Measuring one of 3 phase using a single CT

For a project I am trying to show availability of washing machines, located downstairs in my apartment building. Using the openenergymonitor, I would like to measure if there is electricity flowing to the washing machine. I am not interested in the actual power, just seeing if it is on or off.

The machines use 3 phase power, but to minimize the investment, I would like to use just one CT per washing machine. I am having trouble figuring out which Arduino code I have to use. I have tried single phase code, but, as expected, did not get a reading. All the code I can find use at least 3 CT’s to find actual power.

Can someone explain what I should change to existing code, or point me to the right github, so I can continue with this project?

Many thanks for your help!

If all you want is to measure the current flowing in the supply to the machine, you need to find which phase it uses most of the time. It is quite possible that the water heater is three phases but the controls, and possibly the motor also, is single phase.

The most basic sketch for single phase: should work for what you want.

How did you install your CT? See Home | OpenEnergyMonitor