## 5 Results
### Virtual Sensor Fault-Correction Effect
#### 5.2.1 Indoor Set-Point Temperature Unmet Hours  
The distribution of supply chilled water, air supply, indoor temperatures, and indoor set-point temperature unmet hours were analyzed to evaluate indoor thermal comfort  
Figure 8: Results of fault detection with various time-series data: (**a**) Case A-1 (Point, offset: \(-3\)); (**b**) Case A-2 (Point, offset: \(3\)); (**c**) Case B-1 (Fixed, offset: \(-3\)); (**d**) Case B-2 (Fixed, offset: \(-1\)); (**e**) Case B-3 (Fixed, offset: 1); (**f**) Case B-4 (Fixed, offset: \(-3\)); (**g**) Case C (Random, offset: \(-3\) to \(3\)); (**h**) Case D-1 (Drift, offset: \(-0.1\)\({}^{\circ}\)C/h); and (**i**) Case D-2 (Drift, offset: \(0.1\)\({}^{\circ}\)C/h).  
The impacts on indoor set-point temperature unmet hours and the distribution of supply chilled water, air supply, and indoor temperatures in Cases A-1 and A-2, where sensor faults occurred once a week for one hour, were comparable to those of the normal case (Figures 9 and 10). The impact on indoor thermal comfort varied depending on the frequency and offset of temporary fault occurrences because these cases assumed that the sensor faults only occurred for one hour per week. The fixed-offset cases (Cases B-1 and B-2) experienced faults with negative offsets in the SCWT sensor, resulting in increased distributions of the supply chilled water and supply air temperatures compared with those of the normal case (Figure 9,b). Consequently, indoor temperature distribution increased, leading to approximately 12.6 and 0.1 h increases in indoor set-point temperature unmet hours (Figures 9c and 10). In contrast, Cases B-3 and B-4 had faults involving positive offsets in the SCWT sensor, which did not significantly impact the indoor set-point temperature during unmet hours or distributions of the chilled water supply, supply air, and indoor temperatures (Figures 9 and 10). Case C involved random sensor fault offsets that exhibited differences in the distribution of SCWT compared with that of the normal case. However, the supply air and indoor temperatures showed similar distributions (Figure 9). Consequently, indoor set-point temperature unmet hours increased by approximately 0.4 h (Figure 10). Among the drift offset cases, Case D-1 had a negative sensor fault offset, which resulted in a significant increase in the distributions of the supply chilled water, supply air, and indoor temperatures compared with those of the normal case (Figure 9). Consequently, the indoor set-point temperature unmet hours increased by 106.6 h (Figure 10). In contrast, Case D-2 had a positive sensor fault offset, which exhibited a lower distribution of SCWT compared with that of the normal case. However, the air supply and indoor temperature distributions as well as the indoor set-point temperature unmet hours remained similar (Figures 9 and 10).  
The evaluation of indoor thermal comfort following the correction of faults in the SCWT sensor indicated that the impact of faults on indoor thermal comfort varied based on the fault occurrence frequency and offset. Faults with fixed or random offsets were likely to cause variations in their impact on thermal comfort. Additionally, faults with fixed offsets or those that changed gradually over time, especially with negative offsets, were found to adversely affect indoor thermal comfort, as evidenced by the increased indoor set-point temperature unmet hours (Table 6).  
Figure 10: Indoor set-point temperature unmet hours with various fault types.