stebel nautilus thicker wire, relay?

I am planning to install a Stebel Nautilus air horn to a 6Y Skoda Fabia (same electrical system as 6N Volkswagen Polo). The new horn says a 20a fuse is used for it, and a relay is provided. The wiring diagrams for the car show that the default fuse for the standard horn is a 20a fuse, and that the wire cross-section for power and ground supplying the horn is 1.5mm squared (equates to approx 15AWG). My thinking is if the standard fuse is 20a then perhaps the standard wiring should be able to cope with powering the horn and perhaps I do not need the supplied relay and higher gauge wire?

Thanks in advance.

If you can verify that the fuse supplies the horn circuit alone, then yes you will be fine!

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COMMIT YOUR WAY TO JEHOVAH AND HE WILL ACT IN YOUR BEHALF. PSALMS 37:5

Just tap the standard horn's leads and wire to your compressor. By the way telling them it's a Polo makes no difference, even the Golf is a Rabbit, the Bora is a Jetta and the Skoda might as well be a SEAT!