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SLS 1508 BMS Errors

We have started getting the following error after years of service.  These never shut down our system but I am afraid something is wrong and will eventually cause us issues. 

FAILED   Both SIS Net Connections on Logic Solver are Bad

MAINT     SIS Net Error

ADVISE   SIS Net High Error Rate

Seem to be getting a lot of P2Pstatus alarms as well which I believe is the communication between the modules?

We have 4 redundant pairs of 1508s and each one gets these errors, sometimes all at the same time but not always.  Any ideas of what might be causing the problem?

2 Replies

  • The logic solvers communicate to the SISNet Repeaters over the Safety Bus. This involves the connectors between the carriers and the two repeaters. This would also involve at least two sets of SISNet repeaters (otherwise, what's the point...). The SISNet is a fiber wiring, so damage to one fiber connection would not disrupt communication and you would need to lose all connections to lose all communication.

    So I'm thinking the issue has to be with the Local Bus carriers, which is the only common components affecting both SISNet communications.

    Check that the two-wide SISNet carrier is properly seated and fully engaged with the 8 wide carrier. There should be DIN rail stops on both ends of the Carrier chain to keep them from coming apart. Sometimes these come loose over time and vibration could cause separation of carriers and intermittent contact. At least, eliminate this a possible cause.

    Make sure grounding connections are secure and have not come loose. Again, degradation of connections can lead to increased resistance in the ground path and accentuate noise issues that end up disrupting communications. Something to check and eliminate.

    Check these at each set of SISNet Repeaters. If there were no errors on one or the other safetyBus connections to the SISNet repeaters, and suddenly you see errors affecting both, it seems highly unlikely that you have two separate issues, one on the primary and the other on the secondary, causing loss of both.

    Is your SISNet Fiber ring made up of two separate and divergent paths or one multi-core Fiber network? Could a single cable be damaged such that all fibers are compromised, causing increased DB loss and possible increase in error rate? Not likely. Would fiber degradation occur identically over time resulting in all fibers experience same level of loss at the same time. Not likely. Although you should check Fiber integrity and ensure end connectors are clean, issues with terminations would not occur simultaneously across both SISNet rings.

    Andre Dicaire