Abstract: Systems and methods are described for synchronizing an HVAC control system. A method, includes: a synchronization sequence including: reading a base time from an internal clock at a first time and saving the base time; measuring an elapsed time interval, from the first time to a second time, by counting an external clock using a frequency counter; and then resetting the internal clock to the base time plus the elapsed time.

Abstract: Systems and methods are described for an adaptive hierarchy usage monitoring HVAC control system. A method, includes: regulating user access to at least one menu of an interactive user interface of a programmable digital thermostat, including: reversibly defining at least one minimum user level required to access the at least one menu.

Abstract: Systems and methods are described for a HVAC control system. A method, includes regulating user access to an interactive user interface of a programmable thermostat, each user identified by a personal identification number associated with a user type such as, for example, building owners, maintenance personnel, building tenants, and manufacturers.

Abstract: A collapsible tub insert utilizes a unitary element having a base portion and walls upstanding therefrom. One portion of the walls includes a semi-rigid construction joined by an accordion pleated wall portion, similar to a "living-hinge" to the remaining semi-rigid wall portion. One of the wall portions includes an opening extending downwardly from the marginal edge thereof communicating to the interior of the enclosure defined by the wall and the base, the base material adjacent the accordion pleated area of the side wall portion is pleated permitting the pair of semi-rigid portions to be fully collapsed or to extend outwardly at selected locations, utilizing a spacing bar therefor. A drain hole communicates to the exterior of the collapsible insert.