FA-92503 / HVAC thermostat control / Member archive

Celsius arrow press steps from a truncated half degree · case 03

The first press after switching to C sometimes leaves the displayed value unchanged or jumps the wrong way.

Member previewVariant 3 · 3 implementations · 8 checks per implementation

Case contract

Thermostat setpoint keypad. The setpoint is stored in tenths F. In C mode the display shows the stored value converted to C and rounded half up to 0.5 C; a press moves the displayed value by 0.5 C and stores exactly 320 + half_degrees*9 tenths F. In F mode the display rounds half up to whole F and a press moves the whole-degree value by 1 F. After each press the stored value is clamped to 45.0-90.0 F. Return [display, stored_tenths_F] per press.

Why this case matters

Residential and light-commercial thermostats make these decisions sample by sample; each defect changes equipment calls in a way that shows up as short cycling, comfort complaints or equipment stress.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
regression: scenario 56	`[["7.0", 450], ["7.0", 450], ["7.5", 455], ["7.0", 450], ["7.5", 455]]`	`[["7.5", 455], ["7.0", 450], ["7.5", 455], ["7.0", 450], ["7.5", 455]]`	Failed

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