Fault Code 4220

Fault: Abnormal bus voltage

For Mitsubishi split and multi-split air conditioning systems included wall-mounted, duct-connected, console split, bulkhead, ceiling mounted and multi-head split units.
If molded case circuit breakers or earth leakage circuit breakers have tripped, do not reset the breaker immediately without first checking for any problems with insulation of equipment.
Resetting breakers without a check of insulation may cause damage to equipment.