  We analyze conditions for the observation of a low energy SU(4) fixed point
in capacitively coupled quantum dots. One problem, due to dots with different
couplings to their baths, has been considered by Tosi, Roura-Bas and Aligia
(2015). They showed how symmetry can be effectively restored via the adjustment
of individual gates voltages, but they make the assumption of infinite on-dot
and inter-dot interaction strengths. A related problem is the difference in the
magnitudes between the on-dot and interdot strengths for capacitively coupled
quantum dots. Here we examine both factors, based on a two site Anderson model,
using the numerical renormalization group to calculate the local spectral
densities on the dots and the renormalized parameters that specify the low
energy fixed point. Our results support the conclusions of Tosi et al. that low
energy SU(4) symmetry can be restored, but asymptotically achieved only if the
inter-dot interaction $U_{12}$ is greater than or of the order of the band
width of the coupled conduction bath $D$, which might be difficult to achieve
experimentally. By comparing the SU(4) Kondo results for a total dot occupation
$n_{\rm tot}=1$ and $n_{\rm tot}=2$ we conclude that the temperature dependence
of the conductance is largely determined by the constraints of the Friedel sum
rule rather than the SU(4) symmetry and suggest that an initial increase of the
conductance with temperature is a distinguishing characteristic feature of an
$n_{\rm tot}=1$ universal SU(4) fixed point.
