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 ³He(e^-,ν_e)³H(p,γ)⁴ is considered. At the distance of 1 a.u., the flux of tritium neutrinos is equal to 8.1 × 10⁴ cm^-2·s^-1. It is an order of magnitude higher than the flux of the (hep)-neutrinos. Radial distribution of ³H-neutrinos yield inside the Sun and their energy spectrum which has a form of line at the energy of (2.5 - 3.0) keV are calculated. The flux of thermal tritium neutrinos is accompanied by a very weak flux of antineutrinos (~10³ cm^-2·year^-1) with energy lower than 18.6 keV. These antineutrinos are produced during Urca processes ³He³H. 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.