celtic, Here is something from 220.14(I)describing your equipment wording.Also in resi,yoke refers to devices mainly,but can also be a double pole stat such as your unit heater if it was 220,a contactor,a disconnect,a panel box.anything that is multiwired with a common link needs to have a common means of disc.
Here is 220.14(I)
(I) Receptacle Outlets Except as covered in 220.14(J) and (K), receptacle outlets shall be calculated at not less than 180 volt-amperes for each single or for each multiple receptacle on one yoke. A single piece of equipment consisting of a multiple receptacle comprised of four or more receptacles shall be calculated at not less than 90 volt-amperes per receptacle. This provision shall not be applicable to the receptacle outlets specified in 210.11(C)(1) and (C)(2).
Rick