Troubleshooting Temperature Sensors - Daikin MicroTech II Installation And Maintenance Manual

When the MCB finishes downloading to the keypad/display it
sends a "download complete" message to the keypad/display.
When this message is received, the LCD shows the "main"
rooftop application menu screen.
Note – A NO COMM indication on the Status line during the
initialization period does not necessarily indicate a
problem. A communication problem is indicated if the
LCD "hangs," i.e., it does not proceed to show the "main"
rooftop application menu screen.
If aaaa= IRAM, bbbb= XRAM and/or ccc= ROM, replace the
keypad/display.
Note – The keypad/display can be connected to the MCB while
power is on. The normal elapsed time for the "main"
rooftop menu screen to appear in the LCD upon
initializing is approximately 60 seconds.

Troubleshooting Temperature Sensors

The MicroTech II temperature sensor consists of a positive
temperature coefficient (PTC) silicon sensing element. The
resistance of this sensor 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 graphs
shown in Figure 29 (°F) and Figure 30 on page 64 (°C).
Tabulated resistance vs. temperature data is shown in Table 25.
Use the following procedure to troubleshoot a suspect sensor.
1
Disconnect the sensor from the MCB.
2
Take a temperature reading at the sensor location. Be sure
to allow the thermometer to stabilize before taking the
reading.
3 Use the temperature reading from Step 2 to determine the
expected sensor resistance from Table 25.
4 Using an 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 found in Table 25,
replace the sensor.
Daikin IM 696-4
Table 25: MicroTech II temperature sensor—temperature
vs. resistance chart
Temperature °F (°C)
-40 (-40)
-31 (-35)
-22 (-30)
-13 (-25)
-4 (-20)
5 (-15)
14 (-10)
23 (-5)
32 (0)
41 (5)
50 (10)
59 (15)
68 (20)
77 (25)
86 (30)
95 (35)
104 (40)
113 (45)
122 (50)
131(55)
140 (60)
149 (65)
158 (70)
167 (75)
176 (80)
185 (85)
194 (90)
203 (95)
212 (100)
221(105)
230(110)
239 (115)
248 (120)
Test Procedures
Resistance in ohms
613
640
668
697
727
758
789
822
855
889
924
960
997
1035
1074
1113
1153
1195
1237
1279
1323
1368
1413
1459
1506
1554
1602
1652
1702
1753
1804
1856
1908
63