Embodiments provide a shell module that accommodates form factors that define operational and aesthetic aspects of a modular device. The control circuit has a thermally biased low outlet thermostat and a thermally biased high outlet thermostat which control the energization of a heater in the dryer. The method further includes the steps of updating the minimum voltage value to the current voltage value when the current voltage value isn’t greater than the maximum voltage value, and updating the maximum voltage value to the current voltage value when the current voltage value is greater than the maximum voltage value. The accelerator control circuit has an accelerator control switch.