How to Reset an SMA Sunny Boy Inverter

SMA Sunny Boy inverters are famously reliable, which makes it all the more confusing when one locks up, drops off the monitoring portal, or sits in standby for no obvious reason. A controlled restart resolves most of these situations — but SMA’s documentation carries an important warning that other brands do not: under fault conditions, you must not operate the inverter’s own DC load-break switch, and must disconnect the PV array through an external disconnection device instead. This guide follows SMA’s official line.

Quick Answer

To restart a Sunny Boy with no active fault: switch the dedicated solar AC miniature circuit-breaker OFF, then open the DC load-break switch on the inverter (or remove the Electronic Solar Switch on older models). Wait until all LEDs and the display are completely dark — the internal capacitors take several minutes to discharge. Then reverse the order: close the DC switch first, then switch the AC breaker back on. The inverter runs its startup checks and reconnects to the grid automatically. Critical SMA safety rule: if the inverter is showing a fault or error, do not operate the DC load-break switch on the unit — disconnect the PV array via the external DC disconnection device, switch off the AC breaker, secure it against reconnection, and call a qualified person.

Know Your Model’s DC Disconnect

Sunny Boy generations differ here, and using the wrong method is exactly what SMA warns against. Current-generation Sunny Boy models (such as the SB 3.0–6.0 series) have a rotary DC load-break switch built into the inverter — this is the switch the manual’s commissioning and decommissioning procedures refer to. Older models (SB 3000TL, 4000TL, and similar) instead use the removable Electronic Solar Switch: a plug-in handle on the bottom of the unit that you pull out to break the DC circuit. Check which one you have before touching anything — the Electronic Solar Switch is unmistakable once you look under the unit.

Before You Start

Only proceed if the inverter is not displaying a fault or error condition. SMA’s manual is unambiguous: in the event of a fault, do not perform direct actions on the product and do not operate the DC load-break switch — rare fault conditions can even generate explosive gas mixtures or toxic substances inside the enclosure. If there is any error on the display, any burning smell, or any visible damage, the correct move is to switch off the AC breaker (if you are certain which one it is), keep people away from the unit, and call your installer or SMA service. Also, as with any brand: daylight hours only, dry conditions, and only touch breakers you are sure about.

Step-by-Step Restart Procedure

1. Confirm no fault is displayed. Check the display or the three diagnostic LEDs. This procedure is for a healthy-but-stuck unit (frozen display, monitoring dropout, unexplained standby) — not for clearing an active error.
2. Switch off the AC circuit breaker. Open the dedicated solar AC miniature circuit-breaker in your switchboard. SMA specifies that the AC side must always be disconnected before the DC side.
3. Open the DC circuit. On current models, turn the inverter’s DC load-break switch to OFF. On older models, pull out the Electronic Solar Switch. If your system has a separate external DC isolator, use that instead — SMA prefers the external device whenever one is fitted.
4. Wait for complete shutdown. Wait until the LEDs, the display, and any event numbers have stopped glowing entirely. Allow a full ten minutes: the DC-link capacitors hold charge long after the lights die, and SMA’s manuals note this discharge time explicitly.
5. Close the DC circuit. Turn the DC load-break switch back to ON (or reinsert the Electronic Solar Switch firmly).
6. Switch the AC breaker back on. Restore the grid supply.
7. Let the startup sequence finish. The Sunny Boy checks its internal parameters and the grid, then synchronises and begins feeding in. This takes a few minutes; do not interrupt it.

After the Restart

A successful restart ends with the inverter feeding power and the display showing normal production values. If the unit drops back into standby with sufficient sunlight, verify the basics: DC voltage from the array (older Sunny Boys need well over 100 V to leave standby — a single shaded string can hold the whole unit down), and grid voltage within range. If the Sunny Portal or SMA Energy app still shows the system offline while the inverter itself is generating, the issue is the communication interface (Speedwire/Webconnect module or your network), not the inverter.

When to Call a Professional

• Any fault or error message is displayed — SMA explicitly says not to operate the DC switch in this state; call a qualified person.
• The inverter will not start after a correct restart in full daylight.
• The AC breaker trips when switched back on, or trips repeatedly.
• Burning smells, unusual noises, visible damage, or heat damage on the enclosure.
• You need to change country data sets, grid parameters, or access installer menus — the country data set locks after ten feed-in hours and requires an SMA-issued access code.

Frequently Asked Questions

Why does my Sunny Boy sit in standby on a sunny day?

Standby with good sun usually means DC voltage is below the start threshold (shading, a failed string, or too few panels in series on older high-voltage models) or the grid is outside limits. Check the display’s measured values before restarting.

Can I restart the inverter from the app?

No. SMA provides no remote power-cycle function for the Sunny Boy — a restart means physically operating the AC breaker and DC switch in the documented order. Anyone promising a “remote reset” is describing a monitoring reboot, not an inverter restart.

How long should I wait with everything off?

Until every LED and the display are dark, plus a margin — ten minutes is the safe figure SMA’s documentation supports, because the internal capacitors need time to discharge fully.

Will a restart delete my yield data or settings?

No. Energy counters, country settings, and communication configuration survive a power cycle. Only a deliberate factory reset — an installer procedure — would clear settings.

Related Error Codes

• SMA Event 301 — grid fault event: what it means and how installers resolve it

Sources: SMA Sunny Boy SB 3.0–6.0 operating manual (commissioning/decommissioning: AC-before-DC disconnect order, capacitor discharge wait); SMA Sunny Boy installation manual (Electronic Solar Switch handling on TL-series models; fault-condition warning against operating the DC load-break switch).