False Readings Seemingly Caused By High Amp Load

[weirdheater]

I have an electric boiler that heats water for hot water radiators, which is on a 150 Amp circuit. The unit is rated to draw up to 100 Amps at peak operation. I have two 50A CTs on each leg of that double-pole circuit.

I’ve noticed that, when the boiler is heating, two other circuits register power draw that shouldn’t be there. One of those circuits is for my office where I have unplugged everything AND turned off the breaker, and it still registers about 9 W when the boiler is heating. Another is for my fridge, which I haven’t tried shutting off at the breaker yet, but that circuit registers around 13 W exactly when the boiler is running and the fridge is doing nothing. Both circuits stop reading the unexplained power draw when the boiler shuts off.

Both of these circuits are single-pole and on the same phase and same side of the panel, for what it’s worth. I have one other monitored circuit on the same side of the panel and same phase that isn’t showing any strange readings.

I have also noticed that the balance of power from unmonitored circuits is higher than it should be when the boiler is operating. When the boiler turns on, the “Balance” shows about 4.5 kW higher than it did the minute previously, even though nothing else in the system has changed. It drops back to an expected range when the boiler shuts off.

I have solar, but I’m observing all this when the sun is down.

What could be causing these strange readings? Could it be the magnetic field generated by the boiler circuit’s high current is strong enough to cause nearby CT’s to show a false reading? That doesn’t explain the extra power draw shown by “balance” unless the field is strong enough to influence the 200A CTs also. I doubt that!

Could it have something to do with reactive power from the circulator pump that is powered & switched by the boiler control board?

If nobody knows the cause or a fix, I’m open to ideas for how to test and troubleshoot the problem.

[weirdheater]

Update…

I’ve been paying close attention to what happens when my boiler runs, and I’ve gathered some more relevant data points.

First, I did shut off the circuit with the fridge on it, and it still registers 13-14 Watts when the boiler is drawing maximum power (around 9.2 kW). When one of the boiler’s heating elements turns off, the power reading on the shut-off fridge circuit goes down by about 2 Watts per element. Weirdly, at least once the reading went to zero when I re-energized the circuit with no change in the boiler’s power draw (all 4 heating elements energized). And then it started registering a very noisy signal spiking from 0 – 5 Watts when one of the elements turned off.

Another strange thing is that the CT for the fridge circuit registers about 5 Watts when that circuit is shut off and my electric kettle (totally separate circuit) is turned on!

I also noticed another circuit (some outlets and lights) showing about 7 Watts when it’s turned off at the breaker and the boiler is on. It’s also on the same phase as the other circuits that are showing activity when they shouldn’t be.

So that’s a total of 3 circuits that show power consumption, even when shut off, while the boiler is running. The unusual power consumption fluctuates with the power consumption of the boiler as elements turn off and on.

Finally, it’s worth noting that the voltage across all circuits including the mains dips by about 5V whenever the boiler is running. I guess because it’s such a huge load. Could that be causing the Emporia device to read things improperly?

I’m stumped. Any ideas what could be happening?

[emporiacs]

Hi!

We have some insights for you that should help!

The 50A sensors reach saturation at 75 amps but will decrease in accuracy as the current approaches this saturation limit. If you are seeing inaccurate readings from the sensors while the unit is drawing more than 50A could be the cause a reading accuracy issue.

Please contact support directly and we can look at the raw data and see if over-amperage is causing either of these issues. We’ve appraised the team of your update below as well. Please just reference your message with a link to this thread for reference.

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