  Quantum-mechanical system -- spin 1 particle in external Coulomb field is
studied on the base of the matrix Duffin-Kemmer-Petiau formalism with the use
of the tetrad technique. Separation of the variables is performed with the help
of Wigner functions. With the help of parity operator, the radial 10-equation
system is divided into two subsystem of 4 and 6 equations that correspond to
parity P=(-1)^{j+1} and P= (-1)^{j} respectively. The system of 4 equation is
reduced to a second order differential equation which coincides with that
arising in the case of a scalar particle in Coulomb potential. It is shown that
the 6-equation system reduces to two different second order differential
equations for a "main" function. One main equation reduces to a confluent Heun
equation and provides us with energy spectrum. Another main equation is a more
complex one, and any solutions for it are not constructed.
