the 4/0 cable at the battery cabinet connection would protect the cables if a short circuit were to occur on the the 4/0 wire somewhere between the battery cabinet but before the Sol-Ark breaker.

 

[Ben2022]

The breaker on the Sol Ark battery connector is 200 amp

All batteries are connected to the cabinet buss bar individually. I BELIEVE it came with 4 AWG they are only like 6” long.

 

[Ben2022]

If each of the 10 individual rack batteries are connected to a bus bar in the cabinet, the battery breaker will provide over current protection as long as the wire from the batt to the bus bar is rated at least as high as the individual breaker.

Don't recall what size the breaker is installed in the Sol-Ark 15K. As long as the breaker and the ampacity of the 4/0 welding cable are equal you don't need any other protection.

That said, If you wanted to be extra cautious a fuse placed on the 4/0 cable at the battery cabinet connection would protect the cables if a short circuit were to occur on the the 4/0 wire somewhere between the battery cabinet but before the Sol-Ark breaker.

The breaker on the Sol Ark battery connector is 200 amp

All batteries are connected to the cabinet buss bar individually. I BELIEVE it came with 4 AWG they are only like 6” long.

 

[BentleyJ]

I looked up the Sol-Ark manual and it shows a 4 pole breaker, all handles tied together with 2 Pos & 2 Neg battery connections. Are you running parallel 4/0 cables between the batt rack and the Sol-Ark or single cables? OR perhaps a single set of 4/0 that is split and then connects to all 4 input terminals. In the later case, this could allow up to 400A before the breaker trips. While ampacity charts can vary somewhat, 400A is allowed at 100% duty cycle on 3/0 welding cable up to 50' length. With 10' of 4/0 your set up should be OK.

That said, if you are only using 2 of the 4 battery input terminals both charging and discharging are limited to 200A thus severely derating the capability of the inverter.

Each rack battery has built in current limiting set at 100A (a few seconds of peak is allowed above this value) 4AWG fine strand cable is sufficient to trip the breaker. With 10 batteries no single set of cables is ever going to be operating at max capacity continuously.

In my opinion the decision to add a fuse on the battery rack end of the 4/0 cable would depend on if the cable is exposed and subject to damage and shorting or if its in some kind of conduit. I think I would opt for putting the battery cable in flex conduit rather than adding a fuse. With 10 rack batteries, there is a possibility of getting a 1000A burst so your concern is legitimate.

 

[Ben2022]

I looked up the Sol-Ark manual and it shows a 4 pole breaker, all handles tied together with 2 Pos & 2 Neg battery connections. Are you running parallel 4/0 cables between the batt rack and the Sol-Ark or single cables? OR perhaps a single set of 4/0 that is split and then connects to all 4 input terminals. In the later case, this could allow up to 400A before the breaker trips. While ampacity charts can vary somewhat, 400A is allowed at 100% duty cycle on 3/0 welding cable up to 50' length. With 10' of 4/0 your set up should be OK.

That said, if you are only using 2 of the 4 battery input terminals both charging and discharging are limited to 200A thus severely derating the capability of the inverter.

Each rack battery has built in current limiting set at 100A (a few seconds of peak is allowed above this value) 4AWG fine strand cable is sufficient to trip the breaker. With 10 batteries no single set of cables is ever going to be operating at max capacity continuously.

In my opinion the decision to add a fuse on the battery rack end of the 4/0 cable would depend on if the cable is exposed and subject to damage and shorting or if its in some kind of conduit. I think I would opt for putting the battery cable in flex conduit rather than adding a fuse. With 10 rack batteries, there is a possibility of getting a 1000A burst so your concern is legitimate.

I’m using a splitter to use both battery lugs. The battery cable isn’t really in any conduit I was told that was against the rules for Ca to have DC cable in conduit inside a building. While I’m not too worried about inspections I am trying to keep it close to what’s required “just in case”. So it sounds like I should be ok with the breaker. Here’s a few pic of the setup. One of these were taken while I was still working on it so it’s not as sloppy now as it looks.

 

[BentleyJ]

I'm not sure why there would be an NEC prohibition to protecting DC battery cables from impact and/or mechanical damage. While there are sections that prohibit putting NM type cable in conduit, that is limited to multi-conductor cable that already has an outer jacket thus heat dissipation becomes an issue.

Now curiosity is begging to look into this further. Perhaps @timselectric or one of the other code experts can help?

 

[robbob2112]

A couple of things or more - was this permitted and inspected? I don't care but can make a difference in answers

• Each battery needs a fuse or breaker between the positive pole and the bus bar. If they have built in breakers that is great. Looking online there is only a small switch per battery with no mention of fuse or breaker. What this means is that if there is a fault in one battery that is a short from a failed BMS the other 9 will dump 100 amps each into the failed pack. This would cause the 4 awg wire to immediately flash to several hundred C in a fraction of a second. 900amps will do that to you. I dunno how the battery would hold up to that but I wouldn't want to find out. If I were you I would immediately purchase 10 class T fuses 125amps each and holders and install them at the bus bar and connect your 4 awg wires to them. They are, 30cm long 4awg included with the rack.
• The connector looks like an Anderson SB350, max current 450amps. Assuming the wire is welding wire in a rubber like sheath it can carry 440amps using the windy nation welding wire charts. So this checks.
• There should be a 500 amp class T JJLN fuse inside the battery cage where the positive wire of the anderson connectors is attached in a fuse block with cover. This is 400amps +20%, nearest size. Without this fuse a short along the battery cables to where they enter the raceway would cause the 1000 amps to melt the sheath to melt the sheath in 5 second and then the real issue happens. The problem is a 400amp breaker would trip in around 5 seconds. But, 2 x 200amp breakers
• That Y connector from the two double lug 200amp connectors is just wrong. It can be done as a bus bar so long as it is at least a quarter inch thick. But my real problem with it is the contact patch. It should be a double lug where the 4/0 cable attaches if you want to fudge it, but in reality it should be the lug I am posting at the end. Seems like someone cut corners.

The NEC rule says that DC lines like this MUST be in metal conduit when in or on a dwelling. The state can add rules to go stricter but not take them out or reduce them. My other major problem is where the NEC states the conductors must be protected from harm. This usually means inside conduit or inside a metal raceway. It doesn't mean a white sock attached to the wall. Inside LFMC, rigid, EMT, or a raceway. The NEC does say the DC wiring can't be in the same conduit or raceway as the AC wiring so that is another problem from the look of it.

Where they might have gotten not in conduit is the rule for dc wire under 50v not being required to be in conduit. Problem is the battery voltage is 51.2v. Older lower voltage systems didn't need it and new stuff does.

If this was installed without a permit I would suspect the installers of falsehoods. And if it was inspected the inspector was not doing his job.

https://www.1sourcedist.com/product/detail/5318098/burndy-corp-ya28l4tcg1

 

[Ben2022]

A couple of things or more - was this permitted and inspected? I don't care but can make a difference in answers

• Each battery needs a fuse or breaker between the positive pole and the bus bar. If they have built in breakers that is great. Looking online there is only a small switch per battery with no mention of fuse or breaker. What this means is that if there is a fault in one battery that is a short from a failed BMS the other 9 will dump 100 amps each into the failed pack. This would cause the 4 awg wire to immediately flash to several hundred C in a fraction of a second. 900amps will do that to you. I dunno how the battery would hold up to that but I wouldn't want to find out. If I were you I would immediately purchase 10 class T fuses 125amps each and holders and install them at the bus bar and connect your 4 awg wires to them. They are, 30cm long 4awg included with the rack.
• The connector looks like an Anderson SB350, max current 450amps. Assuming the wire is welding wire in a rubber like sheath it can carry 440amps using the windy nation welding wire charts. So this checks.
• There should be a 500 amp class T JJLN fuse inside the battery cage where the positive wire of the anderson connectors is attached in a fuse block with cover. This is 400amps +20%, nearest size. Without this fuse a short along the battery cables to where they enter the raceway would cause the 1000 amps to melt the sheath to melt the sheath in 5 second and then the real issue happens. The problem is a 400amp breaker would trip in around 5 seconds. But, 2 x 200amp breakers
• That Y connector from the two double lug 200amp connectors is just wrong. It can be done as a bus bar so long as it is at least a quarter inch thick. But my real problem with it is the contact patch. It should be a double lug where the 4/0 cable attaches if you want to fudge it, but in reality it should be the lug I am posting at the end. Seems like someone cut corners.

The NEC rule says that DC lines like this MUST be in metal conduit when in or on a dwelling. The state can add rules to go stricter but not take them out or reduce them. My other major problem is where the NEC states the conductors must be protected from harm. This usually means inside conduit or inside a metal raceway. It doesn't mean a white sock attached to the wall. Inside LFMC, rigid, EMT, or a raceway. The NEC does say the DC wiring can't be in the same conduit or raceway as the AC wiring so that is another problem from the look of it.

Where they might have gotten not in conduit is the rule for dc wire under 50v not being required to be in conduit. Problem is the battery voltage is 51.2v. Older lower voltage systems didn't need it and new stuff does.

If this was installed without a permit I would suspect the installers of falsehoods. And if it was inspected the inspector was not doing his job.

https://www.1sourcedist.com/product/detail/5318098/burndy-corp-ya28l4tcg1

It’s in an unattached outbuilding and I never had it inspected or permitted but wanted to keep it as close as I could in case the day came I needed to have it permitted. I did all the install soup to nuts. (Only thing I haven’t completed is the external emergency shutdown. Just have to wire the switch)

I talked to one local solar installer that does battery back up and a separate electrician regarding the conduit. Both said not needed. Sparky said it’s a no go for DC in conduit, installer said not needed.

Here is the battery connector I used. I saw it on a few other Sol Ark installs. Its purpose is to allow a higher charging amperage from the Sol-Ark when charging large battery stacks. Sol-Ark limits the charging per lug. Battery Splitter

So you’re saying I should fuse every positive battery connection at the bus bar. I’ll have to see how I can make that work just with physical space in the cabinet.

The only thing running through the “snake skin” are the the battery cables, a ground wire to ground the cabinet and the battery data cable (shielded Cat 6)

If I need a 500 amp fuse between the bus bar main and the Anderson I think there’s room on the back side that I can make that work. Can I use a breaker or should it be a fuse? Any recommendations?

 

[robbob2112]

Fuses react about 10 times faster than breakers. So 5 seconds of 1000amps becomes 50 seconds.

So here is a suggestion on fuses because of the limited space. Put a MRBF holder bolted to the bus bar and then a 125amp fuse on that with the lug on top. The lug needs to be a wide one to sit flat so you might have to clip the current one off and recrimp it. Dell city has reasonable prices on them. You can't trust amazon, there are many fakes. The MRBF has a similar AIC to the class T.

So on the sb350 you can just attach the other end of the positive cable to the of the fuse holder then then a short cable to the bus bar. Or, since this isn't something you will ever want to move loose the SB350. The thing about anderson connectors is you need to unplug and plug once a year or so or over time they will rise in resistance. At 400amps any resistance is a lot of heat. Were it me I would drop it.

I would put 6x6 raceway or so around the wall to put the dc cables in. Don't leave a bunch of extra slack.

Interesting on the bus bar adapter, that must be a local creation from that website. Not sure what I think about it.


Read before and see what you think...

For the 10 battery stack, go to the thread in my signature and there is a link about parallel battery connections. He didn't extend the math to 10 batteries, but what he did makes me think it might be worth cutting the bus bar in your cabinet in half and connecting 4 cables from the right spots to a set of short 3 lug bus bars and the middle lugs of those to you inverter on neg and 500amp fuse on the positive then the inverter. all of this to keep the batteries in balance.



The install looks very clean with only a few thing I noted so good job on that score.

 

[ksmithaz1]

If you put the cable in raceway you have to beef it up or run multiple connectors to get 400A. It also makes your battery rack immobile. You have dual 200A breakers, thus 400A of feed capacity with the given setup. Kind of up to you, but I'd probably run two cables and fuse them with 200-250A fuses.

 

[robbob2112]

If you put the cable in raceway you have to beef it up or run multiple connectors to get 400A. It also makes your battery rack immobile. You have dual 200A breakers, thus 400A of feed capacity with the given setup. Kind of up to you, but I'd probably run two cables and fuse them with 200-250A fuses.

Nobody is moving a rack full of batteries.... and from what I can see he is avoiding covering the outlet and also allowing the NEC required 36in in front of the breaker panel.

The other thing, the NEC only requires derating the wire capacity if there are more than 2 current carrying wires in the raceway. So a 6x6 or smaller, all the way to 2x2 would work. Personally I would use 2x4 raceway since it is flatter to the wall and cheaper.

The NEC says the cross section area max fill in the raceway is 20%. The wire is 1in square so right at 2x2 so I would go one size up and use 2x4. And you can always open it to inspect the wire with a thermal camera.

 

[ksmithaz1]

Nobody is moving a rack full of batteries.... and from what I can see he is avoiding covering the outlet and also allowing the NEC required 36in in front of the breaker panel.

I rolled mine over about 3 feet this morning, doing some work.

The other thing, the NEC only requires derating the wire capacity if there are more than 2 current carrying wires in the raceway. So a 6x6 or smaller, all the way to 2x2 would work. Personally I would use 2x4 raceway since it is flatter to the wall and cheaper.

So we want to tote 400A right?

4/0 copper is rated at 195-230-260A 60-75-90C In a raceway or conduit with not more than three current carrying conductors

4/0 copper is rated at 300-360-405A 60-75-90C in free air ambient 86F.

Thus I conclude you are going to need to double up the 4/0 if you stuff it in something. You have to go all the way to 500 to get 400A in a raceway on a single conductor. Feel free to enlighten, perhaps I am mis-reading.

The NEC says the cross section area max fill in the raceway is 20%. The wire is 1in square so right at 2x2 so I would go one size up and use 2x4. And you can always open it to inspect the wire with a thermal camera.

Not even talking about fill. Free to air allows for something like a foot entering a termination point. Start stuffing it in a tray with a bunch of other stuff and it's going to drop even further.

 

[Ben2022]

Nobody is moving a rack full of batteries.... and from what I can see he is avoiding covering the outlet and also allowing the NEC required 36in in front of the breaker panel.

The other thing, the NEC only requires derating the wire capacity if there are more than 2 current carrying wires in the raceway. So a 6x6 or smaller, all the way to 2x2 would work. Personally I would use 2x4 raceway since it is flatter to the wall and cheaper.

The NEC says the cross section area max fill in the raceway is 20%. The wire is 1in square so right at 2x2 so I would go one size up and use 2x4. And you can always open it to inspect the wire with a thermal camera.

Yes I was trying to be mindful of the 36” rule with the panel.

I do plan on moving my batteries around to epoxy the floor when the time comes. That’s why I used the Anderson connector.

Is this the type of Raceway you are thinking of?

 

[robbob2112]

Exactly right - protect the wire and allow the heat out. Are you using fine stranded 105c welding wire for these two?

The windy nation chart shows 440amp capacity. This can vary a bit from vendor to vendor - the generic NEC chart is for course stranded THHN or equivalent. But it also says to use whatever the wire MFG rates the wire as.

Once thing doubling up does for you is allow a higher draw impulse. Meaning if the inverter goes from 100amps to 400amp suddenly the extra wire allows it through verse the existing wire acting as a choke point.

I doubt tht is a problem

 

[Ben2022]

Exactly right - protect the wire and allow the heat out. Are you using fine stranded 105c welding wire for these two?

The windy nation chart shows 440amp capacity. This can vary a bit from vendor to vendor - the generic NEC chart is for course stranded THHN or equivalent. But it also says to use whatever the wire MFG rates the wire as.

Once thing doubling up does for you is allow a higher draw impulse. Meaning if the inverter goes from 100amps to 400amp suddenly the extra wire allows it through verse the existing wire acting as a choke point.

I doubt tht is a problem

Yes it’s very fine high strand welding wire. Got it from a local electrical supply house so not eBay or Amazon stuff. I did not look up the specific brand just a generic amp chart for high strand welding wire when making sure I was good. I was shooting for 250 amp wire with a margin of error and the physical flexibility to run it where needed.

I’ll look into getting that raceway if that will work. Any problem with me leaving the snake skin on? What about leaving the ground and data wire in place in the raceway?

 

[robbob2112]

what is the thermal rating off the wire? it comes in 90c and 105c and higher.

I would remove the snake skin to allow airflow around it.
And for the data cable I would attach it to the bottom or just lay it on top but not in the raceway. The ground wire is a non-conducting wire and can go in the raceway.

 

[Ben2022]

what is the thermal rating off the wire? it comes in 90c and 105c and higher.

I would remove the snake skin to allow airflow around it.
And for the data cable I would attach it to the bottom or just lay it on top but not in the raceway. The ground wire is a non-conducting wire and can go in the raceway.

Just looked - the casing says 105c

 

[robbob2112]

So that means it is able to handle a touch over 400amps. If you ever get close to maxing out your current draw I would double up. Then they are good to 800amps and everyone is happy with it in the raceway.

AND wait, I read the specs your vented raceway is plastic verse metal - so no joy with it - here is some 6x6 metal that would do the job, just order sections - there is plenty of room for 2 wire runs and air and while you would derate the wire some 2 runs (4 wires) of 4/0 in there wouldn't even warm it up.

type-1-gutter-trough-cgt-seriesCGT1244

type-1-gutter-trough-cgt-seriesCGT1244CGT1244

enclosurehub.com

I assume you used the included torid coil around the DC wires when doing the Sol-Ark?

 

[Ben2022]

So that means it is able to handle a touch over 400amps. If you ever get close to maxing out your current draw I would double up. Then they are good to 800amps and everyone is happy with it in the raceway.

AND wait, I read the specs your vented raceway is plastic verse metal - so no joy with it - here is some 6x6 metal that would do the job, just order sections - there is plenty of room for 2 wire runs and air and while you would derate the wire some 2 runs (4 wires) of 4/0 in there wouldn't even warm it up.

type-1-gutter-trough-cgt-seriesCGT1244

type-1-gutter-trough-cgt-seriesCGT1244CGT1244

enclosurehub.com

I assume you used the included torid coil around the DC wires when doing the Sol-Ark?

I don’t know that I would ever even get close to drawing 200 amps I just want to NOT have a fire.

Bummer on the race way I was hoping for someone easy to work with and less intrusive looking.

Yes the torids are on the DC line plus I’ve added a ton on others. Each solar panel has one AT the panel, solar strings have one per string, dc lines also have one close to the battery too (opposite the Sol Ark). I just don’t have any high saturation ones to put on the AC lines. The ones I saw were $$ especially if I need 6 (3 in 3 out)

 

[robbob2112]

The problem is you really have no way to limit it other than the fuses. If the inverter shorts it will pull as much current as the batteries will deliver. You could put a class T at the inverter end of the long cables and be sure if there is a short anywhere along the line they are safe. That much current in under a second is a worry