AO Smith Tankless Rack System - Back-to-Back: General Maintenance

Turn OFF the power supply, the gas supply, and the water supply.
Disconnect the power cable. If you have an outdoor model, verify that the electrical connections are not powered by checking them with a non-contact circuit tester. ᴏ Indoor Model: Simply unplug the power cord from the outlet. ᴏ Outdoor Model: Disconnect the power cable at the bottom of the water heater. See the water heater’s Installation Manual and Owner’s Guide for details.
Disconnect the gas, cold water, and hot water connections.
Remove the bolts as described below. The locations are shown by the arrows in Figure 6. If you have a wall mounted rack, see Figure 8.
During this step, hold and support the water heater so that it does not fall. ᴏ Free Standing Rack: Remove the six bolts that secure the water heater. ᴏ Wall Mounted Rack: Rotate each T-bolt 90-degrees to release the water heater from the rail. Look at the indicator at the end of each T-bolt to determine its orientation. The indicator should be parallel with the T-channel. See Figure 7.
Lift the water heater from the rack.
Secure the new water heater to the rails. If the heater is being mounted on a wall mounted rack, refer to Figure 8.
Connect the water, gas, and electrical connections as outlined in the water heater’s Installation Manual and Owner’s Guide.
Return the water heater to service and verify proper operation.