Short circuit

On SMA Sunny Island US systems, the communication bus reports a short circuit either as error F930 or as the lower-level warning W946. If the short circuit is on the load side, the Sunny Island cannot hold the voltage on the affected line conductor. The supply to the Multicluster-Box contactor Q10/Q110 then fails and the cluster is reported as incomplete. Look for the short circuit in the loads and in the stand-alone grid wiring first, and also check that connection AC2 is not shorted. Clear the short circuit before restarting. On the DC side, insulation failures come from short circuits. These usually happen when humidity meets damaged or aged DC cables or connectors. Inside a module, a bypass diode can fail shorted. This happens when the diode is physically shorted in the junction box, mounted the wrong way round, or hit by lightning or static discharge. Shorted diodes are reported more often than open ones. Short-circuit currents in a battery can cause heating and electric arcs. Remove metal jewellery and use insulated tools and gloves when working on the battery.

<!-- review notes

• sentence 1: support check: partial - F930 and W946 are the short-circuit codes, but the passages say they are SiCom messages, not that the 'communication bus' reports either code, and they do not mention US units.
• sentence 3: support check: partial - Eliminating the short circuit and checking AC2 are in the passages, but the AC2 check appears in an overload context. The instruction to look in the loads and wiring first and to clear the fault before restarting is not clearly stated.
• sentence 1: review: partial - F930 (level 3) and W946 (level 1) are short-circuit messages 'via SiCom', but the rows do not call SiCom a communication bus, and the quoted text does not mention US systems. -->