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Lost our program during Generator Test (switching to generator power). Has worked fine last 3 years.  We have a V570-57-T20B-J controller.  It went to a "text" only "Stop Reasons:  No Application.

Status:    Idle.   We have received a "software" program from distributor to upload from PC to PLC but are having no luck after 'physically' connecting PC to PLC  accomplishing an  upload. I am very new to this PLC world and need lots of help. Any suggestions, info available for proper steps?  

P.S.  We also have  an identical(redundant) program and boiler next to this one. Could we download program from it onto  a SD card and load  it onto our failed PLC??

Thank YOU!

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  • MVP 2023

Moved to correct area.

Hi Rick, a few things.  This PLC is a Vision system. 

I'm assuming that the "distributor" is not a Unitronics distributor, but one that uses the PLC in their generator control system.  In sending you a project to reload into the plc, they should have provided all details needed to get you back up and running.  If they haven't I think that's a bit slack. 

To help you we need some more info.  How was the "software program" delivered?   A file sent as an attachment in email?  On an SD card?  What communications are on-board....serial?  Ethernet?  

The program that communicates to the PLC is Visilogic found on the Unitronics website found here:


 However, there are many versions of the program as various changes are made over the years.  If you don't get the exact version that matches what was originally in your PLC, you will likely/possibly get into issues with the project that runs the PLC not working as expected.

For now please let us know some answers.  Please also remember that this forum is mostly attended by volunteers, with limited input directly from Unitronics.

cheers, Aus




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  • MVP 2023

In addition to what Aus says -

If the PLC lost its program it probably needs a new battery - CR2450N.  Depending on how old the PLC is you may or may not have to pop the back on the PLC housing to get to it.  Newer V570s have a little battery door.  The original programmer should have done a "download and burn" to prevent this.  With the Unitronics brand of PLC, we generally do edits and download only to the battery-backed memory because it's much quicker.  When you're reasonably done with your program you "burn" it into the flash memory.  It takes about 15 minutes.  This is not a permanent thing, as you can "burn" again if modifications are needed.

In order to use the SD card the programmer had to put a function block into the program to allow it.  This may or may not be there.

I am a Unitronics distributor in the US.  If you are also in the US and want me to have a look at the program PM me with it.

Joe T.


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Joe & Ausman, 

Thank you both for replying so promptly. We did replace battery(even though old one still read 3 volts.)  We cannot reach our "original" programmer/controls guru-he is not responding to calls, bit of a mystery as he branched out on his own as an "independent" contractor I believe? So, have not been able to locate a "download and burn" backup?

Program to download was obtained via email with  attached link. We physically connected from PC to PLC via USB to mini-USB cord. 

How do I  determine if "function block" for SD card  was put into the program? It is included as an option in grahics.  And, if so, could we "download"  program from existing PLC  unit with same setup and then "download" from SD card unto our failed PLC?

And Joe, we may very well need to PM you our program if our current AB rep isn't successful. We are located near Indianapolis, IN....and you? They are supposed to be assisting us with this situation today....we will see. 

Thank you again for the input. This being a "new" approach to troubleshooting & sharing info for me! Have greatly appreciated the assistance. 


In His Grace, rw 

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Joe & Ausman, 

Thank you for your previous valuable input concerning our "loss of programming"  in our boiler  PLC we believe was related to our full-load generator test. We have  received the "reloading" guidance/assistance needed from our local Unitronics Rep through DS Mechanical Service  connecting us to them.  Our PLC initially looks corrected and our boiler running normally. 

Again, I appreciate your assistance and am thankful for this growing experience...

In His  Grace, rw

Riverview Health  Hospital, Westfield,IN


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