I have a dental lab in Europe and might want to move it to the USA. Some of the equipment rates as high as 4kW, and the the total maximum draw is 15kW for the whole lab. Can I wire a secondary breaker box in a building in the United States that is all 240V?
Electrical – wire a secondary 240V breaker box for lab equipment from Europe
240vcircuit breakerelectrical
Related Solutions
In the 2011 version of the National Electrical Code, there was Table 310.15(B)(7). This table was quite handy for determining the service conductor size. In the 2014 version, it looks like they've done away with this table. However, the long code trail that has replaced it, seems to basically say the same thing.
National Electrical Code 2011
Article 310 - Conductors for General Wiring
II. Installation
Typical services (in the US) are 100, 150, or 200 ampere (though 60 is common for older dwellings). Which means you'll be dealing with a possible range from 4 AWG copper to 2/0 copper (2 AWG al to 4/0 al). Which means you'll want a device that can accommodate conductors from about 0.3 in. diameter to about 0.7 in. diameter, if you want to cover the whole spectrum of possibilities.
The National Electrical Code used here in the US requires that equipment be listed, marked, or approved for the use. The requirement varies with the particular part of the electrical installation. Receptacles should be listed. However, that doesn't mean they have to be UL listed. The Canadians have the CSA, the Europeans have the CE, and I am sure in Asia they have something else that I can't remember. See here.
So, the issue with an inspector could be that the receptacle(s) you install is non-standard and they would probably disallow it for satisfying any requirements of the code. At least that is what I would do. But if you want to add non-standard receptacles in a house, there is nothing in the code to prevent it. For instance, if I wanted to wire my house with DC receptacles in places where I want to use DC equipment directly from a DC system. Or I want a 240 volt receptacle next to a window for a large plug-in AC unit.
One of the things the code requires is equipment with different voltages must have receptacles that are different enough so they are not interchangeable. So 120 volt equipment cannot possibly be plugged in to a 240 volt outlet.
So, it appears that you could satisfy the code requirements by adding an extra receptacle (not by replacing an existing one) with a euro-style plug. Also you need to make sure their equipment is rated for 240 volts or you will need a transformer to step it down to 230 or 220. Then you wire it like you would the aforementioned 240 volt receptacle. (Standard NM cable in the US contains wire rated for 600 volts so the voltage rating of the wire is not a problem.)
Good luck!
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Best Answer
Yes. The bigger problem is going to be if any of the equipment requires 50 Hz or is not approved here (e.g., Commercial U.L. or whatever code and insurance requires for a dental lab).