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I was measuring current flow in some 220VAC/60Hz household circuits in a USA split-phase load center using a UNI-T UT203 clamp meter. The meter yielded a surprising result for an electric induction range that was powered OFF, and I'm trying to determine if the meter is wrong or I'm just missing something:

I took the following measurements:

(CB = Circuit Breaker to range circuit)

  1. Main feeder with range OFF and range CB ON: 5.51A
  2. Range circuit with range OFF and range CB ON: 3.09A
  3. Range circuit with range CB off: 0.07A
  4. Main feeder with range CB off: 3.99A
  5. Range circuit with range ON (1 element): 6.7A
  6. Main feeder with range ON (1 element): 9.4A

I was very surprised to see the range drawing 3A when OFF. This equates to approximately 660W parasitic load, and would be a huge problem and waste of energy. However, the unit is not hot, so where would this wasted energy be going? This leads me to not believe these values.

Also, the home also has a Sense electrical monitor on the incoming feeders, which contradicts the clamp meter's output:

  • Sense doesn't show any change in wattage with range OFF and its CB on or off.
  • Sense shows wattage increase when range is ON and heating: approx 1.4kW increase.

Why is the clamp meter showing 3A draw by the range circuit when the range is off? Is this accurate, or is the Sense accurate? Is my meter useless garbage?

I'm being very careful to ensure the meter's clamp is fully closed around a single conductor when measuring the various circuits. And yes, the meter is in AC mode on the 40A range selector.

Thank you for any pointers.

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  • \$\begingroup\$ Strange- Could it be reactive current? There'd be no power dissipation in that case. \$\endgroup\$
    – John D
    Commented Jan 14 at 17:16
  • \$\begingroup\$ CB = center burner??? \$\endgroup\$
    – Fred
    Commented Jan 14 at 17:21
  • \$\begingroup\$ @JohnD could this be coming from another circuit (HVAC system)? That's the only other thing running. Range is completely powered off (soft switch) so...? \$\endgroup\$
    – Ryan Griggs
    Commented Jan 14 at 17:21
  • \$\begingroup\$ @Fred CB = Circuit Breaker (edited question) \$\endgroup\$
    – Ryan Griggs
    Commented Jan 14 at 17:22
  • \$\begingroup\$ Sure, if there's another circuit that's powered it could be coming from there. The only way it could be reactive current would be if there was a bank of AC capacitors across the line at the input to the stove which I think is unlikely. \$\endgroup\$
    – John D
    Commented Jan 14 at 17:54

1 Answer 1

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The first thing you need to do is check the manual. There is a 'zero' button and it neds to be calibrated with the methods described in the manual.

enter image description here Source: UNI-T UT203 clamp meter manual

If it's not that if you had some strong magnetic fields locally from other equiptment that could be causing a problem. I doubt it's that. Another thing is it should read zero if not clamped to a wire If you calibrate the meter and it still is erroneously reporting current, it's probably broken.

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  • \$\begingroup\$ Thanks. The meter reads zero when not in contact with wires. Also, I'm reading AC current measurements, not DC. \$\endgroup\$
    – Ryan Griggs
    Commented Jan 15 at 14:02

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