Sense Now Tracks Power Quality in Homes and Detects Floating Neutrals

The Sense monitor uses high resolution voltage data and advanced machine learning techniques to analyze energy patterns in the home in real time. With the Floating Neutral project, Sense proactively diagnoses problems in the home that might otherwise go undetected and alerts homeowners to take action. For Sense’s utility partners, hearing from customers with insights about floating neutrals helps the utility address problems more efficiently and reduces the risk of electrical fires.

Since introducing these projects, many Sense customers have taken action to remedy dangerous electrical situations they discovered in the Sense app. One customer had seen his lights flickering but didn’t realize it was a serious issue until he saw hundreds of power dips in his home’s Power Quality graph. Another Sense customer discovered a partial break in a neutral wire after seeing his irregular voltage patterns. Yet another customer was alerted to a floating neutral in the Sense app and immediately contacted his utility company to get it fixed.

Sense Labs is Sense’s invention space where the company previews features under development that can make smart homes more insightful and less wasteful than they are today. In the Labs, Sense shares projects that push the boundaries of smart home innovation, moving closer to the company’s vision of a future when intelligence is built into the home itself. With intelligence about electricity and other resources built in, a new generation of smarter homes can discover problems, lower carbon emissions in coordination with the utility grid, reduce costs, and automate maintenance.

The Power Quality Project

The Power Quality project continuously tracks the voltage coming into the home and identifies dips and spikes. Most homes in North America have split-phase 120/240V electric service. In a split-phase 120/240V electric panel, each leg in the home’s electrical service panel should sustain a voltage of around 120V. This project identifies fluctuations outside of a normal range.

When voltage drops 10% below the normal threshold, it’s flagged as a dip. When it rises 10% above the normal range, it’s flagged as a spike. Brief voltage dips and spikes can be harmless. However, frequent dips and spikes may indicate an issue with the power feed from the utility or the wiring inside the home. The user is alerted in the Sense app and can see how frequently the fluctuations took place, when, and how their home compares to most other Sense users.

The Floating Neutral Project

A “floating” neutral occurs when the connection to the home’s neutral wire breaks or becomes loose. When this happens, the voltage on one power leg increases while voltage on the other decreases, so some electrical devices receive increased voltage, while others receive less. This condition can cause damage to appliances and potentially pose a fire or shock hazard.

In a typical U.S. home (Sense is also available in Canada), 240V electricity flows into the electrical panel via two power legs from a utility transformer. The phases are inverses of each other, with each carrying 120V relative to a third neutral wire. When the neutral wire breaks or becomes loose, the neutral can “float.” This can be a problem with the utility wiring or wiring in the electrical panel in the home.

The difference between the phases remains 240V, but the voltage on each leg is out of balance without the neutral. The lights in the home might start flickering or an outlet could be energized with up to the full 240V, which can damage devices and pose a shock or fire hazard.

Sense detects a floating neutral by seeing when the voltage on the two phases drifts away from each other. The larger the load imbalance, the more serious the issue. Sense users receive an alert in the Sense app letting them know a floating neutral may have occurred in their home.

Examples of how Sense works:

• Sense alerted Tom B. about the danger of a floating neutral in his home. Tom had seen flickering lights in his home but hadn’t pinpointed the cause. He contacted his utility who fixed a poorly connected neutral that was spliced to the main feeder wire near the pole.
• Curtis K., a Sense user in Raleigh, North Carolina, opened the Sense Labs project and saw 74 dips or spikes in his home’s power in the previous 30 days. After ruling out his HVAC system as the cause, he contacted his utility, Duke Energy. Utility technicians arrived quickly and found a partial break in the neutral, which they repaired.
• Andrew C., a Sense user in California, learned that the flickering lights in his home, which he thought were normal, were actually a cause for concern after seeing hundreds of variations in his Power Quality in the Sense app. He contacted his utility who inspected the line to his house, found an issue, and fixed it immediately.

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