Harold Halewijn avatar image
Harold Halewijn asked

ESS selectivity and circuit breakers

Hi All,

today I had a short circuit in the Critical Loads section on my ESS. All circuit breakers in between grid and the short circuit switched off. Whereas I was expecting that only the circuit breaker of the circuit itself should be switched off.

now I’m searching for some design rules to better design selectivity in case of ESS.

The connection to the grid is made by 25A fuses (3 phase). So to maintain selectivity I have a 3P-16A circuit breaker between the switch board and the Multi’s. I estimated that adding an ESS creates its own energy system but now I realize that under normal circumstances the relais between grid input and Critical Load output is closed. Following the NEN1010 selectivity rules I then have to use 10A circuit breakers to individual circuits. But that means I have to swap my complete household switch board because it now contains 16A circuit breakers which is quite normal in Holland. And it also leaves me in a non preferred situation since 10A is far to low for some off the systems I’m using (dishwasher, etc.).

I have systems on the non-critical side of ESS like EV, heat pump and so on. They have there own 16A circuit breakers.

Perhaps someone can help me with some suggestions to create a save and reliable system? Or is what I described the way to go (using selectivity and see the multi as a intermediate device).

kind regards,


ESSBattery Protect3 phase
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1 Answer
seb71 avatar image
seb71 answered ·

The MCBs should be chosen based on the wiring (how many amps a certain circuit can safely carry).

Use bigger wires (greater section) and then you can use MCBs with higher amperage values.

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Harold Halewijn avatar image Harold Halewijn commented ·

Certainly not; MCB‘s are mandatory to safeguard the total installation. Proper MCB sizes are part of standardization rules. The problem is that under normal circumstances and according to the rules every device should be secured by a MCB. And following the rules that MCB should me sized Grid_connection divided by 1.6. So 25A/1.6=16A at AC-input of the Multi. And then again 16A/1.6=10A at the AC output of the device.

By doing this we loose a lot of power! I‘m curious how other people do this.

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seb71 avatar image seb71 Harold Halewijn commented ·

MCBs are used to protect the wires, not the appliances/devices.

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