Power quality issue:. Dips over 40 in month

We started out having issues with a outside breaker tripping the inside lights and plugs for front bedrooms of our house. We had an inspector come out for our warranty and he said it was gfci not afci well electricians under our builders warranty came out and they are afci and gfci breaker small through breaker panel … So we think tripped breaker is from overload because they put so much on that breaker

I went to sense and noticed the sensenlabs area and saw we were having voltage dips… Leg a and leg b both drop as low as 40v but the voltage stays close of both legs even with voltage drop that low.

Did you noticed any other signs of this issue around your home?:

When ac comes on we do get flicker of light nothing huge … And same on that breaker I spoke about above light gets a bit brighter

Screenshots from Sense Lab
I attached voltage dips report from both August and December January. Strange thing is we didn’t have any untul December

We have had electricians out and power company boone is real investigative but can’t find issue.

Any help is appreciated.

A couple of other things might be involved:

– there could be a poor building panel ground to earth ground, which is insufficiently sized for the additional loading.

– circuit wiring undersized for the length of the runs and the loads. Besides the heat/fire potential of under-sized wires, they can also exacerbate transient spikes.

– neighborhood transient loads. Unfortunately, it’s really difficult to find & show correlations with a neighbor’s transient loads. But ‘listen’ if you notice lights flickering…


We had power company out again today and he tested everything at panel and main pulled meter off checked the green boxes in front of our house, then went to transformer and checked that and pole.

He checked sense to his equipment and it all matched. He said with voltage drops were getting everything should shut down.

In a different direction of thinking … maybe the CT’s are getting random mechanical vibration, which will disturb their readings. I’ve seen pictures where some people have taped their CT’s in place so they stay in a stable position relative to the wires they are measuring.

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My husband said they are secure and we didn’t get dips when breaker box was opened up by both electricians and power company

It happened again this morning…I was :sleeping: sleeping… Power co has quality monitor in meter… They installed yesterday


Now we are having spikes. Electric company has been out they say must be inside house. Electricians day it’s power company

Any assistance is appreciated

I’ve seen this mentioned a few times on this forum with respect to the voltage monitoring feature. The service entrance neutral-ground bond, or any safety grounding issue for that matter, will not have an effect on the measured voltage levels on the main power legs (what Sense is monitoring as part of this feature). Unless there is a wiring fault, the safety grounding path does not carry any current at all. If current is flowing on the ground, or through the N-G bond, there is a hazardous condition that should be cleared by a breaker tripping. Another cause for current on that connection is a failed/loose utility neutral connection, which Sense should pick up with a different Labs feature. But hunting for issues throughout a home’s grounding system while expecting to fix an issue with the Sense power quality readings is going to be a wild goose chase.

Can you clarify? Did the power company’s voltage monitor show that the incoming service is clean? If so, have you taken that data to the electrical contractor and asked them to take another stab at it now that the utility equipment has been verified? Did you compare the data from the power company’s readings to the Sense readings to be sure the issue was occurring while the power company was gathering its data?

Wow. That’s a lot of problems in the power quality here.
It’s clearly voltage dips issue from the utility. Sense labs have been shwoing all the accurate information for me since day 1. Also all such events for me were compared to my APC (schneider Electric) UPS BN1100M2 set to medium sensitivity which matched all such events flagged by Sense. However sense was able to capture all of these dips and spike while UPS didn’t register all of them since it may have been filtered due to transient nature of such dips.

  1. two times I personally witnessed light flickering, I instantly noticed one of my UPS kicked in. And after 10 hours or so, I was able to see those voltage dips of 80V on both legs which matched exact time stamp for the ups kicking in and those light flickering.

I wouldn’t doubt sense labs information at all. They are simply getting the voltage nput directly from your panel which is your utility company power. There cannot be any other explanation to this issue other than Utility power quality issue. Unless you live next to the Industrial area where they turn on huge induction motor loads every now and then which could cause such dips in voltage. Regardless of dips, your utility should be responsible for the poor power quality.

Sense captures those voltage values pretty precisely using very good sample rates and thus it cannot be challenged in my honest opinion…

You should push back on Utility guys to provide clarification on the power quality issue.

I would also recommend getting a small UPS for router or something, and set the sensitivity to medium. APC 1100VA or 1500VA etc. Model BN1100M2 or BN1500M2 to verify such issues. That way you can prove utility guys about events captured on both sense labs and UPS.

Loose connections or other degradations in the service entrance equipment behind the meter can also cause these issues (though less commonly) and those are not the utility’s responsibility.


Absolutely, as notes suggest on the sense labs view.
That’s why UPS could help determine if there are really power quality issue or not. Very straight forward solution and won’t have to rely on either electrician to rule out. You yourself can show these finding to the utility guy.

Update… I had power company out again the lineman that was out before recognized our address and took our call… He gave me his email and I sent him dip reports . The voltage spike was confirmed as something that went haywire at power company.
From lineman:

The dips not sure if this will rectify situation but lineman emailed me back this morning.

"The dispatcher called me this morning. He said the tap changer in the substation has been repaired."


I’m not sure what a UPS has to do with anything here. There is little reason to dispute the Sense power quality data.

At any rate, it sounds like the OP has a good lead on a solution here.


Ups data can be used a basis to back sense data if utility guy ask for further confirmation.
Along with sense, specially for the voltage drop/power quality issue, ups will help determine problem if set to work under sensitive option. So that it is in line with sense labs data.

If it helps the lineman loves the sense and is going to purchase one… everytime he has come out and we have worked together one this … The sense has been dead on… He loves it… It’s an awesome resource… This device has helped us now in our 2nd home. The first time we had issues with a poorly installed a/c and sense showed it and we figured out we had a neutral issue on that house, too… Sense for the win! Hoping this update and repair will take care of drops too not just the one voltage spike we got.


Thanks for sharing this story, @4everglutenfree !
Did you say the name of your power company was Boone?

No it’s duke

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