The A.O. Smith line of water heaters is a broad one, covering both residential and commercial use and electric and gas options. If your home has an A.O. Smith electric water heater installed, you can adjust the temperature in a matter of minutes as long as you have access to the heater's panels. Tankless models may not even require tools.
Preparing to Adjust Water Heater
Before you begin, you must turn off the power to your water heater. Adjusting the thermostat requires access to the heater's electrical system, and if the power is live during the process, you'll run the risk of a serious and perhaps lethal electric shock.
If your electrical panel uses breakers, locate the breaker that controls your water heater — it should be plainly marked — and turn it off. If you have an older panel that uses glass fuses, locate the fuse for your heater and remove it. If you have any doubt about the correct breaker or fuse, use a multimeter or other test device at the wiring terminals to verify that there's no live current. After you've confirmed the correct fuse or breaker, label it for future reference.
Adjusting Your Water Heater's Thermostat
Once you're confident that power to the heater has been shut off, remove the two access panels from the tank with a Phillips screwdriver and fold back the insulation to reveal the thermostats. Most A.O. Smith water heaters have two, but some may have only a single thermostat located behind the lower access panel.
The thermostat's control is a small screw set into a covered housing, and you'll need a flathead screwdriver to turn it. Temperature adjustment is simple and intuitive; you'll turn clockwise to increase the temperature and counterclockwise to lower the temperature.
On a two-thermostat model, such as the 55-gallon PNT-55, you'll need to adjust the lower thermostat to match the upper one. Again, fold the insulation out of the way and use a flathead screwdriver to adjust the temperature. The temperature settings for both thermostats should be as close as you can make them. If the upper thermostat is set to a higher temperature than the lower, you might sometimes find yourself short of hot water. Once you've finished, replace the insulation over the thermostats, screw the cover panels back into place and restore power to the water heater.
Increase Water Temperature With Caution
The default temperature setting on an A.O. Smith electric water heater is 120 degrees Fahrenheit. That's partly to reduce power consumption, but A.O. Smith's owner's manuals describe that temperature primarily as a safety feature that minimizes the risk of scalding. A modest increase in temperature from 120 to 130 degrees reduces the time needed for a serious burn from over five minutes to just 30 seconds or so.
By all means, feel free to increase the temperature if you need that added hot water capacity or if you're concerned about bacterial growth, but for safety's sake, you should install thermostatic mixing valves. These cut the hot water with cold at the faucet to keep the water temperature at a safer level.
A.O. Smith Tankless Water Heaters
Most of A.O. Smith's tankless water heaters run on propane or natural gas, but a few models are electric, such as the ATI-240H. If you have one of these tankless models, adjusting the temperature is simpler. It requires no tools, and you won't need to shut off power to the unit.
The heater's display, or user interface module, has a simple LED display showing the set temperature — again, 120 degrees is the default — as well as up and down arrows and an "Enter" button. Press the up or down arrows to change the temperature by one degree at a time or hold them down to scroll rapidly. Once you've set the temperature you want, press the "Enter" button to confirm the new temperature setting.
Fred Decker is a trained chef and prolific freelance writer. He was educated at Memorial University of Newfoundland and the Northern Alberta Institute of Technology. His articles have appeared on numerous home and garden sites, including OurEverydayLife, GoneOutdoots, The Nest and eHow, as well as the San Francisco Chronicle's SFGate.com.