Dimming is an annoying problem, but not necessarily dangerous. You might just choose to live with it. We see it most often in older homes with 100-amp service and a large central air conditioner. A 4-ton air conditioner, for example, can briefly exceed the rating of the electrical system at start-up, but not long enough to trip a breaker. Plus, the LRA grows further as the compressor ages.
In newer homes with 150 or 200-amp electric panels, it may require some detective work by an electrician to figure out why the lights are dimming. Our electrician friend, Craig Eaton, suggests to start by checking the wire connections at the panel and the condenser circuit. Repairing a loose or deteriorated connection could solve the problem. Also, running heavier gauge wiring would definitely fix it, but that’s an expensive and labor-intensive solution that is impractical.
There are two different devices that an air conditioning contractor or electrician can install to eliminate light dimming. One is called a “hard start kit,” which is a capacitor on steroids. Every heat pump or air conditioning condenser unit has a capacitor built-in that adds an extra surge of current needed at start-up. A hard start kit is a super capacitor that stores and then releases a larger bump. It is the cheaper of the two solutions.
The second choice is the “soft start kit,” a more sophisticated system that uses a programmed circuit board to measure the characteristics of the compressor motor. It then optimizes the electrical input of a start capacitor over several start cycles, causing the starting inrush current (LRA) to be significantly reduced. We suggest you ask your trusted electrical or air conditioning contractor which is best for your system.
To learn about other defects that can cause lighting fluctuations, see our blog post “What causes flickering or blinking lights in a house?”
While we hope you find this series of articles about home inspection helpful, they should not be considered an alternative to an actual home inspection by a local inspector. Also, construction standards vary in different parts of the country and it is possible that important issues related to your area may not be covered here.
© McGarry and Madsen Inspection
