Is there any need for temperature control, perhaps from a thermostat? If so, then yes, some form of starter/contactor is needed to connect between the tiny switch currents in the thermostat and the heavy currents needed for the 54kW.
If there is no need for temperature control, and there is a circuit breaker that will take the starting currents then there is no need for a starter as well.
Bear in mind that the Regulations for electrical installations near swimming pools are very concise as to what is and what isn't allowed. If in any doubt, consult a qualified Electrician.
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The elephant is a funny bird. It flits from bough to bough. It lays its eggs in a rhubarb tree and whistles, like a cow - Spike Milligan.
