Daikin Heat Reclaim Ventilator Error Code A8

Full Diagnosis

Power supply fault or AC input overcurrent detected on the heat reclaim ventilator's control PCB. The HRV is a stand-alone air-to-air energy-recovery unit — it draws in outdoor air and exhausts stale indoor air through a total-enthalpy heat exchange element, with no refrigerant circuit or compressor of its own. When A8 trips, the unit shuts down its supply and exhaust fans and drops any energized outputs to prevent further damage to the PCB or wiring from the abnormal current draw. Unlike A9, which points to the electronic expansion valve fitted only on models with an integral cooling/heating coil, A8 is a base power-supply/PCB fault common to every HRV regardless of coil configuration.

All Recorded Causes

Incoming AC supply voltage out of range (sag, surge, or wrong voltage tap) Loose, corroded, or miswired signal-line connection feeding the control PCB Damaged, pinched, or improperly terminated power wiring to the unit Short circuit in the fan motor or damper circuit pulling excess current back through the PCB Failing control PCB no longer regulating input current correctly

Verify Before Replacing Parts

1. Confirm the exact Daikin model family and heat reclaim ventilator context before acting on a generic code description.
2. Verify airflow first, then confirm operating pressures and temperature relationship before adjusting charge, since incoming AC supply voltage out of range (sag, surge, or wrong voltage tap).
3. Look for restrictions, iced coils, or dirty heat-transfer surfaces that can mimic a charge problem, and separately confirm loose, corroded, or miswired signal-line connection feeding the control PCB.
4. After the correction, run the system long enough to confirm the heat reclaim ventilator fault does not return under normal load.