In this paper, much attention is given to lines of minimum and maximum neutrino energies. Tritium chain of the hydrogen cycle in the Sun including reactions of     3 3 e He e , H p, He    4 is considered. At the distance of 1 a.u., the flux of tritium neutrinos is equal to 8.1 × 10 4 cm −2 ·s −1 . It is an order of magnitude higher than the flux of the (hep)-neutrinos. Radial distribution of 3 H-neutrinos yield inside the Sun and their energy spectrum which has a form of line at the

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... y of (2.5 -3.0) keV are calculated. The flux of thermal tritium neutrinos is accompanied by a very weak flux of antineutrinos (~10 3 cm −2 ·year −1 ) with energy lower than 18.6 keV. These antineutrinos are produced during Urca processes 3 He 3 H. The flux of the neutrinos of maximum possible energy (line 19.8 MeV) produced due to the (heep)-reaction (related to the (hep)-process) is estimated.