Iotawatt switching pos/neg values without solar

[jll316]

Bob,

We have been experiencing (already for some time) certain power values changing from positive to negative, without there being solar or changing the direction of the CT sensors. It has been quite unpredictable. We work with 3-phase split systems (127 V).

What is strange is that it does it when certain appliances turn on/off, and it doesn’t do it with all ports in the sensor. It keeps the stand-by consumption, but that specific appliance (or combination of appliances) is integrated to the overall signal in the opposite sign. The graph here has an example of what we are talking about (here the triggering example is a clothes dryer).

I would imagine this has to do with power factors and the circuit changing from capacitive into inductive? We plotted power factors and these seem to be negative and positive, but should always be between 0 and positive 1.

If you can point us to where we can coerce power factors into absolute values or help us detect the root of the problem, we would be very thankful.

[overeasy]

I don’t have enough information to understand your problem.

First, I don’t know what a three-phase split system is. Can you show a line diagram of that? Can you post your inputs setup?

Can you plot this problem using Graph+ showing both the affected value and what you believe to be appliances causing this problem? Also be sure to show the legend and axis of the plot.

When someone talks about three-phase and negative values without solar, it usually means the setup is wrong. Are you using derived or direct reference?

[jll316]

Thanks Bob,

Sorry about the incorrect term. This is a 3-phase system with 120 deg between phases at 127 volts each phase relative to the neutral.

Here is the Graph+ plot

And we are using a direct reference.

Thank you very much for your help.

[frogmore]

I am going to agree with Bob on this one. You don’t have your references correct. Either that , or you have some VERY unusual loads. PF should be close to 1 for most loads. I have a new blower motor for the furnace that goes down to 0.62 or so when it is on low. The furnace itself goes down to 0.3-0.4, but it is only using 10W or so at that point.

You need to go through the instructions on setting references for 3 phase systems again. There are many more ways to get it wrong than there are to get it right.

[overeasy]

Just to be clear, you are saying that you have three VTs? Can you show your inputs setup and also a plot of the input showing the problem with a smaller time window like an hour?

[jll316]

Hi Bob,

In this case we had 2 VTs (we sensed inputs coming from only 2 phases), but the problem occurs with 3 phases as well, again with one VT per phase.

Here is a photo of the inputs:

The status (not long after the Iotawatt was installed):

And here are photos of Graph+ with smaller windows: