Off the beaten track of scalar singlet and doublet extensions of the Standard
Model, triplets combine an interesting LHC phenomenology with an explanation
for neutrino masses. The Georgi-Machacek model falls into this category, but it
has never been fully explored in a global fit. We use the {\texttt{HEPfit}}
package to combine recent experimental Higgs data with theoretical constraints
and obtain strong limits on the mixing angles and mass differences between the
heavy new scalars as well as their decay widths. We also find that the current
signal strength measurements allow for a Higgs to vector boson coupling with an
opposite sign to the Standard Model, but this possibility can be ruled out by
the lack of direct evidence for heavy Higgs states. For these hypothetical
particles, we identify the dominant decay channels and extract bounds on their
branching ratios from the global fit, which can be used to single out the decay
patterns relevant for the experimental searches.Comment: 23 pages, 4 figures. In v2: 30 pages, 6 figures. Updated Higgs
experimental data. Global fits updated. Major conclusions unchanged. In v3:
28 pages, 6 figures. Comments on other searches included in summary. Version
accepted for publication in PR