You are checking the supply chilled water temperature thermistor probe on a highpressure hermetic centrifugal chiller. Using the illustrated chart, what statement is true if the supply water temperature is verified 45°F with a digital thermometer? Illustration GS-RA-48
• Thermistor temperature vs. resistance/voltage chart – which column gives you voltage and which gives you resistance at 45°F? • Difference between checking a thermistor in-circuit (connected) vs isolated (out of circuit). • Why you need control power ON to measure a voltage drop across a sensor.
• From the chart, determine the voltage drop and resistance values that correspond to a thermistor temperature of 45°F. Which number matches each unit? • Think about what you can actually measure if the thermistor is isolated from the circuit. With no current flowing, can there be a voltage drop? • Among the choices, which ones correctly pair: power condition, thermistor connection (in or out of circuit), and the expected voltage value from the chart?
• Verify at 45°F the chart’s voltage drop in volts and resistance in ohms; don’t mix them up. • Check which options incorrectly use the resistance value as if it were a voltage. • Confirm that a voltage drop requires both control power ON and the thermistor connected into the circuit so current can flow.
No comments yet
Be the first to share your thoughts!