Heating, Ventilation, and Air Conditioning (HVAC ) Electrical Practice Test

Technician #1 claims that an OPEN transformer coil is indicated by a reading of infinity on an analog ohmmeter. Technician #2 states that a SHORTED transformer coil is indicated by a reading of infinity. Who is correct?

1. Technician #1 only

2. Technician #2 only

3. Both technicians are correct

4. Neither technician is correct

The correct answer is: Technician #2 only

To understand the correct answer, it's important to clarify the concepts related to transformer coils and how they are tested with an ohmmeter. A reading of infinity on an analog ohmmeter indicates an open circuit. In the context of a transformer coil, when Technician #1 states that an open transformer coil is indicated by a reading of infinity, this aligns with electrical principles. An open coil means that there is a break somewhere in the winding, preventing current from flowing, which results in an infinite resistance reading. On the other hand, Technician #2's claim that a shorted transformer coil is indicated by a reading of infinity is incorrect. A shorted coil implies that the windings have connected improperly or that there is an internal connection causing a low resistance, which would show a value significantly lower than infinity, often close to zero. Thus, a reading of infinity would not indicate a shorted condition, but rather indicate that the coil is open. Therefore, Technician #1 is correct about the open coil indicating infinity, while Technician #2 is not correct in his assertion regarding short circuits.