It is the element affinity, or planetary rulership affinity, that counts when looking at the affinity of the Planetary Hour with a chart or a chart element (as you know I do not use Planetary Hour/ascendant as a test for radicality of a chart, but I DO use Planetary Hours for other important purposes)
In my study of the matter, it is the elemental affinity of the Planetary Hour with the ascending sign:
Hot/Dry = Fire
Hot/Moist = Air
Cold/Dry = Earth
Cold/Moist = Water
It cannot be a partial element affinity, it must be a complete affinity: eg, Mercury is of the Earth element (ascribed as such, to Earth, in Western astrology since before Ptolemy, through the time of Paracelsus and to Lilly's times) Mercury as Planetary Hour ("hour ruler") resonates with all Earth signs: thus it would resonate with Taurus, Virgo and Capricorn (if one of these signs is on the ascendant) But since Mercury is of the Earth element, it does not resonate with the element Water, even though both Earth and Water have coldness in common.
So, it is by complete elemental affinity between the Planetary Hour and the chart that affinity/resonance is determined.
The additional rulership is if the Planetary Hour is the same as the planet ruling the ascending sign, even if the elemental affinity of the Planetary Hour is different than the elemental quality of the ascending sign: eg, Venus is of the Water element; however, if Venus is the Planetary Hour and Taurus (Earth element sign) is on the ascendant, there is still resonance between the Planetary Hour and the ascending sign because that sign is ruled by Venus.
Here is a brief table illustrating the above: (PH = Planetary Hour)
+if Sun is the PH then it is affinitive to the Fire element signs of Aries, Leo and Sagittarius and is additionally affinitive as sign ruler to Leo
+If Moon is the PH then it is affinitive to the Water element signs of Pisces, Cancer and Scorpio and is additionally affinitive as sign ruler to Cancer
+If Mercury is the PH then it is affinitive to the Earth element signs of Taurus, Virgo and Capricorn and is additionally affinitive as sign ruler to Gemini and Virgo
+If Venus is the PH then it is affinitive to the Water element signs of Cancer, Scorpio and Pisces and is additionally affinitive as sign ruler to Taurus and Libra
+If Mars is the PH then it is affinitive to the Fire element signs of Aries, Leo and Sagittarius and is additionally affinitive as sign ruler to Aries and Scorpio
+If Jupiter is the PH then it is affinitive to the Air element signs of Gemini, Libra and Aquarius and is additionally affinitive as sign ruler to Sagittarius and Pisces
+If Saturn is the PH then it is affinitive to the Earth element signs of Taurus, Virgo and Capricorn and is additionally affinitive as sign ruler to Capricorn and Aquarius
...therefore, if Planetary Hour is:
-SUN = Aries, Leo, Sagittarius
-MOON = Cancer, Scorpio, Pisces
-MERCURY = Taurus, Gemini, Virgo, Capricorn
-VENUS = Taurus, Cancer, Libra, Scorpio, Pisces
-MARS = Aries, Leo, Scorpio, Sagittarius
-JUPITER = Gemini, Libra, Sagittarius, Aquarius, Pisces
-SATURN = Taurus, Virgo, Capricorn, Aquarius
Addenda:
-some have included the sign of the Planetary Hour's exaltation in the affinitive list; eg, say the Moon is the PH, it is exalted in Taurus, so if Taurus is the ascending sign and the Moon the PH there is resonant affinity; I myself do not follow this addition to Planetary Hour "lore"
-some say that if the planet of the PH is posited in a sign of which its triplicity is the same element as the ascending sign, then there is PH affinity: eg, PH is the Sun; in the chart the Sun is in Cancer, a Water element sign, and another Water element sign, Pisces, rises on the ascendant; therefore there is resonance between the PH (Sun in this case) and the triplicty related ascending sign (Pisces in this case); I also do not follow this later addition (a complicating addition to my mind) to the Planetary Hour "lore"...