Cable sizing

Hi all,

I am trying to calculate a SWA 4 core that will be protected by a 250 amp switched fuse isolator. It is going to supply a 3 phase electric boiler that pulls 209 amps each phase at most. I'm filling in the parameters to an online cable calculator ,when asked for the voltage i've put 400 v, when asked for load in amps i've put 250 amps. Is this correct or should i be putting the total amps 627 because thats the total 3 phase load?

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