Hashing From 120V Ac; Limiting Miner Power Draw; Reducing Hash Voltage And Hash Frequency; Remove Hash Boards - BITMAIN APW12 Manual

Hashing from 120V AC

Applying the modification steps in this guide to the APW12 PSU will enable it to power most
Bitmain X19 and X21 mining rigs from 120V AC. Care must be taken to not overload the 120V
AC circuit (circuit breaker, wiring, outlet, etc.). Be sure to consider the power requirements of the
mining equipment as well as all other electrical equipment on the same circuit. Also, keep in
mind that no electrical circuit should be run continuously at its maximum current rating. DOING
SO MAY RESULT IN CIRCUIT OVERLOAD AND/OR FIRE. For example, a 15 amp circuit
should never be burdened with more than 1440 watts (80% of its nominal rating) continuously. If
a modified APW12 power supply is running on a 15 amp circuit and drawing, for example, 1200
watts of power, only 1 mining rig should be powered from that circuit, and the sum total power
draw of all electrical equipment on that circuit (miner, computers, lights, etc.) should not exceed
1440 watts. See the "Limiting Miner Power Draw" section below for ways to ensure that the
miner does not pull more than 1440W.

Limiting Miner Power Draw

If powering a miner from a standard 120 volt, 15 amp outlet, care must be taken to limit the
miner's power draw to no more than 1440W MAX (1200W recommended). This section
describes two options for doing so. Employing one or a combination of these steps is required to
ensure a safe mining setup.

Reducing Hash Voltage and Hash Frequency

Generally, the lower the hash voltage (voltage present at the hash board's power terminals) and
hash frequency, the lower the miner's power draw will be to a certain extent; however, lowering
the hash voltage below the miner's minimum voltage requirement is not recommended. Doing
so may cause ASIC chips on the miner's hash boards to fail causing poor efficiency and/or an
increase in power consumption. Powering multiple hash boards from the same 120V outlet will
require BOTH running the hash boards at or close to their minimum hash voltage
(approximately 12V for most X19 variants, but 14V for some) AND underclocking significantly
with a hash frequency well below the stock hash frequency. The exact hash frequency that
should be targeted for limited power draw varies widely between X19 variants. It is
recommended to start low (50 - 100 MHz) and slowly work up until the desired power limit is
reached. If using an autotune feature, it is recommended to tune to the lowest possible power
target and then work up slowly until the desired power draw is reached. If the lowest autotune
setting will likely draw more than 1440 watts, either the autotune feature should not be used, or
one or more hash boards should be removed from the miner to limit the power draw.

Remove Hash Boards

Standard, off-the-shelf X19 miners come with 3 hash boards. Each individual hash board can
pull anywhere from as little as 350 W to as high as 2000 W based on the hash voltage, selected
hash frequency, and to a small degree, the temperature of the hash board's chips. Removing a
Document Revision 3
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2024-02-01