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Lindsay avatar image
Lindsay asked

Is it possible for the 5KVA MultiPlus -II to draw maximum power (9KW) without PowerAssist?

Hello,

Reason being, when the 2 loads are connected, 2 machines (LO5 Screw Air Compressor & Oven) and the grid is off the MCB for L1 is tripping, This happens so quick that it's not displayed on the AC consumption graph on the portal, however before tripping i can see it's drawing a power of +15KA also L2&L3 MCBs don't trip.

In the Victron Energy Blue Power manual page 10 it says for a 5KVA a 50A rated MCB must be used, can I up the MCB rating? (I think not but it's just for a few seconds for the initial intake draw) or I can still use a 50A rated MCB but with a higher breaking capacity (from a 10KA to a 15KA) will that help?

Here's the connection:

It's a three phase system with 5KVA| 70-50 MultiPlus-II Victron Inverters using a Freedom Won Battery LifePO4 Lite Home 52V 20KWH. From the battery it goes to the busbar from busbar to the 50A MCB (for each line) from the MCB to the inverter.


Thank you


Multiplus-II3 phasepowerassist
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Alexandra avatar image Alexandra ♦ commented ·
@Lindsay

It will alsways try to power assist if you have ESS on the system.


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Lindsay avatar image Lindsay Alexandra ♦ commented ·

@Alexandra but what if ESS is not on the system (like there is power outage)

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Alexandra avatar image Alexandra ♦ Lindsay commented ·

@Lindsay

If you are invertering then your limit is its inverting power.

The multi 2 can do a short overload of 9000w while in erting if your system has been sized and built correctly.

But if you are tripping a 50A that is 11500w load (technically higher if it is a c trip curve), unless your breaker is developing a problem. So that load is too high.

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Lindsay avatar image Lindsay Alexandra ♦ commented ·

@Alexandra

We using a C curve single pole MCB

Brand- :hager NFN150

Current Rating 50A

Breaking Capacity 10KA

see image of the compressor at it's peak intake

Reading of the oven at it's peak


see the compressor at it's peak intake

1674122307124.png

the problem occurs when they both get switched on ,,, but individually and or with other loads it's fine. It's just when they together.

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Alexandra avatar image Alexandra ♦ Lindsay commented ·

The thing with the VRM is the logging is second second interval, so the peak may be much higher than what you are seeing in the screenshots. And you also cannot see the power factor there.

What current is being drawn at this point? It may be worth putting a clamp meter on and checking what is happening.

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3 Answers
jwfrary avatar image
jwfrary answered ·

What's the rating of the MCB your using?

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Lindsay avatar image Lindsay commented ·

@Jwfrary

Current Rating 50A (single pole connected to L1 of the inverter)

Breaking Capacity 10KA.



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Alexandra avatar image
Alexandra answered ·

@Lindsay

You describe the MCB being used in the DC side of the inverters.

Just wondering if you are aware that the recommended fuse and cable size on the 5kVa MP2 is found here and is 70mm² with a 200A fuse?

So it is undersized if i understand correctly and is being used on the DC. And it tripping correctly as 48v * 50A is 2400W where the load actually (shown in your screenshots) is just over that. 50A is the AC cable recommended size.

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Lindsay avatar image Lindsay commented ·

@Alexandra The Freedom Won battery we using comes with it's cables and protection, so the connection is from the battery cables to BusBars. Cable size are 2× 50mm^2 red cable & 2× 50mm^2 black cable (see battery type below)

1674467872110.png

The 50A MCBs I was referring to are in regards to this:

1674467927808.png

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Alexandra avatar image Alexandra ♦ Lindsay commented ·

Putting in a bigger breaker is not a totally wise course of action.

50A @ 230v is 11500kva your loads should not be tripping that. So there is a fault there.

So you need to find out the reason for the tripping. Is is fault related? A fault with wiring or the breaker?

Have you tried a tong test? Is the breaker next to another breaker which is causing a thermal trip?

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Alistair Warburton avatar image
Alistair Warburton answered ·

It isnt a good idea to have a 3 phase system with individual MCB,s on ths AC, a 3 phase breaker should be used.

In round figures a 5KVA Multi will do circa 4kW, twice that for a short period. Supplying a 3 phase load that would be 12kW, 4 per phase, and again twice that for a short period.

I too am confused where this 50A MCB is?
Is/are the problematic load/s three phase or single phase?

Can you post a system diagram?

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Lindsay avatar image Lindsay commented ·

@Alistair Warburton this is the system:

1674545784433.png

just the solar system that's not yet connected.

bellow is where the 50A is located (incase it's not clear when zoom):

1674546214236.png

The first load is a full on 3 phase (it's the one that draws the most) the second one (the compressor) is a three phase too but also a single phase for the fan


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daniel-feist avatar image daniel-feist Lindsay commented ·

I think you (or your system designer/installer) are mixing up the AC-in breaker requirements and the DC fuses!

Between your bus bar and inverters, you should be using 200A fuse as detailed on page 13 of the manual. A 50A AC breaker is required for AC-in, as detailed on page 13 of the manual.

50A at 50v is 2500W, which is less than a third of the inverter's max power of 9000W so not surprising it trips.

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Lindsay avatar image Lindsay daniel-feist commented ·

@Daniel Feist Thank you so much, this make so much sense don't know how we overlooked that part.



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Lindsay avatar image Lindsay daniel-feist commented ·
@Daniel Feist Can i replace the 50A MCBs with 80A MCBs (80*52=4160A) while waiting to put the 200A fuse? cause i already have the 80A MCBs



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daniel-feist avatar image daniel-feist Lindsay commented ·

I don't see why not. The MCBs should be suitable for 60V DC and non-polarized to suitable though.

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Lindsay avatar image Lindsay daniel-feist commented ·
@Daniel Feist ok thank you.
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