How do I calculate the power consumption of an industrial dishwasher?

P = 3 * Uf * If

or

P = square root(3) * Ul * Il

Here are:

Uf: phase voltage

If: phase current

Ul: line voltage

Il: line current

(* is multiplication)

In electrical engineering, the formulation with line quantities is usually preferred, so:

P = square root(3) * Ul * Il

We have for the line voltage Ul = 400 V.

So for Il we find:

Il = P / (root(3) * 400 V) = 18.8 A.

(By the way, I assumed that in your question you meant a mains voltage of 3X400V. 230V is the phase voltage, but if we are feeding 3 phase, we are using the line voltages of 400V.)

We now have the active component of the current, but to find the total current we still need to divide by the power factor. The power factor of a dishwasher seems to me to be very close to 1, because the energy is mainly used for heating. So I suppose that cos phi = 0.95

So for the total current I find: I = 18.8 A / 0.95 = 19.8 A.

In principle, you can therefore secure the circuit with a 4-pole 20A circuit breaker. Since it’s quite tight, I might be tempted to go for a 25A caliber.

On the basis of this last selected normalized current you can determine the cross-section of your pipe.