Power Distribution for Half-Rack Shelves
Why voltage sag on a shared circuit costs more hash-rate than a marginal ASIC chip.
Half-rack shelves tempt operators to pack units tightly and feed them all from a single PDU on one circuit. It works until it does not — and when it fails, hash-rate drops across every unit on that shelf simultaneously.
PDU Placement
Mount the PDU in the bottom 1–2 U of the shelf, not mid-rack. Lower placement keeps power cables shorter and reduces the cable bundle pressed against rear exhaust grilles. Use right-angle C13/C14 connectors where the rack depth is tight.
Circuit Loading Rules
Our practice for compact facilities:
- One 20A circuit per half-rack shelf for up to four units in the 0.05–0.20 TH/s class
- Never exceed 80% of circuit rated capacity for continuous mining load
- Log voltage at the PDU under full shelf load — sustained readings below 220 V (on 230 V service) indicate undersized wiring or overloaded circuits
Cable Routing
- Route power cables along the side cable channel, not across the rear grille
- Separate power and network cables where possible to reduce electromagnetic interference on long runs
- Label each C13 lead with the U-position it feeds — essential for troubleshooting throttling on a single unit
Signs of Power Problems
- Hash-rate fluctuation synchronized across all units on one shelf
- PSU fan ramping on multiple units at the same time of day (often correlates with building HVAC load)
- Warm PDU body or discoloured outlet faces
A power and thermal audit includes a full PDU load spreadsheet and voltage log under sustained shelf load.