Abstract: An apparatus and method indirectly determines the amount of outside air introduced into the ventilation system of a structure to control the indoor air quality in the structure. Test gas concentrations, preferably carbon dioxide concentrations, are measured for return air, outside air and mixed (supply) air. The flow rate of mixed air is measured. The volume of outside air introduced into the system is determined through use of the test gas concentration measurements without directly measuring the volume or flow rate of outside air. Preferably, a single sensor is utilized to measure each of the trace gas concentrations in the return air, outside air and supply air, and the various measurements sequentially multiplexed to a controller. Moreover, for calibrating the apparatus, a return air sensor is calibrated to the outside air and a mixed air sensor is calibrated to the outside air or the return air to eliminate inaccuracy due to sensor drift.

Abstract: A control system for controlling a climate control device, such as an HVAC device within a premise, utilizes real time price tier data supplied by the utility company to achieve economical temperature regulation of the premise. The control system regulates temperature based on time of day data and desired temperature data supplied by the user wherein the user may program different desired temperatures depending upon the relative cost of electricity. The system also provides billing information to the user for current usage and projected usage. The control system additionally controls appliance modules and regulates operation of the hot water heater.