Let's unravel HVACR complexities with Tim R. Skell!
Our expert, Tim R. Skell, spent almost 3 years sharing his expertise in the #FunFactFriday series on LinkedIn. Now, we are giving him a forum to exchange news, knowledge, and passion for HVACR technologies in the new ABB column.
Join the discussion with Tim R. Skell on LinkedIn to read other fun facts and share ideas!
What are some of those most basic 101-type MS/TP mistakes? Wrong baud, positive/negative wires flipped, duplicate MAC ID, duplicate device object ID, or worse case damaged transceiver. None of these issues by themselves are overly complicated, but it still takes time to narrow down to the root cause.
How do you narrow down to the root cause? Some BMS/BAS (Building Management System/ Building Automation System) controllers have built-in diagnostics, but when there is diverse loading on that MS/TP trunk, it may not be as helpful.
Looking at the diagnostics of the end device itself, in this case, the VSD is helpful. A lot of VSDs will have counters that show things like UART, CRC, OK messages, Token counters, Packets received/transmitted, etc.
Based on which counters are screaming up, and which counters are slowly going up, and which are staying steady can narrow down the potential root cause. But there is a faster way.
The ACH580 has a parameter that lets you skip the counters and get straight to the point. Parameter 58.07 will tell you if the drive is sensing a baud error, flipped wires, duplicate addresses, noise on the wire, parity error, etc.
You can read more in the ACH580 HVAC control program: Firmware manual at page 602.
Yes you can still go to those trusty counters if that’s your preferred method of troubleshooting. But consider saving yourself some time in troubleshooting and check out 58.07 first. This is one of ABB Tech Support’s secret weapons in helping folks troubleshoot comms issues. My goal is to make this feature not so secret!
Bonus tip
When the start/stop and reference signals are commanded over comms, and things aren’t working as expected – check out Group 06 for the Control Word and Status Words to see what the ACH580 is seeing over comms. I.e. did it really see a start command or not.
