What is Error Code 21?
This error means the internal settings of the water heater don’t match the actual installation. It’s often due to incorrect dipswitch or programming settings during install or servicing.
How to Fix Error Code 21
Resetting dipswitch settings or reprogramming should only be done by a licensed technician. In most cases, the error won’t clear until the settings are corrected to match your heater’s setup.
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