Last year you installed a new whole-house humidifier for a homeowner who was bothered by excessive static electricity. The installation required a sheet metal elbow and a few other design modifications but the job is done — all shiny, neat, and paid for. Good job, good profits.
This heating season, though, you get a call from the same customer, who says the home’s humidity is still too low, will you please send a tech to check out the humidifier.