"signals" in Sense app

Two weeks post Sense :slight_smile:

I was playing around in the app. In the Settings/home section there is a section called “signals”

Within this there is watts and voltage

For mine the two watts are not the same vs. volts being very close.

What are these? Why are watts not the same? Should I be concerned install didn’t go well.

Thanks

The “signals” display shows the voltage, current and power flowing to each of the two legs of power distribution in your house. Homes in the US use split phase power delivery:


That means you have two separate “legs” delivering 120V power from the transformer outside your house. Typically electricians try to balance loads inside the house so that current and power are comparable, but that really depends on what loads are on and off inside your house at any one time - both current and power can be very different between the legs. Voltage is controlled by your utility and must be within a fairly tight tolerance. Current and power vary depending on the loads.

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Thanks, that is exactly what I thought it was.

Is it normal/ok for them not to be the same

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They will usually be fairly different and that is normal.

“Balancing” the legs is ideal because it splits the load on the incoming supply from the Utility (or your solar supply) and the wires.

For most dual-phase (208/240V) devices the device itself will be using the supply in a perfectly balanced fashion between the phases. In some cases a 240V device can use ONE of the phases internally … e.g. a 120V fan in an otherwise-240V device like an AC unit. This leads to imbalance.

Imbalance also comes in the form of more 120V being used on one phase (leg) that the other. This is normally what you are seeing with the different wattages on each leg.

Unless you have a badly put together panel with, say, too many breakers on one phase, or lots of devices plugged into, by chance, one phase then generally houses are close to balanced (enough) that the imbalance makes no difference at the Utility level.

As a general rule, the more devices you have plugged in the more the power converges toward balanced. At the scale of the grid you can imagine things get very close on each phase.

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Actually,

What started this whole thing was an electrical audit. My panel was HORRENDOUS. Looked like spaghetti. I have some before and after pics I will have to share.

Prior to this both 240s were on one side. He put them onto both sides (phase). I think he did a great job. The pics will show. Let me get them posted.

As I type this i’m running AC dyer dishwasher, washing machine. I’m pulling 8000 watts. Of those two mains, one is 4200 the other 3600 not too far off. I have seen them closer and further apart.

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Pics

image

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Yowzers. Nice cleanup.

Not to burst your balloon but the shifting of the 2-phase breaker doesn’t modify the load balance. Meaning: It was probably fine before other than old breakers and dodgy whatnots.

In your existing (new) setup the top left 2-phase breaker is on A (black wire usually) + B (red wire usually) phases (vertically down the left side). So the next breaker in your old config would have also been A + B. The phases alternate down the vertical. It’s not the case that the left side = A and the right side = B.

That neutral bar arrangement is new to me though I suppose “normal” … pretty tight in there.

Looking closer I see you have a nominal 100A (125?) panel and wires … like me you might want to set some upper-limit wattage notifications in Goals as a kind of pseudo-overcurrent alarm. I have a couple set to around 9kW as detailed here.

On another note and by way of FYI: my panel is actually 2 of 3 phases supplied to the building. What this means is that my supply phases are actually at 120deg to one-another versus the usual 180deg so the effective voltage I have is 208 and not 240V. Sense deals fine with this up to a point but Support is investigating calibration issues I have with the solar CTs (that I am using for individual device monitoring). I suspect, though I’m not sure, that this also creates a challenge for detection … in the same way that if you move around breakers/circuits and switch phases after Sense has detected a device you may well lose that detection because the detection is generally “locked in” to the current phase … meaning: just seeing a power waveform and looking at signals for more realtime info is not showing you all of what Sense is monitoring.

One thing about “imbalances” between legs.
Even if each side had a difference if thousands of watts, it’s nit a problem and the cost of electricity down not change.