To confirm your miner is grounded, run two checks: a power-off earth-continuity test that proves the chassis is bonded to your building’s protective earth, and a running touch-voltage test that catches stray AC leaking onto the case. A correctly earthed miner shows near-zero resistance from its aluminum shell to your outlet’s ground pin, and essentially 0 V AC between the shell and a known ground while it runs. Anything else means the chassis is floating or leaking — a shock and equipment risk you fix before the unit stays on the shelf.
Why grounding matters on an ASIC miner
An ASIC miner is a metal box carrying a switch-mode power supply fed from mains. The chassis has to be tied to protective earth (PE) so that if any live conductor ever contacts the case, fault current runs to ground and trips the breaker instead of sitting on the shell waiting for your hand. Grounding also gives switching noise a return path, which keeps stray potential off the data and control lines that talk to the hashboards.
The real danger inside the shell is not the low-voltage DC bus. The bolted copper bus-bar on an S17/S19/S21 (or the per-board power connectors on an S9) runs at only 8–21 V DC — not a shock hazard. What bites you is the mains and PFC section of the PSU, where the bulk capacitors hold roughly 410–420 V even after you unplug it. That is exactly why the chassis bond has to be intact: a single insulation failure inside that sealed brick can energize the whole case.
What you need
- A digital multimeter with continuity/resistance (Ω) and AC-volts modes.
- A known-good ground reference — the ground pin of the same outlet the miner plugs into, or a proven building-ground point.
- Insulated gloves and dry footing; treat the unit as live until proven otherwise.
Test 1 — Earth continuity (power off, do this first)
This is the primary test. It proves the case is actually bonded to earth before you rely on any live reading.
- Power down the miner and unplug the PSU from mains. Leave it disconnected for a few minutes so the PFC capacitors bleed down.
- Isolate the miner from any metal shelf or rack — set it on a non-conductive surface so a bench short doesn’t fake a good reading.
- Set the multimeter to continuity or the lowest resistance (Ω) range. Touch the two probes together first and note the meter’s own lead resistance (typically 0.1–0.5 Ω).
- Put one probe on bare, unpainted metal of the miner’s aluminum chassis (a heatsink fin, a screw head, or the fan guard) and the other on the ground pin of the power cord’s IEC plug or the wall outlet’s ground.
- A healthy bond reads a near-zero, low single-digit ohms (lead resistance plus a fraction). An open circuit or a reading in the hundreds/thousands of ohms means the chassis is not earthed — stop and fix the ground path before powering up.
Test 2 — Touch voltage (miner running)
This catches leakage that only shows up under load, after the continuity test has confirmed a bond exists.
- Confirm the miner is not touching any metal shelf or the rack — contact through the rack can mask a floating chassis and give a false pass.
- Set the meter to AC volts, on a range that covers your mains (200 V AC or auto-range; North-American service is 120/240 V).
- With the miner running, put one probe on the aluminum chassis and the other on your known ground point.
- A properly earthed miner reads essentially 0 V AC. A reading of a volt or more means AC is leaking onto the shell — the earth bond is missing, high-resistance, or the PSU is leaking. Investigate before the unit runs unattended.
- Repeat with one probe on the chassis and the other on the metal frame of the Ethernet jack. That frame should sit at chassis potential; a voltage difference there points to a control-board mounting or shield-bond fault. Keep the jack frame clear of the control-board panel while you measure so contact doesn’t skew the reading.
If the miner is floating or leaking
- Prove the outlet first. Many “ungrounded miner” calls are actually an ungrounded outlet or a cheater adapter. Test the receptacle with a plug-in tester; a two-prong-to-three adapter or a lifted ground defeats the whole chain.
- Inspect the power cord and IEC socket. A broken ground conductor or a bent/pushed-back ground pin in the C13/C19 connector opens the bond even when everything looks plugged in.
- Check chassis screws and the PSU mounting. The bond relies on the PSU ground reaching the sheet-metal. Paint, corrosion, or a missing screw under a lug can float a panel. Clean to bare metal and re-torque.
- Suspect the PSU. A supply that leaks AC to its own case will push the whole chassis up even with a good building ground. If the leak persists with a confirmed earth path, the PSU is the fault — pull it from service.
Common mistakes
- Skipping the power-off continuity test and trusting a live 0 V reading — a coincidental shelf contact can fake it.
- Probing painted or anodized surfaces; the meter reads the coating, not the metal. Always find bare metal.
- Grounding a miner to a water pipe or a random rack instead of the electrical system’s protective earth.
- Assuming a whole hashcenter shares one ground — each circuit and each unit’s cord must be verified on its own.
Escalation
Grounding is where amateur wiring becomes a fire and shock problem. If the outlet itself is ungrounded, if continuity stays open after cord and chassis checks, or if you can’t localize a persistent leak, stop and bring in a licensed electrician to correct the branch circuit and bonding. Earthing the rack correctly is cheaper than replacing a hashboard — or worse.
Related: Cross-check symptoms with the ASIC fault finder, confirm your model’s power and earthing details in the manuals library, and read up on the underlying terms in the ground fault and leakage current glossary entries. When a leak traces back to a failing supply or bonding you can’t clear, start a repair and let the bench sort it.
