I am having my main circuit breaker panel replaced (by a licensed electrician) and he told me I can run new circuits for him to hook up to the new panel. Is there any benefit to running 240v circuits for computers, network equipment, other devices that support it?
I would probably put a 120v outlet next to any 240v just for convenience (I was thinking on opposite sides of each stud.
Best Answer
There's no need to do this for computers/networking gear/...
While the switching power supplies used in IT equipment are slightly more efficient when running on 240V vs when they are running on 120V, this efficiency difference is generally small enough that it can be disregarded as a practical matter. As a result, I would simply provision 120V/20A circuits for equipment closets, office spaces, and the likes.
HOWEVER: there are spaces where this is a good idea
The above, though, is not universal advice in the sense that it is specific to IT equipment. Shop spaces where fixed power tools are used, such as woodshops or metalshops, benefit greatly from having both 120V (NEMA 5) and 240V (NEMA 6) receptacles present; this is also something that's not beyond reason for a well-appointed kitchen, although most of the kitchen appliances that can take advantage of this are commercial types.
In any case, you don't need to pull extra circuits to have both 120V and 240V together...
One benefit of the North American split-phase system over pure single-phase distribution is the ability to use multi-wire branch circuits to provide twice the current/power sourcing capability of a single branch circuit while using 3/4ths the copper and generating half the heat compared to having two independent branch circuits, something that is especially useful when mains wiring is done using individual wires in conduit (vs. prefabricated cables).
While these are normally only used with 120V receptacles and fixtures connected line-to-neutral, the use of a common-trip two-pole breaker (which is the normal way one wires these any more) allows a mixture of 120V and 240V loads/receptacles on the same branch circuit, as per NEC 240.4(C) Exception 2:
This also permits the use of NEMA 5/6 combination duplex receptacles, such as the Leviton 5844. These provide access to both 120 and 240V on the same yoke when fed by a properly wired multi-wire branch circuit, without having to resort to a dodgy adapter.
...but this comes with some caveats
However, the requirement for a two-pole common-trip breaker does pose a few caveats when arc and/or ground-fault protection is required. First and foremost, if you have a GE panel, you cannot use this strategy on any circuit where arc-fault protection is required, as the current (Mod 3) GE AFCI breakers are not available in a two-pole common-trip configuration, only single-pole units that can be handle-tied for 120V-only or 240V-only service. (If you can obtain a Mod 2 GE CAFCI used, you can do it that way, but those are likely to be relatively thin on the ground.)
Furthermore, in spaces where both arc and ground fault protection is required (right now, only kitchens, laundry rooms, and bathrooms), you're forced to have a 2-pole arc-fault breaker in series with a 2-pole ground-fault breaker to protect these circuits, as 2-pole dual function (AF/GF) breakers are not available at this point in time, and appear unlikely to become available any time soon. For an individual circuit, this can be accomplished using an arc fault breaker in the panel and a "spa panel" in-line with the homerun to provide the GFCI protection; however, if you are wiring several circuits this way, it's better to use a split-bus (albeit not rule-of-six) panel (such as a Siemens generator panel) to provide this series configuration, with a GFCI breaker replacing the normal utility feed breaker to the "generator" section of the panel and AFCI breakers in the "generator" section feeding the individual branch circuits.