RCBO to inverter advice please

[lakelandfolk]

Hello, planning to upgrade our 3 kW inverter to a 5 kW model. Existing connection to the CU is via 2.5mm cable, only 500mm long,  and 20 amp RCBO. Do they need to be increased to cope with the 5kW load?

[Jenki]

5KW is around 35amp on mains 240 voltage. 

2.5mm Sq cable can take around 25Amp load

so yes to both.

[lakelandfolk]

Thanks Jenki, so 4mm cable and 32a RCBO??

[Dillsue]

3 hours ago, Jenki said:

5KW is around 35amp on mains 240 voltage. 

Are you sure? AFAIK rule of thumb is 4 amp per kw so 5kw is circa20amp. Likely easily handled by 2.5mm cable over half a meter, but..... If youre going to increase the RCBO rating to 32amp, youll need to increase cable size. 

Edited February 2, 2023 by Dillsue

[Jenki]

14 minutes ago, Dillsue said:

Are you sure? AFAIK rule of thumb is 4 amp per kw so 5kw is circa20amp. Likely easily handled by 2.5mm cable over half a meter, but..... If youre going to increase the RCBO rating to 32amp, youll need to increase cable size. 

NO. 🙊  not sure where I got 35A from.   so as you said it is around 20-22A cable is ok to 27A  

 

@lakelandfolk. Please ignore my brain fart above.. 

[lakelandfolk]

OK, thanks

[Mattg4321]

5kw is 21.7 amps at 230v or 20.8 amps at 240v. 
 

Assuming 2.5mm2 is twin and earth, this can take up to 27 amps if ref method C - clipped direct. 
 

You may be able to get a 25 amp RCBO for your consumer unit. Guessing someone will be wiring in the new inverter though, so why not let them deal with it?