When someone asks me about central plant control, my first thought is always of a Johnson Controls DX9100. The DX9100 standalone controller has been around since the early 90’s and is still being installed today. Although this impressive controller brings great flexibility to the table, it lacks in ease of use. Walking into a retrofit opportunity and finding a DX9100 without any reference material can be very intimidating. What makes this so troublesome is the fact that the DX9100 does not store its tag file within the controller. Without an existing tag file your ability to assess your system just got tougher.
The best approach in this situation is to build a tag file from scratch. Start with the field devices themselves and work your way backwards in a reverse engineering type fashion. Once you have your hardware points labeled you can begin to use the DX9100 trace feature and start making sense of the module logic itself. Unfortunately labels are limited to 8 characters, so make sure each label is unique to it’s specific function module origin and in a logical format that you understand.
It may seem like an overwhelming task, but this process provides you with a better understanding of the system your working with. In many cases I have found improperly installed field devices and even the wrong device installed altogether. This also exposes an opportunity to take a look at the current sequence of operation and make any changes needed to improve overall plant operation. So before you turn your back on a nice DX9100 retrofit project, remember first, that a loosely documented DX9100 job isn’t as bad you think.
If you are a Stromquist customer or are in GA or FL, call your Stromquist rep for help with your DX9100 needs. All others, please refer to one of our affiliates at the Controls Group North America site to find a distributor in your area.