Navien E421 Error Code
Cold waterinlet1:thermostat Contact Technical Support at 1-800-519-8794. openors
Source: npn-199e__navi-npn-199e-english-iom.pdf
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Hotwateroutlet:thermostat Contact Technical Support at 1-800-519-8794. openorsho
Cold water inlet2:thermostat Contact Technical Support at 1-800-519-8794. openor
Abnormal operation:water ContactTechnicalSupportat1-800-519-8794. adjustment val
Abnormal operation: circulation External: Ensure that all watersupply and return
Abnormaloperation:flowsensor ContactTechnicalSupportat1-800-519-8794. Error Code