240 Volt from Service Panel A to Panel B?

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Occasional Visitor
Fair point.
Im just overpy cautious because I DO understand the risks. I’m doing my best to understand to mitigate them.


Part of the Furniture


Very Senior Member
You should also check your local building code for requirements.

Also note that your insurance company should also potentially be consulted. To be covered, they may require the work be done, or at least inspected, by a licensed professional.

Replacing a light fixture or even adding an outlet are pretty basic tasks, but adding a sub panel is likely a different story. There are likely restrictions in place to limit the load on your primary panel too. I'd be very concerned about overtaxing some part of the infrastructure that you are not aware of or currently considering without talking to a licensed individual.


Part of the Furniture
I'm looking at running an additional breaker box in my basement for my unraid, ubiquiti and other gear in a comm. closet of sorts. Eventually this will turn into my office.

I want to run 240 Volt power for my gear. DO I need to run 240 from one side to the other, or can I run 120 and then draw 240 on the other side? Does anyone have any links on how this would be done?

Edit Added for detail:

I'm doing a bit of my own work and I've made sure I have complied with gauge and safety requirements. My second breaker box is mounted on an external concrete wall.

I have 50' of untrimmed 6/3 wire (got it off the shelf for $168, so it was cheaper than the 6/2 stuff.) This is in metal flex conduit and strung through my basement trusses. It's a direct run from Panel A to Panel B.

I only need about 50-60 amps of server at location B. I'm using SIEMENS gear and have 12/2 and 12/3 in metal flex to run behind my insulation on the concrete wall.

What I'm trying to figure out is how I get 240 Volts to Panel B.

DO I run a single 50 AMP breaker for the main at panel B and use 120 and then draw 240? This seems wrong.

DO I instead install the joined, dual pole 50 amp breaker on one of the child slots and then run/mark that as the main breaker? This makes the most sense, but I'm an IT guy trying to learn power, not an EE or Electrician (though I'm thinking about going for an EE.)
There are many YouTube videos on how to install a sub panel correctly and to code. If you don't understand the videos and are not comfortable working with electricity hire an electrician. To install the sub panel and have 240 V, at least in the USA, you will need a cable between the main panel and the sub panel with three current carrying conductors plus an additional grounding conductor.


Part of the Furniture
And it will matter if the cables for the subpanel are copper, aluminum, (or something else).

Always use larger cables than required by code (you'll never regret the few dollars extra that you'll only pay once for).

For example, for a 60A Panel, you'll need either 4 gauge or 3 gauge (temperature/wire material and length of run dependent).

Here's a quick search for you.

20, 30, 40, 50, 60 amp wire & breaker chart: What size do I need (atlanticaspiration.com)

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