Some devices have an optional HAND-OFF-AUTO (HOA) manual override switch that enables you to control equipment at the automation station.

The HOA override switch is not to be used as a safety device when performing maintenance. If the HOA switch is used as a safety device, it can result in serious injury to personnel or cause damage to property or equipment. Always follow safety procedures when performing maintenance.

The HAND status identifies a point being controlled by an HOA manual override switch and not the system. The HOA override switch is only method you can use to control whether a point is placed into or taken out of HAND status.

  • Points cannot be commanded to HAND by using an operator interface.
  • Points cannot be commanded to or removed from HAND status by using program statements.

Before attempting to command points that contain HOA override switches, check the status of the controller to ensure that the point can be commanded.

The HAND status appears as part of the overall point status. This status indicates that an HOA override switch is controlling a piece of equipment. The equipment cannot be controlled through the operator interface or PPCL until the HOA override is switched back to the AUTO position.

When a point is at HAND status, PPCL continues to issue commands to that point. Since the HOA override switch is controlling the point, the PPCL commands do not take effect. When the HOA override is switched back to the AUTO position, the last command issued to that point, while in HAND status, is executed.

See Table 1-9 for a comparison of the point status while using the HOA override switch.

Table 1-9.  Point Status with the HOA Override Switch.

HOA Switch Setting

Point is being controlled by…



HOA Switch

Digital points: *ON* or *OFF*

Analog points: Value of the current HAND position. This value could differ from the last commanded value.


HOA Switch

Equipment being controlled is OFF.


Operator interface or PPCL

Equipment is being controlled by operator interface or PPCL.

Be aware of how your system will react before attempting to control equipment by using an HOA override switch.

Manually controlling equipment can cause the system to react in an unstable manner. Once control is returned to the system, you may need to perform other functions before normal operations can resume.