Battery disconnects / isolators @ 400A

I appreciate it, but I’m in no hurry for answers, so don’t worry about me yet :slight_smile:

I might take you up on that once the tools come out.

Right. The Pylontechs don’t have externally accessible breakers though, so that’s the right thing to do in your case I think.

I’m definitely not trying to burn my house down, but in this case everything already has a fuse or magnetic breaker. I just need a teeny-tiny 400A isolator…

Following that will then not comply with Sa regulations. All of my parallel as well as three phase installations have separate negatives.

As I read them, the regs require the battery to be isolated positive and negative. The inverters require an unbroken negative connection to each other, not the battery, so the link must be after the battery isolator to both comply and keep the smoke inside if the isolator opens.

So this only really matters if the inverters are simultaneously disconnected from each other AND connected to the grid / generator, but that is very possible in a fuse-blown scenario.

thats why i used busbars which keeps neg connected, after that batteries and mppts have complete disconnectors

Bit then you are not Sans compliant to my knowledge…

SANS doesn’t say each individual piece of equipment must be fully isolatable, only the batteries. (And the MPPT at the PV side, but that’s a different topic really.)

Isolating parallel or three-phase Victrons like that will blow the Ve.Bus if those negative fuses go.

Sorry to be the bearer of bad news :frowning:

(From p35)

The language used here is quite mild, but all videos I’ve seen or in-person conversations I’ve had were a lot harsher about the consequences.

(I’m on an edit storm again…)

@Whatyamacallit Did a 4th version of that picture, like the middle one, but with an additional positive break with a fuse at the battery, like the 3rd picture, which both satisfies SANS, and helps the whole house-burning-down problem.

I think you misunderstand the way I wire my stuff, I comes to the same as the third diagram in your picture. If I pull the fuse everything opens together. I can not open one of the fuses or links separately. One motion kills all.

That point of isolation is also a safety feature… A point the the client can pull open in the case of a extreme emergency. If you plan running your combined units through a single fuse, rather consider a moulded case breaker… I don’t want to pull that fuse under load, or maybe I will with a 2 meter link stick…

I checked sans and install is good.

You only need your sources of power to have both pos and neg disconnected. Once batteries and mppts disconnected from busbar it is totally isolated. I then have the positive from busbar to inverter fused as per victron diagrams the negative stays solidly connected to bus bar especially in parallel inverter systems.

1 Like

Are the inverter negatives disconnect at this point?

If so, you have a problem if the grid can still be on, since the inverters will still be powered and connected to each other via the Ve.Bus, which burns out due to the current.

If after pulling the fuses (all together), the inverter negatives are still connected to each other, you’re fine.

It sounds like you built a busbar around the Ketos with links?

Haha yes I have both 2 and 3 combined, it’s called the super safe system, backup of a backup fused failsafe

Wait I must run trough a couple of installs, residential connected to grid, negatives bonded on inverter side of things. Fuse disconnects from battery with negatives still connected.

2 installations, fairly big 3 phase and paralleled, negatives bonds through separate fuses, but off grid… Fuses disconnects, no negative bonding.

I am still interest interested in learning more about what currents can damage the inverter in this case… I use to try and blow blue equipment, not easy, maybe now you gave me a new test…

1 Like

So in this case, you still might burn the comms out if a single inverter negative fuse blows and the rest are still running. They’re supposed to shut down in that case, but unsure how quickly.

In 2010 we built a “2/3-phase” system using 2x Quattros as a UPS. (Why? Because existing supply wiring.) Learnt a lot then. These things don’t break easily, which is why I’m super-paranoid when they tell you to avoid a scenario.

Very quick, of that I am certain.

In my case that could be the battery breaker, then the isolator.

But this looks quite pretty :slight_smile:

Not sure if I want to bet the house (literally) on ACDC…

I can supply dc moulded case breakers at quite a good price.

It is just an isolator, so it is not meant to break a load or fault current.
This is what I would use in the combined negative leg:
They fit an NH2 fuse holder (400A) size and even bigger NH’s if you want.
This clip was from the Mersen site, but there are many manufacturers.


OK, that was kind-of what I was looking for. Coupled with a JM/Mersen disconnect.

Would only be for maintenance.

I pull this back, the prices went up 6 fold since I last bought 2 months back… I am stunned, awaiting some kind of explication from suppliers. Very sorry for waisting your time and giving you some kind of hope.