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Roman Štembera avatar image
Roman Štembera asked

Is Multiplus II 3000/48V 35 capable of transferring 45Amps?

Hi, can anyone explain max current the Multi is capable to transfer. The manual says:
multiplus-ii-3000-48v-45a-ttransfer.png

I have opened the Multiplus case and I see only 32 Amps relays there:

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20210309-220346.jpg

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From the photos above you can see there are only 32Amps relays. I think the relays will blow up in the case the Multi will add its 13 Amps to the 32Amps on AC-In.

Is the manual stating wrong numbers? I have searched the specs of the relays and it seems they are not able to handle 45 A even for short period of time.


Can someone explain why the 32 relay is used when Victron declares that it should handle max 45 Ams? How to size the circuit breaker here? I think 32A circuit breaker should be enough in the case 32 Amps relays are used internally by Multi.

Multiplus-IIMultiPlus Quattro Inverter Charger
multiplus-ii-3000-48v-45a-ttransfer.png (60.9 KiB)
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20210309-220346.jpg (640.7 KiB)
20210309-220402.jpg (724.0 KiB)
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2 Answers
Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

The transfer relay is rated for 32A the additional 13A from the Multi are behind the transfer relay.

mp-ii-transfer.png

The breaker at the AC input should be rated for 32A.


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Roman Štembera avatar image Roman Štembera commented ·

Yes. But the AC OUT2 is behind 32 Amp relay so I think it can be overloaded in full load situation when there is no consumption on AC out 1. What CB to put on AC OUT2? Isnt it design problem to have only 32Amp relay on AC out 2 while transferring 45 Amps here?

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Roman Štembera avatar image
Roman Štembera answered ·

The design of Multiplus II 3000 is wrong. AC-OUT-2 relay can burn out in the case the 45 Amps is transferred only to the AC-OUT-2. I think there should be 45 Amps relay on AC-OUT-2. I have asked Victron representative and he has redirected me to the forum considering previous answer from @Matthias Lange - DE as correct. @Matthias Lange - DE - please review your answer.

Until resolved, I need to put 32 Amps CB to the AC-OUT-2 to protect the relay. Please beware of attaching the 45 CB to the AC-OUT-2. This can lead to the situation where the AC-OUT-2 relay is overloaded with 45 Amps as it is designed only for 32 Amps. See the picture below - the purple current flow is dangerous.19352-mp-ii-transfer.png


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Matthias Lange - DE avatar image Matthias Lange - DE ♦ commented ·

I never wrote something about AC OUT 2 and also the manual never says that you can use 32A+13A at AC OUT 2, that only applies to AC OUT 1.

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Roman Štembera avatar image Roman Štembera commented ·

I have just bought the additional Multiplus II 3000/48. It comes with HW revision 18 (the problem was detected on HW rev 15). Inside of HW Revision 18, there is 32Amps relay on the AC-OUT2 replaced by Panasonic 40A relay with doubled contacts(see the picture attached).

1622724143799.png

(I guess internal wiring is to have the AC-OUT2 relay using the two contacts in parallel to achieve 80A). It seems that from HW revision 18 the problem is fixed.

I have question: Is it possible to put these two HW revision (HW15 + HW18)in parallel?

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