Ground fault to DC (negative) on the new MultiPlus II 15000/48

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pwacquiez asked May 22, '24

Ground fault to DC (negative) on the new MultiPlus II 15000/48

Hello everyone,

It has been 2 years since my single-phase installation on an isolated site worked well with an MP2 48/10000, two MPPT250/100, CERBO...

I bought the MP2 15000 to get more single phase power (and in the hope that the latest model would be a bit quieter). I received it yesterday and installed it. When I wanted to restart my installation, the earth guardian on the direct current side (DOLD IL 5881) immediately indicated an earth fault on the negative.

Indeed, when I disconnect the earth cable from the Multiplus 15000, the tester indicates:

- 48v between the + and the mass of the MP2

- 0 v between - and MP2 ground

Otherwise, the MP2 15000 works, but it is of course too dangerous to use it as is.

What do you think ?

Multiplus-II feature request fault

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MultiPlus-II Product page

MultiPlus-II Manual

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MultiPlus-II 230V Datasheet

VE.Bus Error codes

Faults with Victron equipment are best discussed directly with your dealer - this can be formalised with this support request form.

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Answer 1 · 2024-05-22T09:21:30Z

Duivert NL answered · May 22 at 09:21 AM

sorry off topic:

but your AC connections on the multi are badly crimped and have dangerously open copper connections

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Answer 2 · 2024-05-22T21:53:10Z

pwacquiez answered · May 22 at 09:53 PM

I suppose that the fault comes from a tin solder which makes contact between the negative and the ground or a screw passed through a negative cable inside. but it is guaranteed so I am not going to open it. it’s tedious to take it back to the supplier (~75kg), put the new one back, rewire it…

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Answer 3 · 2024-05-23T13:14:22Z

sharpener answered · May 23 at 01:14 PM

Here is a list of what to test before sending a unit back. Although intended for distributors it might contain some clues.

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Answer 4 · 2024-05-23T20:27:46Z

pwacquiez answered · May 23 at 08:27 PM

I found the problem.

There is a metal bracket behind the negative battery connection. it is in contact with one of the tin points on the electronic card.

I took a picture of the problem with a mirror and added a red arrow.

I slipped a piece of plastic to insulate it.

I don't understand why Victron did not insulate this metal support which is on ground.

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img-3804.jpeg (4.2 MiB)

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Duivert NL commented · May 24 at 04:50 AM

Hi i suggest you send your conclusion and pictures to victron, thats clearly a fabrication error, could be al faulty fabricated batch of multiplus 2 15k’s

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Justin Cook ♦♦ commented · May 23 at 08:35 PM

Unrelated, but please note that neither the Blue Sea battery switch nor any of those surface-mount breakers in your install are suitable for a 48vNom system.

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pwacquiez Justin Cook ♦♦ commented · May 23 at 08:44 PM

Where is the problem please ?

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img-3807.png (505.6 KiB)

Justin Cook ♦♦ pwacquiez commented · May 23 at 08:49 PM

48v maximum, for use on up to 36vNom systems. Your system is running between 54 and 60v, and neither the switch nor the breakers are suitable for that voltage.

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pwacquiez Justin Cook ♦♦ commented · May 23 at 08:55 PM

However, Victron shows these elements in this schematic system which includes 40-59v batteries:

https://www.victronenergy.fr/upload/documents/3-Phase-Quattro-system-with-Cerbo-GX-Touch-50-BYD-LVL-Smart-solar-MPPT's.pdf

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Justin Cook ♦♦ pwacquiez commented · May 23 at 10:32 PM

I know, and that's unfortunate, but still the case remains that Blue Sea battery switches and Bussmann surface-mount breakers of that type (you'll note that the breaker is manufactured by Bussmann and supplied to and resold by Blue Sea) are rated for a maximum voltage of 48vDC and as such may only be used on up to 36vNom systems - while still others of the same brands and nearly identical appearance are rated only to 32 or 36vMax for use on up to 24vNom systems. This is independently verifiable on the respective Blue Sea and Bussmann product specification pages.

It is an unfortunate reality that sometimes someone drawing a schematic such as you show here (which to be clear was drawn by an independent consultant to demonstrate the fundamentals of a system, not drawn by Victron directly) does not always individually verify the specifications and limitations of all the various components shown in such a diagram, which is part of why there's an all-caps note in the bottom right corner "when in doubt always consult your dealer" or something to that effect.

Any dealer/distributor/or installer who is familiar with 50-60vDC arc length, switch contact pitting, and the limitations of magnetic arc suppression in low-voltage surface-mount breakers of that type, would recommend that this diagram be used for general reference only while substituting some of the components very generally shown with suitable replacement components such as CBi 125vDC breakers to the controllers and likely Blue Sea / Carling Technologies C-series breakers in place of the rotary battery switches (or other suitable components).

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pwacquiez Justin Cook ♦♦ commented · May 25 at 07:38 AM

on an MPPT 48V/100A: CBi QY-3(13)-D 125A is ok?

for break an MP2 which has a peak power of 27000w (600A) I don't see which of the Blue Sea / Carling Technologies C-series breakers is possible. ? (Look like 300A maximum)

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