Hi everyone,
I’m running an ESS system and need help with an external current sensor issue that’s causing exactly double current readings on a 3-phase, parallel MultiPlus II setup.
System configuration
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3-phase VE.Bus system
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2 × MultiPlus II 48/3000/32 per phase (6 units total)
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Each phase master has an external current sensor (CT) connected
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CTs are located right after the grid meter, before splitting to the inverter pair
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VE.Configure: “External current sensor connected” enabled on each phase master
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ESS Assistant active (grid-connected mode)
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INT–COM jumpers removed on all slaves — leaving them in caused power measurement errors
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Cerbo GX + VRM monitoring
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3-phase AC-coupled PV on AC-OUT, but problem existed before PV connection
Problem
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Grid current (A) shown on Cerbo GX and VRM is exactly double the real value (verified with clamp meter)
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Power (kW) readings are correct
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ESS grid-limit and set-point must be multiplied by 2 for the system to behave normally
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It seems the current from each phase’s CT is being counted twice — maybe by both master and slave, or by VE.Bus aggregation logic
What I’ve checked
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CT wiring and polarity — OK
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Only masters have “external current sensor” enabled
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Correct CT orientation (grid → inverter)
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Firmware up to date
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Same behavior whether PV is connected or not
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Found this similar thread but no definitive answer:
What is the correct current sense configuration for parallel MultiPlus II?
Questions
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In a parallel MultiPlus II setup (per phase), what is the correct configuration for external current sensors so that only the master’s CT is used in ESS calculations?
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Should slaves keep the INT–COM jumper (internal CT) or should it be removed when the master uses an external CT?