NTC 20D-20 Circuit Protection Power Thermistor 20ohms Power Supply Repair

NTC 20D-20 Power Thermistor 20Ω 250W – Mining PSU Inrush Current Protection

The NTC 20D-20 is a negative temperature coefficient thermistor with a cold resistance of 20Ω, rated at 250W, in a 20mm through-hole disc package. It serves as an inrush current limiter on the AC input stage of mining power supplies — at power-on, the 20Ω resistance limits the surge of current into the bulk capacitors, then self-heats and drops to near-zero resistance for normal operation. Operating range -40°C to +200°C, tolerance ±10%.

Why NTC Thermistors Fail in Mining PSUs

Every time the PSU is powered on, the NTC thermistor absorbs the inrush energy. In mining environments where PSUs cycle on and off frequently — during maintenance, power outages or rolling restarts — the cumulative thermal stress degrades the device. A failed NTC either cracks open (PSU won't start) or shorts (no inrush protection, stressing the bridge rectifier and bulk capacitors on every power cycle). Replacing a failed NTC is a low-cost repair that prevents cascading damage to more expensive components.

Replacement Procedure

Disconnect mains and discharge bulk capacitors. Locate the NTC on the input filter board near the AC inlet — it is a large disc component with two radial leads. Desolder both leads, remove the old thermistor and install the new NTC 20D-20 through the same holes. Solder, trim leads, reassemble and verify the PSU powers on normally with a controlled inrush.

NTC 20D-20 Thermistor Specifications

Related NTC Thermistors & PSU Protection Components

• MF72 10D15 NTC Thermistor – APW3 PSU Repair
• NTC 16D-20 Thermistor – PSU Repair Parts
• NTC 5D-15 Thermistor – PSU Repair
• NTC 8D-20 Power Thermistor – Innosilicon / Whatsminer PSU

Repairing mining PSU input stages? Contact us at contact@lys-sz.com for NTC thermistors, varistors and all input protection components.

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