This is a question many people are asking.

I have been installing relay to suit the neutral conductor

5 kva = a 25 amp relay

8 KVA = 40 amp relay

Do you really need a 20/25 amp relay/contactor for a 5 kva unit?

or a 32/40 amp realy/contactor?

IF you have a 4 mm neutral wire then you should have a 32 amp relay.