Furnace ac safety shut-off damaged missing : Emergency and safety disconnect switches installed on heating and air conditioning systems are helpful even necessary in several ways. Service personnel are more surely protected if a disconnect switch has been set to the off position rather than them relying on a tripped circuit breaker that may or may not be the right one. Oil burning units must (by code) have disconnect switches installed to prevent run on situations. This particular switch should be outside the room where the equipment is installed. If the oil burning equipment is in a basement placing the switch at the top of the stairwell is generally okay. In the case of an air conditioner either a method to shut off power should be within 5 feet of the unit or the main breaker should be within view of a person touching the unit. Missing, broken or improperly placed switches should be installed or Repaired as soon as possible.