SMA [Inverter not connecting to the grid]what to check

An SMA inverter that will not connect and start generating is often not broken but blocked, and the distinction matters because it changes what you do next. SMA run checks before connecting to the grid and disable the connection if one fails — their wording for the insulation case is that if the values are below the specified threshold, the grid connection is disabled to prevent ground faults. The system sits there, apparently dead, having made a decision. The problem for an owner is that modern SMA inverters have no display, so all you get is a light. SMA connect the two for the most serious family: if the red LED is glowing and event 3501, 3601 or 3701 shows in the Results menu, there may be a ground fault present. But a light on its own cannot tell you which of several conditions applies, and the answer is in the event number rather than the colour. There are two places to find it and both are worth knowing. The inverter has its own web user interface with a Results menu, reached over the local network. And if the system is registered, Sunny Portal carries the event messages in the system logbook or event monitor.

SMA describe both as valid routes. Getting the number changes the conversation entirely, because it separates a grid condition from a DC-side fault from a communication problem, and those go to three different people. The Sunny Boy 3.0 to 6.0 operating manual names the ones that produce exactly this symptom. Event 1302 is waiting for grid voltage, check grid and fuses — SMA's explanation is L or N not connected, and their first corrective measures are to ensure the line conductors are connected and the miniature circuit breaker is switched on. Event 1501 is a reconnection fault, where the country data set or a parameter does not match local requirements and the inverter cannot connect. Events 3302 and 3303 are unstable operation: not enough power at the DC input for stable operation, so it cannot connect. And events 3901 and 3902 are waiting for DC start conditions, which SMA's own article describes as typically appearing at dawn and dusk, when the inverter's electronics are awake but the array is not yet delivering enough voltage, with the corrective measure that it is generally sufficient to wait for more light, or to check for snow in winter.

The green LED flashing two seconds on and two off is SMA's waiting-for-feed-in-conditions signal for the same state, and green and red flashing together means no country data set is configured. A structural observation that helps when you are reading a list: SMA's event numbers run in bands. The 35xx range covers insulation, 36xx leakage current, 37xx residual current, and the 6001 to 6499 and 77xx ranges are self-diagnosis events whose cause, in SMA's words, must be determined by the Service. That banding is an inference from the article set and the manual rather than a legend SMA publish, but it is a reliable orientation. Two honest limits. SMA's articles are model-specific, so the same event number has separate articles for different inverter families and the family matters. And part of their event documentation sits behind an installer login, which means some detail is genuinely not public.

1. 1

   Check the light on the inverter and note the colour. It will not tell you which fault you have, but a glowing red is what SMA tie to the ground fault family.

2. 2

   Find the event number. It is in the Results menu of the inverter’s own web interface, or in the system logbook or event monitor in Sunny Portal if the system is registered.

3. 3

   Note whether the system generated at all today and whether it stopped or never started. A failure to connect and a mid-day dropout point at different event families.

4. 4

   Rule out the obvious — heavily overcast conditions, early morning, or a tripped breaker on the AC side of the inverter. A green LED flashing two seconds on and two off is SMA’s waiting-for-feed-in-conditions signal, and their advice for the dawn-and-dusk events 3901 and 3902 is simply to wait for more light.

5. 5

   If a restart is worth trying, do it the way SMA publish it for owners: switch off the inverter’s circuit breaker in the consumer unit or sub-distribution board overnight and switch it back on the next morning. SMA’s reason for the overnight wait is that the inverter is then disconnected on the DC side as well, because nothing is generated at night, and the capacitor discharge time has been observed. Their other route, disconnecting the inverter from its voltage sources in daylight, is one they say to ask your installer for.

   Switching the breaker off makes the inverter safe to stand next to. It does not make the array safe — the DC side stays live in daylight, and SMA warn against touching the cables, the substructure, the frame or the modules where a ground fault may be present. Do not operate the DC switch on the inverter as part of this.
6. 6

   Give the event number to your installer rather than describing the light. It is the single piece of information that tells them what to bring.