At what model or firmware did AB PLCs start faulting on power-up?

[ryangriggs]

In the past I have been familiar with the 1769-L35E series CompactLogix PLCs by Allen Bradley. For those PLCs (firmware version 20.19), when the unit is power-cycled while in Remote Run, it simply starts running again once power is restored.



However, according to a recent experience as well as the Fault Manual [page 17], I discovered that a newer L30ER PLC (firmware version 33), by default, enters a Major Fault state when power cycled while running (Type 01, Code 01 - "Power Up Fault: Power lost and restored in RUN mode") and required user intervention to restore the PLC to running state.


After discovering this, I created a power-up fault handler to ensure the fault is cleared and allow the PLC to enter Run state immediately upon power-cycle.



Does anyone know when/why this behavior changed (i.e. which firmware level or PLC model)? This is a huge change in operation, and I can see it causing major problems if programmers fail to notice and/or address it, especially in remote installations. The fault manual states applicability to the entire 1769 PLC family (as well as other families) but doesn't mention specific models or firmware levels at which this change occurred.



Thanks for any insight.

 

[KuulKuum]

Does anyone know when/why this behavior changed (i.e. which firmware level or PLC model)?

I cannot answer the when/why this change, but you could change the controller behavior by; in the Controller Properties > Advanced and change the "Power-Up Handler: to <none>

 

[ryangriggs]

I cannot answer the when/why this change, but you could change the controller behavior by; in the Controller Properties > Advanced and change the "Power-Up Handler: to <none>

To confirm, you're saying if Power-Up Handler is set to <none> it will not enter the fault mode, and will immediately run on startup?


If so, this seems to contradict the document I referenced, as it states that leaving the Power-Up handler "empty" will prompt the major fault:

The Power-Up Handler is an optional task that executes when the controller
powers up in Run or Remote Run modes.



To Do this:
Prevent the controller from returning to Run or
Remote mode
Leave the routine for the Power-Up Handler empty. When
power restored, a major fault (type 1, code 1) occurs and the
controller enters the faulted state.



To Do this:

Direct the controller to take specific actions, then
resume normal operation when power restored
In the Power-Up Handler fault routine, complete these steps.
1. Clear the major fault (type 1, code 1).
2. Run the appropriate logic for the specific actions required.


​

To clarify, I did have a Power-up handler routine defined on this PLC, which initialized some tags. However, it did not handle faults.


So are you saying that simply enabling a Power-Up Handler causes the system to Major Fault on power up, and that setting this option to <none> avoids this fault?


At the very least, I would say the documentation is confusing about this. Would you agree?

 

[ryangriggs]

UPDATE: I can confirm that this is indeed the operation, even for the old L35E firmware version 20:


If any Power-Up handler routine is defined, the system automatically faults at power-up. Such faults must then be handled within this routine.


This is borne out by the RSLogix 5000 manual:

Powerup Fault

A major recoverable fault generated by the controller if it powers-up in run or test mode and it has a Power-up Handler Program configured. The Power-up Handler Program must clear the fault or the controller will power up in Faulted mode.

But this behavior is not indicated in the Power-Up Handler manual info:

Power-Up Handler Program

A program that can be configured to handle startup execution after an abnormal loss of power in Run mode.

Configure a Power-Up Handler Program

You can configure a program as the Power-Up Handler program. This program will be executed on startup after losing power abnormally in Run mode.
To configure an existing program as the Power-Up Handler program, do the following:
Note: The program cannot be scheduled under a task.

1. From the Edit menu, choose Controller Properties.
2. Click the Advanced tab.
3. From the Power-Up Handler Program pull-down menu, choose the program you want to use.

Note that a program must already exist in the Controller Organizer Power-Up Handler folder in order for it to be available from this menu.

1. Click the OK button.

Routines in the Power-Up Handler program should perform any startup logic required to reset the system to a useful state after a power loss.

 

[KuulKuum]

You are Correct... but my first statement is still TRUE.

IF you "Create" any Power-Up Handler routines you have to handle the Faults in said routines, or the controller will stay in a power up fault until user or program handled.

If you "Delete" all Programs/Tags from the Power-Up Handler then setting <none> in the controller properties>advanced>power-up handler will allow the controller to recover and run from a system power fault/reset.

But, RA could have changed things, as I am not running the latest version 35 of Studio 5000

edit: This KB explains.
ID: QA3838 | Access Levels: TechConnect
Major Fault Type 01 Code 01 Power-Up Fault
https://rockwellautomation.custhelp.com/app/answers/answer_view/a_id/22379/loc/en_US#__highlight

and this for those that need to "Delete" Power-Up Handler programming.
ID: QA8920 | Access Levels: TechConnect
Studio 5000: Removing Power-Up Handler or Controller Fault Handler from Project
https://rockwellautomation.custhelp.com/app/answers/answer_view/a_id/54061/loc/en_US#__highlight

 

[ryangriggs]

@KuulKuum
Thanks for the info. Unfortunately I don't have the requisite subscription to read these docs. :/

 

[plvlce]

edit: This KB explains.
ID: QA3838 | Access Levels: TechConnect
Major Fault Type 01 Code 01 Power-Up Fault
https://rockwellautomation.custhelp.com/app/answers/answer_view/a_id/22379/loc/en_US#__highlight

"The following information on Power Up Routines is documented in publication Logix 5000 Controllers Common Procedures Programming Manual , publication 1756-PM001"

Gotta love how Rockwell will paywall a technote then tell you where you could've found the information for free.

Unfortunately I don't have the requisite subscription to read these docs.

The first one basically tells you what you already figured out -- if there's a defined power-up routine that fault is generated, so you have to either handle that fault or get rid of the routine.

The second one details how to get rid of a power-up routine: delete any routines, move the program into MainTask, unschedule it, then delete it from the unscheduled programs.

 

[ryangriggs]

@plvlce Thank you.