What brand high amperage circuit breakers people use in Europe (400A 60V required)

I've been looking for a suitable DC circuit breaker for 400A 60V (for my 48 16S 280AH LFP battery) and I'm having a hard time finding a suitable one at a reasonable price in Europe (Poland, but the market for electrical parts is very similar in most of the EU). What is reasonable for me regarding a price? About $100 I'd say is fine. I can live with maybe 50% more, but asking $500+ for a circuit breaker is taking the piss.

I've asked the inverter seller (Easun SMH-ii-7k) if the negative battery terminal can be grounded. If so, I can just use a single pole breaker rather than 2.

There are these relatively inexpensive circuit breakers from Nanque Electric Store on Aliexpress, but it doesn't insipre confidence a 400A rated unit can only be fitted with 70mm2 wire (AWG 1) tops as I'm using 120mm2 (AWG 0/4) for all my battery connections.

So what do people in Europe buy for a circuit breaker? Or maybe it makes some sense to import from other parts of the world? In such case, what circuit breakers for 400A do people in the US, or elsewhere use? I read bussman makes good breakers in the US, but I haven't managed to find a 400A unit.

How did I decide I need 400A and not, lets say 200A for a 7kW inverter? My BMS is rated for continous 200A, 350A peak so it makes sense to have a breaker of last resort at 400A. Also, it seems a rule to size the breaker for twice the max expected continous load. Therefore 400A. If I've got it wrong, please let me know.

I can switch the battery off and on using the bluetooth app, and the fuse would probably meet the local electric code requirements. But I'd feel much better having a circuit breaker that can be reset instead.

I like the Midnite 125V 250A DC breakers, currently pretty cheap here, you could double up on them for 500A. Also they are on a time delay curve so even one should be good for over 300A for a temp surge situation.

Oh and the breaker/fuse sizing is to protect the wire. You want the breaker to trip before the insulation catches on fire.

Luk88 said:

How did I decide I need 400A and not, lets say 200A for a 7kW inverter? My BMS is rated for continous 200A, 350A peak so it makes sense to have a breaker of last resort at 400A.

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I disagree.

First you must see what is the max charge/discharge current of your inverter.

Then size the fuse/breaker to be approx. 20% higher than that.

Then size your DC cables to handle 20% greater than the fuse/breaker.

At the end of the day, you need to supply enough current to your inverter and you need your fuse / breaker to be suitably sized to protect the DC cables.

You could look at something like the Jean-Muller KETO-00 Fuse-Switch-Disconnector range, which is readily available in the UK and Europe.

Brucey said:

I like the Midnite 125V 250A DC breakers, currently pretty cheap here, you could double up on them for 500A. Also they are on a time delay curve so even one should be good for over 300A for a temp surge situation.

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I'm not sure putting circuit breakers in parallel is a great idea (or code compliant).

250A is definitely not enough... (inverter is rated at almost 300A for up to 5s and the BMS at 350A surge)

SeaGal said:

I disagree.

First you must see what is the max charge/discharge current of your inverter.

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Max discharge current of the inverter is 300A briefly (5s)

SeaGal said:

Then size the fuse/breaker to be approx. 20% higher than that.

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I have the BMS overcurrent protection for that. Sized at 350A

SeaGal said:

Then size your DC cables to handle 20% greater than the fuse/breaker.

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So my cables (120mm2, awg 0/3 not 0/4 as I written before) can handle 340A when spaced and unenclosed, so easily 20% more than the peak inverter load and bms cutoff.

SeaGal said:

At the end of the day, you need to supply enough current to your inverter and you need your fuse / breaker to be suitably sized to protect the DC cables.

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400A seems perfect for this purpose based on the above. Based on some DC welding experience it will take a lot more than 400A for few seconds to set that cable on fire. I've used 70mm2 for welding with 350A. It gets barely warm.

What would you choose in my place? (with these numbers).

SeaGal said:

You could look at something like the Jean-Muller KETO-00 Fuse-Switch-Disconnector range, which is readily available in the UK and Europe.

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Sadly, KETO-00 is up to 160A, they don't have 400A. They do have 160A,250A and then 630A (at 690V). I looked up the prices... These large breakers are twice the price the previous ones I called expensive ($750+).

So the search continues.

I'm by no means an expert, but Noark make good DC breakers not sure about a 2 pole of that size. but this one will suit but with an extra pole
Noark N852724-3P-MCCB 400A/750VDC my guess would be that these are expensive.
You could go for Mersen NH Fuse disconnector not a breaker but you can get fuses up to 630A Voltaconsolar sell them in the UK
Hope this helps

MattiFin said:

Fuse switch disconnector KETO-2-3/F/HT 400A T200113002

onninen.pl

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Thanks. I couldn't find it on the their website.

However, I'm not seeing any DC rating and it isn't actually a circuit breaker. It is a fuse holder so you have to equip it with fuses (single use if they trip). It is unclear if it can be used to "break the circuit" at will by pulling a handle like a typical circuit breaker would.

Somethingobscure said:

I'm by no means an expert, but Noark make good DC breakers not sure about a 2 pole of that size. but this one will suit but with an extra pole
Noark N852724-3P-MCCB 400A/750VDC my guess would be that these are expensive.
You could go for Mersen NH Fuse disconnector not a breaker but you can get fuses up to 630A Voltaconsolar sell them in the UK
Hope this helps

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Thanks. I have to do more research if these are available in 2 or 1 pole configuration.

BTW, for now I just got a couple fuses and a cheap holder, but I do intend to fit a proper breaker eventually. For anyone unfamiliar see how comically large a 400A 500V fuse and its holder it. Yes, that's a 280ah lifepo cell to scale

Ok so say your BMS can surge to 350A. What is the load going to be doing? It seems unlikely that a high frequency inverter like this will ever approach that level. The mnedc250 breaker has a trip point of 313A in the model I have with a delay value of 16.

400a is absolutely nuts for this inverter..
200a at 51,2 nominal voltage is 10240 watts..
Your inverter will be overloaded long before that

For my sunsynk 12k's I use a 250a tomzn..
Have tested that it does what it should do , and it is huge , heavy and spring loaded bidirectional

Connected with 95mm2 cable



I think this is a similar one

In Europe ABB is probably your best option for brand name high amperage DC circuit breakers.

But I would use fuses and disconnects. DC and circuit breakers get along like two cats in a bag.

hwy17 said:

In Europe ABB is probably your best option for brand name high amperage DC circuit breakers.

But I would use fuses and disconnects. DC and circuit breakers get along like two cats in a bag.

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Looked at Abb...

For a slightly comparable mccb to the tomzn , I would need to spend over 300 euro, the noark's are even more expensive here

Luk88 said:

Thanks. I couldn't find it on the their website.

However, I'm not seeing any DC rating and it isn't actually a circuit breaker. It is a fuse holder so you have to equip it with fuses (single use if they trip). It is unclear if it can be used to "break the circuit" at will by pulling a handle like a typical circuit breaker would.

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For sure it is NOT rated for DC break at 400A. You better yank the handle really swiftly if you ever want to use it for breaking the circuit at DC.

houseofancients said:

400a is absolutely nuts for this inverter..
200a at 51,2 nominal voltage is 10240 watts..
Your inverter will be overloaded long before that

For my sunsynk 12k's I use a 250a tomzn..
Have tested that it does what it should do , and it is huge , heavy and spring loaded bidirectional

Connected with 95mm2 cable



I think this is a similar one

https://a.aliexpress.com/_EQKwUYB

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I've said it before. The circuit breaker is not to protect my inverter. I have the BMS overload cutoff for that.

The circuit breaker has two functions. It is a last resort "holy shit there is a spanner shorting the battery distribution bus" protection and "the battery is on fire isolate it quick and run the f*** outta here".

For some people (and one can reasonably argue it is why this type of circuit breakers and fuses were invented) is to protect the wiring. Not the appliances, not the power source. It is to prevent the house burning down and wires melting in the walls.

So don't say it is too much, because "the inverter will never pull this power" It is rated at 2x power for up to 5s so in theory it could pull 14kW (as it is rated at 7kW continuous) which just above its default low voltage cutoff of 42V is 333A. 333A * 1.2 = 400A.

Luk88 said:

I've said it before. The circuit breaker is not to protect my inverter. I have the BMS overload cutoff for that.

The circuit breaker has two functions. It is a last resort "holy shit there is a spanner shorting the battery distribution bus" protection and "the battery is on fire isolate it quick and run the f*** outta here".

For some people (and one can reasonably argue it is why this type of circuit breakers and fuses were invented) is to protect the wiring. Not the appliances, not the power source. It is to prevent the house burning down and wires melting in the walls.

So don't say it is too much, because "the inverter will never pull this power" It is rated at 2x power for up to 5s so in theory it could pull 14kW (as it is rated at 7kW continuous) which just above its default low voltage cutoff of 42V is 333A. 333A * 1.2 = 400A.

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If this is your reasoning, use a 400a t-class fuse ( like you already should be using )

Luk88 said:

I've said it before. The circuit breaker is not to protect my inverter. I have the BMS overload cutoff for that.

The circuit breaker has two functions. It is a last resort "holy shit there is a spanner shorting the battery distribution bus" protection and "the battery is on fire isolate it quick and run the f*** outta here".

For some people (and one can reasonably argue it is why this type of circuit breakers and fuses were invented) is to protect the wiring. Not the appliances, not the power source. It is to prevent the house burning down and wires melting in the walls.

So don't say it is too much, because "the inverter will never pull this power" It is rated at 2x power for up to 5s so in theory it could pull 14kW (as it is rated at 7kW continuous) which just above its default low voltage cutoff of 42V is 333A. 333A * 1.2 = 400A.

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Most common gG NH fuse will handle about 4x nominal current for 10 seconds before blowing. Or abouts 5x nominal for 5 seconds. Not infinite number of overload cycles or when already loaded for maximum for hours(hot)

200A fuse should be plenty for 7kW inverter as it can handle 5s peaks up to 42kW

MattiFin said:

Most common gG NH fuse will handle about 4x nominal current for 10 seconds before blowing. Or abouts 5x nominal for 5 seconds. Not infinite number of overload cycles or when already loaded for maximum for hours(hot)

200A fuse should be plenty for 7kW inverter as it can handle 5s peaks up to 42kW

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Hmm, OK, I haven't considered that.

Still putting a circuit breaker smaller than 1C on a battery seems oddly limiting. IDK, perhaps I am wrong in this. I'll have to find more resources on this topic.

Please consider all the sensible advice given above.

With batteries at 53-54V, 400A represents 16kW. I find it hard to believe you will get that much out of a 7kW inverter, for however short time period. If I am wrong, then make sure that the AC side of your wiring is designed to handle 16kW as well.

Whatever your experience of welding equipment I would not recommend using a 400A fuse/breaker for wire which is rated at 340A.

Luk88 said:

Still putting a circuit breaker smaller than 1C on a battery seems oddly limiting.

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You are not comparing like with like. The limit will be the inverter's current draw, not the battery's capacity.

For example, my Solis can draw only 100A maximum. I have 280Ah of battery storage, so that is under 0.4C. If I were to double my battery capacity, I would only be drawing under 0.2C.

SeaGal said:

Please consider all the sensible advice given above.

With batteries at 53-54V, 400A represents 16kW. I find it hard to believe you will get that much out of a 7kW inverter, for however short time period. If I am wrong, then make sure that the AC side of your wiring is designed to handle 16kW as well.

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Yes, I'm making sure of it. That is quite easy as tables for recommended conductors in house wiring and ground cables are available for free online.

SeaGal said:

Whatever your experience of welding equipment I would not recommend using a 400A fuse/breaker for wire which is rated at 340A.

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But this cable is not rated at 340A.

Boring standards bit italicised and shrunk for easy skipping.

You're probably quoting a value from a standard like VDE 0298-4 06/13 table 11 which has 344A for 120mm2. But I'm using a HO1N2-D 120mm2 EN50525-2-81 cable (its actually designed for Arc welding, which means it has thinner strands, and is more flexible which I need). The manufacturer datasheet specifies its current rating should be as per VDE 0298 Part 4, table 16 (not 11). Trying to find the complete table 16 is not easy. One is supposed to pay 110Eur for the priviledge so I can't read the value directly. But consider the 50mm2 cable. Normal cable of this size in table 11 is rated at 198A (this includes PVC, rubber and flame retardant cables), the same arc welding cable (at 100% duty cycle, mounted on a wall spaced from other cables by a specified amount) is rated at 274A. 38% more. Then lets take 25mm2 - this in table 11 is rated at 129A, in table 16 it is at 173A this time 34% more. I don't know why they rate these flexible cables at 3X% more than normal cables. Before any one says: because you only weld for few minutes, let me say the table specifies the duty cycle and for lower than 100% the ratings are much higher.

So it is reasonable to assume a 120mm2 cable in table 16 will be at least rated at 30%+ of table 11 rating which is calculated as 447A continous. It is not going to burst into flames at 400A

In fact we can calculate how much heating power will be generated. The cable is 4m long (per leg). This comes to 1.1mOhm. At 400A this will cause a voltage drop of 0.44V. This times 400A is 176W of heating power spread over 8m of wire touching a concrete basement wall that is usually at about 5C.

SeaGal said:

You are not comparing like with like. The limit will be the inverter's current draw, not the battery's capacity.

For example, my Solis can draw only 100A maximum. I have 280Ah of battery storage, so that is under 0.4C. If I were to double my battery capacity, I would only be drawing under 0.2C.

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I've already mentioned the low voltage cutoff is at 41V, so lets take battery's internal resistance into account and say it is 0,2mOhm per cell * 16 is 3.2mOhm per battery which means a voltage drop of 1.2V, we've already calculated the cable will add 0.44 to this. Lets be conservative and say 2V. So the minimum voltage can be 43V and if the inverter tries to push 14kW out it will try to pull 325A. If I expected 100A of load I would put a 70mm2 cable, a 200A fuse and set the BMS to cut off at 150A.

The only thing that has me worried is that these DC breakers have a signiffcant delay as was mentioned by a previous poster which would mean if the inverter shorted and the BMS failed short at the same time(rather unlikely, but who knows) there could be 400A+ going through the inverter for few seconds before the DC circuit breaker reacts. This is not good. A fast acting fuse is much better in this regard.

Luk88 said:

Yes, I'm making sure of it. That is quite easy as tables for recommended conductors in house wiring and ground cables are available for free online.

But this cable is not rated at 340A.

Boring standards bit italicised and shrunk for easy skipping.

You're probably quoting a value from a standard like VDE 0298-4 06/13 table 11 which has 344A for 120mm2. But I'm using a HO1N2-D 120mm2 EN50525-2-81 cable (its actually designed for Arc welding, which means it has thinner strands, and is more flexible which I need). The manufacturer datasheet specifies its current rating should be as per VDE 0298 Part 4, table 16 (not 11). Trying to find the complete table 16 is not easy. One is supposed to pay 110Eur for the priviledge so I can't read the value directly. But consider the 50mm2 cable. Normal cable of this size in table 11 is rated at 198A (this includes PVC, rubber and flame retardant cables), the same arc welding cable (at 100% duty cycle, mounted on a wall spaced from other cables by a specified amount) is rated at 274A. 38% more. Then lets take 25mm2 - this in table 11 is rated at 129A, in table 16 it is at 173A this time 34% more. I don't know why they rate these flexible cables at 3X% more than normal cables. Before any one says: because you only weld for few minutes, let me say the table specifies the duty cycle and for lower than 100% the ratings are much higher.

So it is reasonable to assume a 120mm2 cable in table 16 will be at least rated at 30%+ of table 11 rating which is calculated as 447A continous. It is not going to burst into flames at 400A

In fact we can calculate how much heating power will be generated. The cable is 4m long (per leg). This comes to 1.1mOhm. At 400A this will cause a voltage drop of 0.44V. This times 400A is 176W of heating power spread over 8m of wire touching a concrete basement wall that is usually at about 5C.


I've already mentioned the low voltage cutoff is at 41V, so lets take battery's internal resistance into account and say it is 0,2mOhm per cell * 16 is 3.2mOhm per battery which means a voltage drop of 1.2V, we've already calculated the cable will add 0.44 to this. Lets be conservative and say 2V. So the minimum voltage can be 43V and if the inverter tries to push 14kW out it will try to pull 325A. If I expected 100A of load I would put a 70mm2 cable, a 200A fuse and set the BMS to cut off at 150A.

The only thing that has me worried is that these DC breakers have a signiffcant delay as was mentioned by a previous poster which would mean if the inverter shorted and the BMS failed short at the same time(rather unlikely, but who knows) there could be 400A+ going through the inverter for few seconds before the DC circuit breaker reacts. This is not good. A fast acting fuse is much better in this regard.

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If the inverter is allegedly pulling 325A, what's the big deal if it can pull 400A?

I don't believe this can power 14k for 5 seconds, but I guess final user test will be the truth. There are inverters that can surge double their rated capacity as long as the battery system can keep up, but they cost more (Victron, Schneider, Midnite etc).