From the instruction manual linked to the product webpage above:
ELECTRICAL INFORMATION:
The Hawaii 2000 is not supplied with a plug and is intended for connection to the fixed wiring. Installation must only be carriedout by competent persons or a qualified electrician according to national regulations and the unit must be earthed. The electricalsupply to the unit should be provided by connecting to a current protection device suitable for the electrical rating of the unit inaccordance with Table 1 and providing disconnection in both poles. All fixed wiring must have sufficient capacity to carry thecurrent required by the heater.
An electrical plug may be added by the installer so long as both the plug and electrical supply circuit to be plugged into areappropriately rated according to the requirements of the heater in Table 1 and in accordance with local regulations. Any extensionlead used must have sufficient capacity to carry the current required by the heater. All plugs, sockets and switches intended foruse outdoors must have an appropriate water ingress protection. Always disconnect the heater from the power when not in use.