nLight communication is initiated by a polling device. That is a device that that requests information of non-polling devices. This would be a output device of any kind (anything with a relay or dimming connection), a bridge, a gateway or any wifi device. If you have a zone full of non-polling devices, communication is never initiated and all devices will show a comm error (rapid flash - two blinks). For example: A zone full of sensors or switches powered by a nPS80 will show a comms error on all devices. Most devices that provide bus power are polling devices, so this is rarely an issue. But, the nPS80 provides bus power and is not a polling device. This makes troubleshooting a zone for a comms error slightly different when a nPS80 is being used.
Why is this important? Why would there ever be a zone full of non-polling devices? There are some cases where global channels are used on a zone full of sensors or switches. For example a master switch control station with multiple nPODMs or a single occupancy sensor at a building entrance. If a nPS80 is used either because of need for more bus power than what the bridge can offer, or because of over design, then these conditions will exist. The bridge is a polling device, so that once the zone is plugged into the bridge, everything will work correctly. During installation this can be confusing. It appears that there is a cat5 issue prior to being plugged into the bridge. It is important to know that this zone will need to be plugged into a bridge to properly diagnose the cat5. If there is an issue with that bridge port causing communication to stop, the comms error will appear as well. A typical zone would not necessarily show a comms error when it loses communication with the bridge, because it can be its own local zone with polling devices. A nPS80 zone with non-polling devices will show a comms error when unable to communicate with the bridge because there a no polling devices left on the zone. Also, imagine a zone that does not have enough bus power and a nPS80 is used. If there is a disconnect in the cat 5 between non-polling devices being powered by a nPS80 and polling devices, troubleshooting could be difficult. Typical troubleshooting method would be to remove cables to isolate and find the issue. In this case, that will have no effect. The comms issue will continue until the cat5 with the open is replaced.