DH+ having issues, need some advice

Good morning all,

I'm having issues with one of our DH+ networks. When ever I connect to the DH+ network for our boiler and evaps PLC Processors shortly after I get booted off. The message displayed is "loss of communications to processor". There are 3 PLC 5 processors and a HMI computer on this network as well as a delta v system that communicates to the PLC via DH+. The processors used are a PLC 5/40. 2 out of the 3 processors boot me off the DH+ intermittently with the comms loss message (Evaps and 16Burn PLC). The operators of the boiler use the Delta V HMI to communicate to the PLC. They are trying to light the Boiler but having issues as the comms loss to the Delta V is preventing them to do so. Any tips on trouble shooting a DH+ network or someone with past experiences on this issue would be welcomed.

Thanks, Tex

When ever I connect to the DH+ network for our boiler and evaps PLC Processors shortly after I get booted off

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Are you trying to connect with the programming software thru RSLinx? If so try unchecking "Autobrowse" after RSLINX makes its first connections.
I have seen this happen if you leave "Autobrowse" working.

Yes i'm connecting through Rslinx to the software. Also it is in fact 3/3 of the processors now booting me off randomly. I just tried unchecking auto browse and the same thing occurred. It seems the "16Burn" PLC is the worst of the 3, it constantly loses communication to the processor almost every minute or so. It seems almost as something is brining down the DH+

sparkytex said:

Yes i'm connecting through Rslinx to the software. Also it is in fact 3/3 of the processors now booting me off randomly. I just tried unchecking auto browse and the same thing occurred. It seems the "16Burn" PLC is the worst of the 3, it constantly loses communication to the processor almost every minute or so. It seems almost as something is brining down the DH+

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The first thing I do on any DH+ problem is inspect the network connectors from one end to the other. The phoenix connectors on the cables are notorious for coming loose or being poorly terminated to begin with. I wouldn't do a thing until checking each and every one of those very closely.

With DH+ you can do a lot of things very sloppy with the network and it will still work and might work fine for years and you won't know anything is wrong right up until the day it doesn't work.

DH Plus is a pretty robust network, I would take a hard look at the cable system. Make sure it is properly terminated (one resistor at each physical end), built as a daisy chain or a trunk / drop using SC boxes. Most DH+ challenges usually end being cable related.

Thanks for the pointers guys. I'm going to go inspect the cables, terminations and check the resistors. Will update if I find anything

I'd be a bit concerned about how often the Delta V HMI is polling the PLCs.