We study the effect of electron hopping in triple quantum dots modeled by the three-impurity Anderson model. We determine the range of hopping parameters where the system exhibits the two-channel Kondo effect and has non-Fermi-liquid properties in a wide temperature interval. As this interval is entered from above, the conductance through the side dots increases to a half of the conductance quantum, while the conductance through the system remains small. At lower temperatures the conductance through the system increases to the unitary limit as the system crosses over to the Fermi-liquid ground state. Measuring the differential conductance in a three-terminal configuration provides an experimental probe into the NFL behavior.