Reading Breaker Headroom for 0.08 TH/s Expansions

A 400 A service does not offer 400 A for new mining load. Concurrent building demand — guesthouse HVAC, commercial kitchens, farm chillers — shares the same meter. On Jeju tourist corridors, July evening load can consume 35% of service capacity before miners ramp.

Step-by-Step Headroom

1. Export meter interval data if your utility provides it; otherwise sample peak amps with a clamp meter during evening peak for one week.
2. Subtract measured peak from 80% of service rating (leave NEC-style margin; Korean installs follow similar practice on industrial panels).
3. Convert remaining amps to watts at your measured voltage — use 220 V line-to-line averages, not nameplate 230 V.
4. Divide by projected watts per TH for your shortlist units. That is hash you can add without panel work.

PDU Layer

Headroom at the main breaker does not guarantee PDU branch capacity. Map each branch breaker to rack positions before assuming a open PDU slot means available load.

When to Plan Sub-Panels Early

If headroom math leaves less than 0.05 TH/s worth of watts after margin, order panel work before hardware. Lead times for switchgear beat ASIC shipping only if you start early.

Field Example

Jeju City warehouse: 320 A service, 198 A peak non-mining, 245 A peak with current 0.06 TH/s fleet. After margin, roughly 55 A remained — enough for one small batch, not the three racks the distributor proposed. Staged plan saved a trip fault during a heatwave concert weekend.