BlueSea Monitors Holding Tank Problem

[Neo]

We finally calibrated the holding tank (ultrasonic gauge connected to BlueSea monitor VSM422).

So we know that the tank is empty, and the BlueSea monitor indicates that the tank is empty. Check.

The high alarm is set to 80% and the low alarm is off. Check.

Problem: When we turn off power to the "instruments" at the DC panel, the holding tank goes from 0% to 100% and the alarm sounds. When we turn the instruments back on, the value goes to 0% and the alarm stops.

I am not sure if the instruments were powered when I did the calibration.

What should I be looking for? The system was installed by the PO.

[GordMay]

"... The Blue Sea Systems ultrasonic sender requires an external power source.
When power to the sender is lost, the VSM 422 will read the tank as full, and
may trigger the tank’s high level alarm...”
Page 9 ➥ http://assets.bluesea.com/files/reso.../990470210.pdf

[Neo]

Thanks, Gord.

I guess we have to bypass the panel and wire the ultrasonic sensor directly to the house battery.

I'll be sure to connect the ultrasonic sensor's negative wire to the panel side of the shunt so that the draw from the sensor registers on the BlueSea monitor.

I assume the draw from the sensor would be minimal.

The OP seems to have wired the shunt incorrectly as well. The BlueSea shows negative amps when our solar is charging the house battery. According to the manual it needs to be show positive amps for the SOC function to work.