  Higgs triplet models are known to have difficulties obtaining agreement with
electroweak precision data and in particular constraints on the $\rho$
parameter. Either a global $SU(2)_L \otimes SU(2)_R$ symmetry has to be imposed
on the scalar potential at the electroweak scale, as done in the well-known
Georgi-Machacek (GM) model, or the triplet vacuum expectation values must be
very small. We construct a supersymmetric model that can satisfy constraints on
the $\rho$ parameter, even if these two conditions are not fulfilled. We
supersymmetrize the GM model by imposing the $SU(2)_L \otimes SU(2)_R$ symmetry
at a scale $\mathcal M$, which we argue should be at or above the messenger
scale, where supersymmetry breaking is transmitted to the observable sector. We
show that scales $\mathcal M$ well above 100 TeV and sizable contributions from
the triplets to electroweak symmetry breaking can be comfortably accommodated.
We discuss the main phenomenological properties of the model and demonstrate
that the departure from custodial symmetry at the electroweak scale, due to
radiative breaking, can show up at the LHC as a deviation in the `universal'
relation for the Higgs couplings to $WW$ and $ZZ$. As a by-product of
supersymmetry, we also show that one can easily obtain both large tree-level
\emph{and} one loop corrections to the Higgs mass. This allows for stops that
can be significantly lighter and with smaller mixing than those needed in the
MSSM.
