Thermal derating means the inverter lowers its own output power on purpose when ambient or internal temperatures get high. It is a protection feature, not a fault: by limiting maximum output, the inverter keeps sensitive parts such as IGBTs and filter components within safe limits and avoids shutting down completely. Many string inverter manuals state that output starts to derate once ambient temperature passes 45°C (113°F), and each manual gives a derating curve for its model. In one central inverter example, full output holds up to 35 degrees Celsius ambient, and the unit still delivers roughly 90% of rated power up to about 50 degrees before it cuts output sharply. At high altitude the thinner air cools less well, so derating starts earlier; one manual specifies derating above 2000 m. Derating can also be triggered by internal temperature sensors on power stacks and controller boards, not only by ambient temperature. If logs show overtemperature derating while ambient temperature is normal, check the inverter cooling: clean filters, confirm the fans run, and look for poor ventilation or direct sun on the unit.
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explainsc1 drafted · lead Inverter power derating
Adverse environmental conditions such as high ambient temperature are one listed cause of inverter power reduction.
sec=h1 h=29bb5fd6708csec=3.7 h=905d4a97525asec=3.7 h=822f4c06dd80sec=h53 h=f6edd1c7148frelated_toDerating is a controlled performance reduction, usually depending on component temperatures, used to avoid a full shutdown.
sec=h632 h=f76b798a6e57sec=h1 h=29bb5fd6708cverified by: review-workflowverified on: 2026-10-24
c3 drafted · lead Inverter cooling
Derating takes over when the cooling system cannot remove enough heat from internal components.
sec=h1 h=29bb5fd6708cc4 drafted · lead Inverter Overheating
tbl=6.r28 h=36ac9eb68a94sec=h1 h=63d12e4af068c5 drafted · lead High operating temperature
Scope: products CPS SCH350KTL-DO/US-800, Solectria PVI 20/25TL-480-R, CPS SCA50-60KTL-DO/US-480
Manuals state output begins to derate when ambient exceeds 45°C (113°F).
sec=9.2.3 h=2bdbfd303a55sec=h178 h=c28885eae849sec=10.3.1 h=1391406b53e3sec=h53 h=f6edd1c7148fc6 drafted · lead High altitude
Thinner air cools less well, so maximum output is limited earlier and more steeply at higher sites.
sec=h1 h=29bb5fd6708ctbl=33.r3 h=bc3c13e7aad2sec=h138 h=95e3472bee58sec=h147 h=12f53f4c5d91c7 drafted · lead Fan failure
Fan failure is listed as a derating cause; checking fan operation is a recommended step for overtemperature derating.
sec=3.7 h=822f4c06dd80sec=h1 h=63d12e4af068c8 drafted · lead Clear ventilation blockage
Derating from internal overtemperature at non-critical ambient may indicate cooling filters need cleaning.
sec=h1 h=29bb5fd6708csec=h1 h=63d12e4af068review note: support check: partial - Transcript says internal overtemperature with normal ambient suggests cooling issues and cleaning filters; 'clear ventilation blockage' is only loosely matched, though ventilation check is mentioned.
c9 drafted · lead Ambient temperature check
sec=h1 h=63d12e4af068c10 drafted · lead Temperature-linked output derating
sec=h1 h=29bb5fd6708csec=h147 h=b928486f8520explains c1