CT Clamp Specs

Does anyone by chance have the specs on the minimum flow rate that the Main and Flex CTs can detect? One of my dedicated circuits being monitored with the Flex sensor shows now usage when I know that the Dryer it is monitoring draws a very minimal amount of power. If it is anything like my washer that is being monitored by a TP-Link Kasa KP125, it should be drawing just under or around 1W.

Does the Device listing for your Dryer show a number for the power usage right now ? I don’t know the specs on the combination of the CTs plus the measuring circuitry inside the monitor, but I’m fairly certain it will track down to just a few Watts. I have a subpanel with 5 floor heating elements and 5 thermostats on it. Nuvent disclosed that each thermostat uses under 2W when not heating. The subpanel is monitored by a DCM CT and I can see a Standby value of 7W for all 5 when none of heating elements are energized.

Just like with the KP125, you can customize the power threshold for labeling the usage as Standby vs On.

I have a CT on a circuit for my garage, ‘Always On’ shows an always on of 3w for the 2 motion sensors on the circuit.
My other CT is on my pool pump circuit when not in use the only draw is a Sonoff switch that doesn’t report an always on value.
I imagine Sense rounds down.

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You reminded me of one more detail - I’m guessing DCMs are like Kasa smartplugs - when power goes below 0.5W, Sense will consider the device OFF and won’t show bubble and will grey out in devices list. So @ranger73, expect the device to Dryer to show up as On (or Standby if configured) unless usage drops below 1/2 Watt.

You also reminded me of something.

CT’s are a bit different than Kasa in that CT’s minimum standby to ‘On’ is 3w. Kasa has no minimum.
That being said, you will not see a bubble or device history for CT usage under 3w.

I have Kasa plugs that show a standby wattage of 1w and ‘Always On Devices’ with 1w.

So I’d say for all intensive purposes it’s safe to assume CT’s can only go down to 3w.

I imagine the reasoning is due electromagnetic fields inside electrical panels (where the ct’s are located) could cause a false reading at that low of wattage. Similar in a way how non contact voltage testers works.



Thanks everyone for your replies. This all makes sense. I know CT clamps are not created equal and was trying to determine if I should be seeing anything at all below a specific threshold. I have a hand meter that I was able to determine there is a very small draw on the circuit, but needed to verify if Sense would detect that load. It is not a big deal, just wanting to understand the equipment and it’s limits.