[Project] Fault Detection: Floating Neutral is an algorithm that identifies homes with irregular Power Quality. Floating Neutral identifies homes that dip equal to or greater than 2V at the beginning of the start-up of a single-leg device with an inverse increase of voltage on the other leg.
If you’ve received a notification in the Sense app about a Floating Neutral issue, we’d like you to share details here in the Sense Labs community. Please answer the below questions surrounding your issue so we can continue to help users in the future with this issue.
Required information to include:
Did Sense detect a floating neutral in your home?
Did you receive a timeline notification or email from Sense OR discover it yourself in-app?
Did you notice any signs or irregularities prior to the issue being resolved?
E.g. Lights dimming or flickering
How soon after detection did an electrician come inspect the issue?
Was the issue resolved by an electrician or your utility?
E.g. electrician confirmed a floating neutral and replaced
What was the official diagnosis from an electrician or your utility?
Floating Neutral Resources
Below is more information about neutral issues that may be detected by Fault Detection: Floating Neutral. If you have suggestions for additional resources to add to this list, please reach out to @JustinAtSense.
Justin! An excellent and simple solution. You have some smart cookies working there. One note is that the “start-up of a single leg device” needs to be an event that does not require a previous device detection to qualify as “a single leg device”. A simple turn-on of any 120V device, known or unknown, should qualify in order to make floating neutral detection as reliable as possible.
The next question would be, since no one other than Flash can get to the main breaker quick enough to shut off the power before stuff gets fried - what exactly should the home owner do to protect himself from the threat of up to 240V applied to half of the circuit breakers? A high capacity whole-house surge protector connected to the main breaker won’t work because their MOV’s engage at higher voltages than many appliances can tolerate for the relatively long periods of time involved with an open or loose neutral. They would have too much leakage if they spec’d them to clamp low enough to help with neutral issues. They are by design a good tool to swat down very brief, very high voltage transients typical of lightning strikes.
The next question would be, since no one other than Flash can get to the main breaker quick enough to shut off the power before stuff gets fried - what exactly should the home owner do to protect himself from the threat of up to 240V applied to half of the circuit breakers? A high capacity whole-house surge protector connected to the main breaker won’t work because their MOV’s engage at higher voltages than many appliances can tolerate for the relatively long periods of time involved with an open or loose neutral. They would have too much leakage if they spec’d them to clamp low enough to help with neutral issues. They are by design a good tool to swat down very brief, very high voltage lightning-type transients.
I’m not aware of any off the shelf device that is made for this application. The controller for my standby generator has an option to immediately drop the load from the mains if the voltage on either leg is out of the specified limits, but this generator controller is made for industrial applications. One could put together a protection scheme for this using some monitoring relays and a big contactor, or a shunt trip circuit breaker, but the cost would be well into the thousands and would end up being difficult to physically install alongside typical residential service equipment.
I think for the typical homeowner, the most effective way to protect against floating neutrals is to proactively have your electrician inspect your service entrance equipment and replace/repair anything that looks loose or damaged. The electrician may also be able to look over the nearby utility equipment and suggest that they make repairs to anything that looks fishy.
Ultimately, this is the goal. A lot of folks are unaware of potential neutral issues, and we hope this can serve as a tool to help increase awareness for homeowners.
It’s also worth pointing out that in most cases, voltage imbalance and fire hazards from a floating neutral develop slowly over time as connections loosen and corrode. The sense monitoring feature will allow homeowners to catch and correct this problem before it becomes a hazard. Now, that won’t always be the case, as excavations and wiring mistakes can also cause an open neutral, but I’d say that the vast majority develop slowly over time.
That’s a great point @pswired and it begs the question: can the Floating Neutral fault detection lab probe the data deeply enough that in some cases the slow neutral degradation can be identified and “failure” preempted.
This reminds me of solar analysis to demonstrate panel degradation vs fixable weather effects like snow and dust. Hope Solar Labs are coming!
@winfield100 Do you have a tankless water heater? I ask because these heaters can draw so much power that they can affect the voltage being delivered elsewhere in your home while running, which can cause lights to flicker. I’ve seen suggestions from folks to upgrade lightbulbs in this scenario, and if that doesn’t work, consulting an electrician might be the best move.
Upon further looking, we realized the flickering lights when the tankless water heater goes on, are LED’s on a dimmer switch.
It appears to be the dimmer
Thank you for your kind response
There are still many “Aluminum Wired” homes and an indication to “re-torque” would save lives. My sister in law was having an AC issue and I found a breaker almost burned through due to a high resistance connection! Changed the breaker and found other connections very loose!
Since you mentioned torque, people should also know this: as part of the NEC since like 2017, basically every screw-terminated electrical connection in every building should be torqued down with a torque screwdriver. For outlets, the lower end ones take something like 12 inch pounds, the higher 14-18. For breakers, they start at 36. It’s way more torque than you think it is.
And yet, very very very few electricians do it. There’s no enforcement.
You can get a cheap torque screwdriver on Amazon for like $40. It’s honestly the only way to guarantee a consistently safe electrical connection. Anytime you have an electrician in the house to do work, if they don’t have one, provide them with yours, and make sure they use it! Your comment was about aluminum wiring, where torque is even more critical than copper wiring, but it definitely does matter for copper wiring. Not just for making sure the wires are neither loose nor crushed, but at the right torque value, you do actually get a lower resistance connection!
Thank you for sharing this information, @test35965. NEC-2017 was adopted effective July 1, 2021 in the state where I live. That version added this requirement: “where a tightening torque is indicated as a numeric value on equipment or in installation instructions provided by the manufacturer, a calibrated torque tool shall be used to achieve the indicated torque value, unless the equipment manufacturer has provided installation instructions for an alternative method of achieving the required torque.” NEC 2017 110.14(D)
You can bet they’re seeing failures in the field when people back-screw-clamp wire if they’re going out of their way to change language like that. The inspectapedia mod said it probably had to do with Aronstein’s forensic work. I suspect that wiring method has way more trouble with conductors pulling out.
One more thing about resistance: I saw a video on YouTube by some UK electricians. They tested torquing stranded wire into terminal blocks. There was a clear drop in resistance for each increment!
