The power module may be used in conjunction with the DITRA-HEAT-E-RT or DITRA-HEAT-E-R thermostats when the heating load exceeds 15 amps (e.g., in large floor applications) to maintain a single point of control. Up to 16 DITRA-HEAT-E-RR power modules may be connected in series via low voltage signal wire to a single DITRA-HEAT-E-RT or DITRA-HEAT-E-R thermostat.