AC Trips, Won't Start, or Shuts Down on Solar/UPS (Voltage Issues)

Key Takeaways

• The most likely cause is the AC's high startup current exceeding the inverter's surge capacity.
• The first check is your inverter's display for error codes and its AC input voltage range setting.
• Always ensure the inverter's rated output power matches or exceeds the AC's requirements, accounting for surge.
• Never attempt to open an AC unit or inverter without isolating all power sources and waiting for capacitor discharge.

Why does my AC trip or not start on solar/UPS power?

Your air conditioner may trip, fail to start, or shut down when running on solar or UPS power primarily due to the inverter's inability to handle the AC unit's power demands, especially during startup. The most common cause is the AC's high inrush current exceeding the inverter's surge capacity, or voltage instability from the inverter. The first thing to check is your inverter's display for any error codes and verify its AC input voltage range settings.

Diagnosis section

1. Check the inverter's display for error codes.

• • If you see an overload or overcurrent code (e.g., Axpert/Growatt code 07 or 51, Deye code F19): This indicates the inverter detected a load exceeding its capacity. For Axpert VM III and Growatt SPF ES inverters, a "Fault code 07" means "The inverter is overload 110% and time is up." A "Fault code 51" means "Over current or surge." For Deye SUN-SG03LP1-EU inverters, "F19" indicates "AC over current fault of hardware." This often happens during the AC's compressor startup.
  • If you see a voltage or frequency error code (e.g., Deye codes F23, F25, F26): "F23" means "AC line low voltage," "F25" means "AC over frequency," and "F26" means "AC lower frequency." These indicate the inverter's output voltage or frequency is outside acceptable limits, which can prevent the AC from operating correctly.
  • If no error code is displayed: The inverter might be shutting down due to a momentary surge it cannot handle, or the AC unit itself is detecting an issue.

2. Verify the inverter's AC input voltage range setting.

• • For Axpert VM III and Growatt SPF ES inverters: Check Program 03. If set to "UPS" mode, the acceptable AC input voltage range is "170-280VAC". If set to "Appliances" mode, the range is wider at "90-280VAC" (Axpert) or "90~280VAC" (Growatt). A tighter "UPS" voltage window can cause the inverter to switch to battery power or trip more easily if the grid or generator voltage fluctuates, even slightly.
  • For Deye SUN-SG03LP1-EU inverters: While there isn't a direct "Appliances" or "UPS" mode, ensure the grid voltage settings are appropriate for your supply. The manual provides default "Grid Vol High" (265.0V) and "Grid Vol Low" (185.0V) settings.

3. Check the AC unit's display for error codes (e.g., Gree Pular R32).

• • If you see an E5 code: For a Gree Pular R32, "E5" means "Overcurrent protection." The manual states this can be due to "Supply voltage is unstable," "Supply voltage is too low and load is too high," or "Evaporator is dirty." This directly points to an issue with the power supply from the inverter or the AC's internal load.
  • If you see PH or PL codes: For a Gree Pular R32, "PH" indicates "Voltage for DC bus-bar is too high," and "PL" indicates "Voltage of DC bus-bar is too low." These suggest the AC unit is detecting an out-of-spec voltage from the inverter. The fix direction for PH states: "Measure the voltage of position L and N on wiring board (XT), if the voltage is higher than 265VAC, turn on the unit after the supply voltage is increased to the normal range." For PL: "Measure the voltage of position L and N on wiring board (XT), if the voltage is higher than 150VAC, turn on the unit after the supply voltage is increased to the normal range."
  • If you see U3 code: For a Gree Pular R32, "U3" indicates "Malfunction of voltage dropping for DC busbar," with "Supply voltage is unstable" as a likely cause.

4. Observe the AC unit's restart behavior.

• • If the AC attempts to start, then immediately shuts down or trips the inverter: This is a classic sign of high inrush current. Air conditioners "are required at least 2~3 minutes to restart because it’s required to have enough time to balance refrigerant gas inside of circuits." If the inverter cannot sustain the initial surge for this period, it will trip.

5. Compare the AC unit's power requirements with the inverter's capacity.

• • Locate the AC unit's rated power (often on a sticker on the outdoor unit).
  • Compare this to your inverter's "Rated Output Power" and "Surge Capacity." For example, an Axpert VM III 5KW inverter has a rated output of "5KVA/5KW" and a surge capacity of "2 rated power" for "5 seconds". A Deye SUN-5K-SG03LP1-EU has a "5000W" rated AC output power and a "6500W" peak power (off grid). A Growatt SPF 5000 ES has a rated output of "5KVA/5KW" and a surge capacity of "2 rated power" for "5 seconds". Ensure your inverter can handle both the continuous running load and the much higher, but brief, startup surge.

Cause/fix table section

Inverter and AC Unit Checks

When an AC unit struggles to operate on solar or UPS power, the problem can stem from either the inverter's capabilities or the AC unit's specific requirements.

Inverter-Side Checks

• Capacity and Surge Power: Ensure your inverter's "Rated Output Power" is sufficient for the AC unit's continuous running load. More critically, verify the inverter's "Surge Capacity" can handle the AC's startup current. For example, Axpert VM III and Growatt SPF ES inverters offer a "2* rated power" surge for "5 seconds". A Deye SUN-SG03LP1-EU inverter has a "Peak Power (off grid)" rating (e.g., "6500W" for the SUN-5K-SG03LP1-EU model). If the AC's startup current exceeds this, even briefly, the inverter will trip.
• AC Output Voltage and Frequency Stability: Inverters like the Axpert VM III and Growatt SPF ES regulate AC output voltage to "230Vac± 5%" and frequency to "50Hz". Deye SUN-SG03LP1-EU inverters output "220/230 (single phase)" at "50/60Hz". Fluctuations outside these tolerances can cause the AC unit to shut down or display voltage-related errors.
• AC Input Voltage Range Setting: For Axpert VM III and Growatt SPF ES inverters, Program 03 allows you to configure the acceptable AC input voltage range. "Appliances" mode (default) provides a wider range of "90-280VAC" (Axpert) or "90~280VAC" (Growatt). "UPS" mode tightens this to "170-280VAC" (Axpert) or "170~280VAC" (Growatt). If your grid or generator supply is unstable, the "UPS" setting can cause frequent transfers to battery or inverter trips.
• Breaker Sizing: Ensure the AC breaker connected to the inverter's output is correctly sized. For Axpert VM III, recommended AC breakers are "16A for 1.5KW", "32A for 3KW", and "50A for 5KW". For Deye SUN-SG03LP1-EU, the recommended AC breaker for backup load is "32A" for 3.6KW and "40A" for 5KW/6KW models. For Growatt SPF ES, "40A for SPF 3500 ES" and "50A for SPF 5000 ES" are recommended. An undersized breaker will trip prematurely.

AC Unit-Side Checks

• Startup Characteristics: Air conditioners, particularly inverter models, have a high initial current draw when the compressor starts. This "inrush current" can be several times the running current. The AC unit also has a built-in "2~3 minutes to restart" delay after power interruptions to balance refrigerant gas.
• Error Codes: The Gree Pular R32 air conditioner provides specific error codes. "E5 Overcurrent protection" is a common indication of power supply issues. "PH Voltage for DC bus-bar is too high" and "PL Voltage of DC bus-bar is too low" directly point to the inverter's output voltage being out of the AC's acceptable range. "U3 Malfunction of voltage dropping for DC busbar" also suggests an unstable supply.
• Dedicated Circuitry: The Gree Pular manual states, "The air condition must apply specialized circuit and prohibit share the same circuit with other appliances." This emphasizes the need for a dedicated, stable power supply.

Safety: Working with AC and Inverter Systems

Working with AC units and solar inverters involves significant electrical hazards. "All electric work must be performed by a licensed technician according to local regulations and the instructions given in this manual."

• Mains Voltage Hazard: The indoor unit's terminal block operates at 230 V. The outdoor unit contains capacitors that can hold a dangerous charge even after power is disconnected.
• Isolation Procedure: Before attempting any inspection or work near wiring or internal components, always:

1. 1. Turn off all power sources: This includes the main AC breaker, the inverter's AC output breaker, and the DC breaker from the battery bank and solar panels.
   2. Verify isolation: Use a multimeter to confirm that no voltage is present at the terminals you intend to work on.
   3. Wait for discharge: Allow the manual's specified capacitor discharge time (typically 5-10 minutes for inverters and outdoor AC units) before touching any internal components.

• Grounding: "Have the unit adequately grounded. The grounding wire can't be used for other purposes." Improper grounding can lead to electric shock.
• Wiring Integrity: "Unstable power supply or incorrect wiring may result in electric shock, fire hazard or malfunction." Ensure all connections are tight and correctly wired. "If power cord or connection wire is broken, it must be replaced by a qualified person."
• Air Switch: For AC units without a plug, "an air switch must be installed in the circuit. The air switch should be all-pole parting and the contact parting distance should be more than 3mm."

When to call a technician instead

While basic troubleshooting can identify common issues, many problems related to AC units and inverters require professional expertise. You should call a qualified technician if:

• You are unsure about any diagnostic step or electrical measurement.
• The problem involves opening the inverter or AC unit housing, as this is typically "authorised-service work" and can void warranties.
• You are dealing with persistent error codes that do not clear after basic troubleshooting.
• The issue involves refrigerant leaks (E3 code on Gree Pular) or compressor problems (E4 code).
• You suspect internal component failure in either the inverter or the AC unit.
• The problem requires changes to internal inverter settings beyond basic user-configurable options.
• "Unstable power supply or incorrect wiring may result in electric shock,fire hazard or malfunction." If you suspect either of these, contact a professional immediately.

Attempting repairs or modifications beyond your skill level can lead to further damage, personal injury, or void your product warranties.