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error Aprilaire
Error Code E1
General operational problem, possibly related to wiring or power supply.
? What Causes This
Improperly wired terminal connections or no power to humidifier.
✓ How to Fix It
Verify L1, N/L2 and ground connections are properly wired; check fuse on PCB if necessary.
Source: page 25 of the official manual
From the manual
This error code appears in:
Aprilaire 800