Low voltage question using EV car charger and elec shower

Calahonda52

Domestic MIC is 12

Car charger, with load management via CT back to main incomer, was drawing 6.8 kW.

Electric shower, 7.8 kW came on.

Later I noticed car charger stopped, went out Low voltage message voltage 202 V

Not certain it happened when the shower started but just wondering....

Will repeat the exercise later.

Thanks as always

kirk.

You don't draw wattage you draw amps

200v is too low always if that's correct

If car charger is supplied from the cabinet it's probably a supply issue

If not could be an issue at main board

kirk.

Usage is always in watts

Capacity is KVA or amps

You draw amps never killowatts

Calahonda52

Perhaps for the experts you are correct. I dont know.

However for the ordinary punter, I have an app on the phone which tells me now that the car is charging at the rate if 1,3 kW, and since the session started I have added 1.43 kWh

If I understand it correctly for SP, Volts by amps is watts.

So if the "breaker" is rated at 32 A and we work with 240 V, then we are at kW of 7,680 watts

or a 13 amp plug will give me a limit of 3.12 kW

I just did it now again, car was pulling 6.8 kW, turned on the shower, car dropped back to 5.2 kW and back up to 6.8 kW when I turned it off.

10-10-20

So here's my theory...

On a normal day the charger is pulling near to 6800w at 235v (assuming you're getting 235v): 6800w/235v = 29.6A.

When the shower goes on the voltage is dropping due to the lower resistance of the circuit but the charger will still try pull a preconfigured amount of amps (as it's configured to pull a current, not a wattage), therefore: 5200w/202v = 25A.

So yeah, if you're measuring 202v when the shower and EV charger are running, then it looks like you're seeing an unacceptable voltage drop. Time for a rec to look into the fault.

kirk.

You're dealing with gadgets here so you can't assume anything about voltage until it's reliably tested

200v anywhere in a 230v installation is always too low

Checking voltage drop is a 5 minute job

Simulate same conditions and time of day and check supply voltage at cabinet to see if it's a supply issue

If it's 200v at cabinet isolator you ring ESBN

If not check main board for issues usually heat damage and connections and check voltage in installation

kirk.

If you've got nightstorage heating or other stuff like heatpumps then you might need an upgrade to 16 kva

I know nothing about car charging but 12kva was ok for about 6kva of night storage load

Car charging on its own should be ok with the shower on 12kva imo.

Volt drop then can be an issue then if supply capacity is ok for the loads in the premises

There may not be any faults on supply or installation but the voltage drop is just excessive on the supply lines especially rural premises

Calahonda52

Sparks coming out next week, could be an estate supply issue