Circuit breaker home charger

[Alb]

Must admit I'm also confused by the description of "burnt out".

 

[Everest]

If the EVSE is drawing 30 or 32 amps the circuit breaker should be 40 amps.

Not sure what the norm is, but mine has 40 amp protection giving plenty of headroom for a 7.2kwh charger

I believe that @Corindikev has found the problem. He says the breaker should be rated at 40Amps. I've just looked at my installation and it has a 40Amp RCBO

Not sure of the make 'W' but would suggest a better brand and 40A

I'm not a sparky but ... You should never just replace any 32A MCB / RCBO with a 40A device to "give headroom" or "because it should be more than the load".

The purpose of an MCB/RCBO is to protect the wires, not the load. The wires should be sized according to the anticipated load and the protection device should be rated to protect the wires. The carrying capacity of the wires will depend on the cross-sectional area of the conductors, heat-properties of the insulation and the installation method.

Also, the tripping characteristics of a B-curve MCB/RCBO will mean that, depending on ambient temperature, a 32A MCB will not trip until a load of approx. 1.3x its rated value is present for several hours - as shown below.

Hence, replacing a 32A breaker for a 40A breaker to give 'plenty of headroom' is absolutely not required, or desirable.

 

[Kenp1]

I never suggested just replacing with 40amp, I was just saying what my set up was,

 

[Corindikev]

The MG4 charges at 32 Amps AC. At 230 volts that is 7.4 kW. The cars internal inverter/charger has a maximum input rate of 6.6kW DC. The difference is losses due to heat and other factors.

If your circuit breaker and residual current device is 32 Amps it is at its limit and is likely to trip.

The manufacturers requirements for installation of my EVSE were to install a 40 Amp RCCB at the supply to the EVSE. This allows for spikes and surges. The maximum the EVSE will operate at is 32Amps AC though I am able to limit the input as required from 6 to 32 Amps.

 

[Everest]

The MG4 charges at 32 Amps AC. At 230 volts that is 7.4 kW

Interesting - maybe the specification is different in Australia? The UK specification from MG is a maximum AC charge rate of 7kW, not 7.4kW.

If your circuit breaker and residual current device is 32 Amps it is at its limit and is likely to trip.

No, It is not likely to trip - please refer to the curve-B tripping graph in post #22 above. A 32A MCB will not trip until at least 40A is passed through it and then, only after about 3 hours usage.

The manufacturers requirements for installation of my EVSE were to install a 40 Amp RCCB at the supply to the EVSE.

Not sure what your point is here? An RCCB does not 'trip' or protect a circuit from an over-current situation. An RCCB only provides protection for earth leakage faults. Its 40A rating specifies the maximum current that may pass through it and, as such, that rating must always be higher than any MCB/RCBO or DNO head-end fuse that protects the circuit it is on.

 

[siteguru]

The MG4 charges at 32 Amps AC. At 230 volts that is 7.4 kW. The cars internal inverter/charger has a maximum input rate of 6.6kW DC. The difference is losses due to heat and other factors.

If your circuit breaker and residual current device is 32 Amps it is at its limit and is likely to trip.

The manufacturers requirements for installation of my EVSE were to install a 40 Amp RCCB at the supply to the EVSE. This allows for spikes and surges. The maximum the EVSE will operate at is 32Amps AC though I am able to limit the input as required from 6 to 32 Amps.

I agree with @Everest.

The maximum I've ever seen my EVSE deliver to my MG4 is 7.2kW (per the Wallbox app), with the car drawing 6.5kW at that same time. (I presume that was 6.5kW into the battery, and the rest was losses and auxiliary supplies).

 

[wattmatters]

The maximum I've ever seen my EVSE deliver to my MG4 is 7.2kW (per the Wallbox app), with the car drawing 6.5kW at that same time.

Looking over a few months of data, the most my EVSE drew from the AC supply was 7.2x kW, with the car reporting a DC charge rate of 6.4 kW. Peak power draw recorded (by my Iotawatt at the circuit board) in last 12 months was 7.25 kW.

My EVSE never reports operating at more than 31 A even when set to charge at up to 32 A. I'd say that's because of a limitation of the car's on-board charger.

Site voltage will also play a part. Where I am now voltages are stubbornly high at 245-255 V. When voltage is high the system needs less current.

In Australia it's probably best not to speculate on the installation requirements, leave it to the professionals as there are multiple factors in play and each installation has difference requirements (board capacity, distance to EVSE, environmental factors, cable routing and protection etc).

Some guidance here:

https://electricvehiclecouncil.com.au/wp-content/uploads/2024/02/EVSE-installation-guideline.pdf