A heat capacity spectroscopy HCS setup (3 omega method) adapted to measure glass transitions in polymers is described. Sample contacting and signal sensitivity are improved so that the relevant complex heat capacity in a (0.2-2000) Hz frequency region can be recorded down to relative heat capacity steps Delta c(p)/c(p) of a few percent. Linearity and Kramers-Kronig consistency tests are described. The influence of heater width and sample thickness is discussed. The possibilities of the instrument are demonstrated for the glass transition in natural rubber, polystyrene, and a random copolymer of n-butyl methacrylate and styrene.