A nut includes a bottom wall adapted to be connected fixedly to a printed circuit board, and an annular surrounding wall extending integrally from a periphery of the bottom wall away from the printed circuit board, having a threaded inner wall surface, and cooperating with the bottom wall to define a threaded blind hole for engagement with a bolt. The HVAC controller may calculate a transient heat rise value that is based upon a powered time period and a first order time lag, especially during a time period before which the HVAC controller reaches a steady state temperature condition. This improved tube is especially beneficial as it provides for greater working efficiency, preservation of catalytic materials, straightforward maintenance and replacement procedures, and effective isolation of unwanted particles. When the power is switched on, the second exposure information D2 is selected for supply to a timing control circuit. The system also includes an annular shoulder formed between the anchoring portion and the abutment receiving portion.