I’ve been working on a retrofit where we needed to pull BACnet points from a Daikin HVAC unit, apply custom logic, and write commands back without modifying the OEM controller or BAS. There was a need to feed the process PLC data from the HVAC as well.

I ended up using a gateway + PLC to overlay the sequence.

Curious how others are handling similar situations — are you reprogramming BAS, using programmable controllers, or just living with OEM sequences?

 

Can you explain a bit more? Was protocol conversion required, which is why you needed a gateway? Did the Daikin HVAC unit replace a unit from a different manufacturer (or different, incompatible model from the same manufacturer), and so it needed to appear to the BAS as if nothing had changed? What type of custom logic had to be applied (e.g. different scaling, remapping of data to different objects, instances, or protocols, etc.)?

 

So the Daikin unit was a new install. The Daikin Microtech control was setup for BACnet MS/TP. The process equipment inside utilized a click industrial PLC that was Modbus RTU capable. I utilized a Babbel Buster BB3-3101 to pull the BACnet points from Daikin and map to modbus. The click then pulled this data to perform logic and capture values for the process then write back to adjust the Daikin parameters accordingly. This process is being done without integration into the existing BAS.

 

Thanks for the additional details. What you've done seems like the typical approach I've seen.

Depending on the logic required, though, it may have been possible to do this with just a gateway that, in addition to protocol conversion, also supports PLC-style logic built-in, without needing the Click PLC at all. ICC's gateways, such as the Mirius or ETH-1000, support PLC-style data manipulation operations called Database Logic that can be used to apply custom logic and manipulate the data retrieved from, or sent to, the device(s) its communicating with. Additionally, that data can then be exposed via any of the supported protocols to a PLC, BAS, or other control systems.