Solar Lattice

FailureMode

Daisy-chain communication break

ID
fm:daisy-chain-communication-break
IRI
https://solarlattice.org/kb/fm/daisy-chain-communication-break
Status
active
Also known as
daisy-chain communication issues, line break after last communicating device, bad port in the SWDM, mixed inverter generations in one chain

A daisy-chain communication break happens when one link in a chain of networked inverters fails. Inverters downstream of that link, or the faulty unit itself, then stop reporting to the cluster controller. Common culprits are Ethernet cables or RJ45 crimps, unseated or kinked ribbon cables, the data module (often a bad port), the display, or the inverter's communication board. On RS-485 chains, noise builds up as more inverters are added, and star or T wiring causes signal reflections that disrupt communication. Start with a full power cycle with AC and DC both off. Then reseat the ribbon cables and check or replace the Ethernet cables, keeping signal cables away from AC wiring. To find the faulty part, swap the suspect data module and display into known-good inverters further down the chain, or isolate the inverter and connect a laptop to it directly. An in-line coupler can bridge around a faulty inverter so the rest of the chain keeps working. During commissioning, connect only at an open port at the end of the chain. On long RS-485 chains, use isolated repeaters and shielded twisted cable.

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Claims

presents_as

c1 drafted · lead Communication loss

One or more inverters on the daisy chain stop reporting to the cluster controller or Sunny Explorer, while possibly still producing.

affects

c2 drafted · lead Communication interface module

A bad port in the Speedwire-Webconnect Data Module (SWDM) is named as the typical cause of a chain interruption.

One of the other two inverters may be interrupting the daisy-chain, which is typically caused by a bad port in the SWDM.

c3 drafted · lead Network cable

Faulty Ethernet cabling or poor RJ45 crimps between inverters can break the chain.

c4 verified · fact Internal communication cable

Ribbon cables to the display are part of the communication path and must be fully seated and undamaged.

verified by: review-workflowverified on: 2026-10-24

c5 drafted · lead Inverter display proposed

On STP-US-10 the display is blank but still part of the communication pathway.

caused_by

c6 drafted · lead Internal connector or ribbon cable unseated

Ribbon cables not fully seated, kinked or damaged can stop communication through the display.

c7 drafted · lead Improper crimping

Questionable RJ45 crimps or cable strain on the crimp degrade conductivity.

c8 drafted · lead Signal cable electromagnetic interference

Signal cables run near AC power cables, and noise that increases with each inverter added to an RS-485 chain, compromise communication.

c9 drafted · lead Installation error

Star or T connection schemes cause signal reflections; plugging into the middle of a chain during commissioning disconnects inverters from the cluster.

detected_by

c10 drafted · lead Known-good component swap test

Swap the suspect SWDM and display into inverters further down the chain to see which component follows the fault.

c11 drafted · lead Communication test proposed

Isolate the suspect inverter and connect a laptop with Sunny Explorer directly to its SWDM port to check whether the inverter itself communicates.

mitigated_by

c12 verified · fact Inverter restart

Do a power cycle with both AC and DC off before further troubleshooting; extend to the whole chain or site if the issue persists.

verified by: review-workflowverified on: 2026-10-24

c13 drafted · lead Communication cable check

Disconnect, inspect and reconnect Ethernet cables at both SWDM ports; try a known-good cable or re-crimp RJ45 jacks.

c14 drafted · lead Proper cable routing

Keep signal cables away from AC cables and out of power conduits; use twisted, shielded cable away from noise sources.

c15 drafted · lead Communication bus termination and cabling practice

Use point-to-point daisy chaining with matching polarity, avoid star or T topologies, terminate cable ends where needed and keep the chain short.

c16 drafted · lead RS-485 isolated repeater proposed

Repeaters isolate noise and boost RS-485 signals on chains with multiple inverters.

c17 drafted · lead In-line coupler bypass proposed

Temporarily join both sides of the chain with an in-line coupler to jump over a faulty inverter.

c18 drafted · lead Contact manufacturer service

Report the faulty SWDM, display or inverter to the manufacturer service line if the steps do not resolve the issue.

Data