Instruction manual
www.DaikinApplied.com 43 OM 751-4
troubleshootInG temperature sensors
The UVC is congured to use passive positive temperature coefcient (PTC) sensor
whose resistance increases with increasing temperature. The element has a reference
resistance of 1035 ohms at 77°F (25°C). Each element is calibrated according to the
tables shown.
Use the following procedure to troubleshoot a suspect sensor.
1. Disconnect both sensor leads from the UVC.
2. Using some other calibrated temperature sensing device, take a temperature
reading at the sensor location.
3. Use the temperature reading from Step 2 to determine the expected sensor
resistance from Table 23 on page 43.
4. Using a calibrated ohmmeter, measure the actual resistance across the two sensor
leads.
5. Compare the expected resistance to the actual resistance.
6. If the actual resistance value deviates substantially (more than 10%) from the
expected resistance, replace the sensor.
Table 23: Temperature versus resistance
°F (°C) Resistance in ohms °F (°C) Resistance in ohms
–40 (–40) 613 113 (45) 1195
–31 (–35) 640 122 (50) 1237
–22 (–30) 668 131 (55) 1279
–13 (–25) 697 140 (60) 1323
–4 (–20) 727 149 (65) 1368
5 (–15) 758 158 (70) 1413
14 (–10) 789 167 (75) 1459
23 (–5) 822 176 (80) 1506
32 (0) 855 185 (85) 1554
41 (5) 889 194 (90) 1602
50 (10) 924 203 (95) 1652
59 (15) 960 212 (100) 1702
68 (20) 997 221 (105) 1753
77 (25) 1035 230 (110) 1804
86 (30) 1074 239 (115) 1856
95 (35) 1113 248 (120) 1908
104 (40) 1153