In theory, the North Star can be seen from anywhere north of the 1 degree north latitude line. If you are actually on the equator, note that the north star, Polaris, is almost 1 degree from the actual celestial north pole, and so it would rise and set.
Given the refraction of the atmosphere, when you see a star setting (or rising) it is actually a bit below the geometrical horizon, so you will be able to see the north star a bit farther south than you could without refraction.
The final aspects of this are that when a star is at the horizon, its light is dimmed more than when it is higher in the sky because of the additional atmosphere the light must pass through. Couple this with the usual effects of light polution being more significant at lower altitudes, this makes the north star hard to see south of latitude 15 to 20 north, based on my own observations at sea.
(Clear, night skies are needed. The north star isn't one of the brightest in the sky, although it is the brightest star for some distance from the north celestial pole.)