[en] Required conditions for Ohmic ignition of a RFP reactor are estimated using a simple energy balance equation. It is found that for the ignition at the poloidal field of 5T the energy confinement time achieved in a tokamak must be at least necessary. It is pointed out the heating up of the first wall in the setting up phase is very crucial. In order to save that a larger generator power than 10 GW seems to be required. (author)