Antminer Z15 Pro Keeps Restarting — ERROR_POWER_LOST & Power Faults: Causes & Fix

Why a Z15 Pro restarts on its own

Bitmain rates the Z15 Pro at 840 KSol/s for about 2,780 W (±5%) — nearly twice the power of the original Z15. That makes the whole power path, from the wall circuit to the PSU to the hashboards, work much harder, and any weak link shows up as restarts, ERROR_POWER_LOST or boards dropping during start-up.

The tricky part is that the error usually appears on the power side even when the root cause is a hashboard. A board with a shorted voltage domain or a failing power component draws more current than it should when it powers up, the supply voltage sags, the control board sees an out-of-range voltage and the miner restarts. Swapping the PSU alone won't fix that, and a good replacement PSU can end up damaged as well.

Common Z15 Pro log messages

These are the lines we see most often on Z15 Pros that come in for restarting. Copy the full kernel log before rebooting — it is lost on power-cycle. Exact wording can vary slightly between firmware versions.

Four root causes, and how to tell them apart

Checks you can do yourself — in this order

1. Save the kernel log, then note which error appears just before each restart.
2. Check the site power: are other miners on the same circuit also restarting? Is the circuit loaded close to its limit? A Z15 Pro needs stable, correctly rated power.
3. Inspect the power cord and PSU connectors for heat discolouration or a loose fit. Never run a miner on a connector that shows burn marks.
4. Test with a known-good PSU of the correct model. If the restarts stop, the original PSU needs repair.
5. Isolate the hashboards: with the miner powered off, unplug one board at a time and run it. If it becomes stable without a particular board, that board is the cause.
6. Rule out firmware: if the log shows no power or chip errors, restore factory settings or recover the control board from an SD card.

Avoid power-cycling the miner over and over to "see if it settles". Repeated restarts on a board with a short can turn one failed part into several, and can damage a good PSU too.

How we repair a Z15 Pro that keeps restarting

We test the whole power path, not just the part that reported the error. Hashboards go on a test fixture where each voltage domain is checked for shorts before full power is applied, and thermal imaging under load shows the chip or power component that is drawing too much current. Failed parts are replaced at the chip level, and the board runs a full-load burn-in before it goes back. If the power supply was damaged along the way, we repair Bitmain APW-series power supplies too — see our Antminer PSU repair service.

A solo miner is typically repaired in 1–3 days, and small batches within 1–2 weeks. If your Z15 Pro also runs hot or throws "Temp NG" errors, read our Z15 Pro overheating guide. Boards reading zero hashrate instead? See Z15 zero hashrate and missing chips. Full service details are on our Antminer Z15 Pro repair page.

Frequently asked questions

Why does my Antminer Z15 Pro keep restarting?

The four usual causes are unstable site power, a weak or failing power supply, a control board or firmware fault, and a damaged hashboard — for example a short — that pulls the supply voltage down when the board powers up. Overheating can also trigger protective shutdowns. The kernel log tells you which one to look at first.

What does ERROR_POWER_LOST mean on a Z15 Pro?

It means the control board detected a power problem — the supply voltage rose, dropped or could not be read correctly — and stopped the miner. It points at the power path, but the cause can be the site circuit, the PSU, the power leads or a hashboard overloading the supply.

How do I know if it's the PSU or a hashboard?

Test with a known-good PSU of the correct model. If the restarts stop, the original PSU is the problem. If they continue, unplug one hashboard at a time: if the miner becomes stable with a particular board removed, that board is pulling the supply down and needs repair.

Can a firmware reflash fix a Z15 Pro that keeps rebooting?

Sometimes. If the restarts come from a corrupted configuration or firmware, restoring factory settings or recovering the control board from an SD card can fix it. If the log shows power or chip errors, firmware will not fix the underlying hardware fault.

Do you repair Z15 Pro power supplies as well as hashboards?

Yes. We repair Z15 Pro hashboards at the chip level and also repair Bitmain APW-series power supplies, so the whole power path can be fixed in one place.