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Cryptoccurrency miners and related equipment are not consumer appliances!

The operation of high-power, high-voltage electrical equipment such as miners, PSUs and PDUs creates risks of fire or electrocution. These risks can be reduced by proper operation, but not completely eliminated. Here are a few tips to help you manage mining hazards.

The simplest solution is to host your miners in a professionally designed blockchain data center. Many people however prefer to house their miners in a location under their control - often their home, garage, a small outbuilding or light commercial space. There are many safety considerations involved if you wish to mine on your own, and we address some of them in our FAQs. Four items however deserve special mention:

  1. Miner placement

  2. Do not mine on 110V

  3. Get an electrician - and explain them the exact nature of what you do

  4. Contact your electric company and verify available power

Let's begin with the most obvious safety recommendation.

 

1) Place miners, power supplies, and power distribution equipment:

  • On non-flammable surfaces

  • Away from flammable items such as curtains, bedding, paper, solvents...etc.

  • In a location not accessible to pets and children

You'd be suprised to see how often this "duh"advice is not followed in practice. Usually, this is the result of being rushed or seeking an expedient solution. For example - a miner placed under the bed to reduce noise in a college dorm room. Or a mining rack in a garage few feet away from cans of paint thinner and whatnot - with an eager dog around. Please do not do this. The typical bitcoin miner is equivalent to a floor heater, and should be treated with similar caution. Now, onto something less obvious.

2) Do not plug miners on "regular" 110 Volt wall outlets.

"What !?!? Where should I plug them then ?"

Answer: Plug your miners in a dedicated "220 Volt" circuit that has sufficient rated capacity to supply the electrical current required by the mining load. The vast majority of households and light commercial spaces in the Americas have "220V" at the electrical panel - it's just that this voltage is not normally provided in the regular wall outlets you know.

This advice is no joke. To understand how serious it is, we need to delve into the concepts of electrical power and circuit rating. You should really let an electrician do this in practice (see below) but the text will help you understand why.

The typical ASIC miner draws up to 1400 Watt of electrical power to run. Now, we have "Power (Watts) = Voltage (V) x Current (Amps)". If your voltage is "110 Volts" (in practice, ranging from ~100-130V depending on location), the currents in your wiring will range from 11 to 14 Amps for a single miner. It's the current (not voltage) that causes wiring to heat up.

You might say - "no problem, I have a 15 amp circuit" (common in many homes). The problem is that the "15 amp" rating you see on the breaker is NOT the current that this circuit can supply safely on a continous 24/7 basis. That "15 amp" rating is the current that will trigger the breaker provided the latter is not subjected to excessive heat above its rated operating temperature.

The actual maximum current an electrical circuit can deliver on a continuous basis is rather complex to calculate. It depends on the details of how the circuit is built, and on the environment where it runs. An electrician should be able to calculate how much current you can draw for mining. Rest assured however that this current will be less than the value printed on the breaker - sometimes much less. A residential 15A circuit built with NMC/Romex cable running in a hot wall filled with thermal insulation may be unable to carry more than 8-10 amps on a continuous basis.

 

Exceeding this current will cause the wiring to overheat to the point where the insulation will start charring. If the insulation is damaged, the likelihood of a short circuit somewhere inside the wall increases. The breakers normally trigger when a short occurs. But in this case, the breaker is likely to have overheated too, and it's ability to trigger is compromised. The result - an electrical fire inside the wall or at a similar "out of sight" location.

 

This holds true even for a single miner. The typical 110V wall outlet circuit has many gangs of outlets, and it's likely other electrical loads will end up being plugged into it - thereby making the problem worse.

 

Do yourself and your neighbours a favor - if you're serious about mining, get an electrician to install a few 220V outlets on dedicated circuits from your electrical panel. It's a relatively modest expense, and is money well spent. For the same amount of power, the current on 220V is half of what it would be on 110V. This allows a more robust and cost-effective circuit construction, with less risk of overheating.

3) Hire a licensed electrician - and explain what you plan to do

Continuous load. High temperature. Temperature correction factors. Overcurrent protection.  Temperature rating of components. Enclosures and raceway selection. These are some key words you'll need to discuss with your electrician.

It's not enough to switch to 220V and think all is well. Your mining circuits carry less current than they would have otherwise, but still need to be properly sized for the amount of power they will serve.

Many miners are technically savvy enough to google cable ampacities and the "80% rule". The result is people jumping to conclusions such as "Hey, I can draw up to 24 amps from this outlet that has a 30A breaker on the other end". Sadly, this is wrong. Such simple formulas are a recipe for disaster.

The correct procedures for sizing a circuit are described across several articles of the National Electrical Code. They are relatively complex and take into account the operating environment. A licensed electrician should be able to determine the right circuit size and design. This is the information you need to provide them:

 

  • The load is continuous 24/7 and has basically 100% duty cycle at constant power

  • The total power your mining setup requires. In estimating this, you should factor power supply losses, and the prospect of having more powerful miners at some point in the future. A figure of 1,600 Watts per ASIC miner is a good starting assumption you need to validate against the actual miners you plan to install. GPU mining rigs also draw considerable power - much more than gaming PCs. Consider 150 to 200 Watts per card in your GPU rig as a starting point, and verify it against the actual for your particular GPUs.

  • That part of the mining area will get HOT. The temperatures on the exhaust side of a large mining rig can exceed 130 degrees F. The current-carrying capacity of a circuit that is exposed to the hot side can be much less than the capacity of the same circuit at normal building temperatures. If you don't tell this important detail to your electrician, they might size the circuit assuming their everyday practice - and you'll end up with far less capacity than you think.

 

4) Inform your power company

The amount of electrical power available at your panel entrance is not infinite. In fact, a cryptocurrency mine as small as a 10-15 miners may overload the power company equipment in many residential or light commercial areas.

The consequences of overloading utillity distribution equipment can be catastrophic. An overloaded low-voltage  transformer (the "cans" on top of utility poles or the "green boxes" by the curb) can cause a large electrical fire and serious damages. In many locations, utillity transformers, meters, and conductors are sized for typical household demand, and are not at all adequate to power multitudes of miners.

 If you plan to grow your mine beyond a handful of miners, please do call your power company and let them know the estimated power draw from your operation. Talk to "engineering", not "billing", and tell them this is a continuous load. As an initial guideline, consider 15 kW of power per x10 Antminer S9.

The power company will tell you how much power is available at your panel service entrance, and will have recommendations if this is not enough for your needs. You need to go through this process whatever the possible outcome may be. The worst possible arrangement is to ignore the problem and try drawing more power than the utility can safely deliver.

There are many other technical aspects to building a successful cryptocurrency mine. We present many of them in our technical publications, white papers, and FAQs. The four items above are however so important they deserve a section on their own. Please heed them carefully to help you reduce mining hazards.