  We investigate the derivation of Friedmann equations in Rainbow gravity
following Jacobson thermodynamic approach. We do not restrict the rainbow
functions to be constant as is customarily used, and show that the first law of
thermodynamics with a corresponding `classical' proportionality between entropy
and surface area, supplemented eventually by a `quantum' logarithmic
correction, are not in general sufficient to obtain the equations in flat FRW
metrics.
