I have 2 pumps being controlled by a PIC, 1 has a 1/2 hp motor, the other has a 2.5hp motor. They can be 110v or 220v 50 or 60hz, it depends on the installation but the voltage or frequency does not change the results.

Using a Fluke meter with an Amp Clamp, I read the 1/2HP as drawing 3.2 amps, and the 2.5hp motor is drawing 18.5 amps. These readings always closely match the FLA number on the motors faceplate.

So it seems that if I add the 2 numbers together, the total current draw should be 3.2 + 18.5 = 21.7 amps total current.

But when I put the amp clamp on the wire feeding both pumps, I always get a reading of around 20.7. 1 amp less than the 2 numbers added together.

Doesn't matter what voltage, frequency, single phase or 3-phase, the total is always less than the 2 combined.

I am also reading the currents with the PIC, and it comes up with the exact same numbers.
Of course the customer says that it's WRONG.

Please help keep my barber in business.
There's gotta to be a reason somewhere.