Man I thought this discussion was over. There were so many that were quiet for a long time on this thread, and now they are not quiet.
Iwire, the drawings you have are great representations of the handle tie usage. However, in relation to this thread, and what has been argued over the last several pages, is that we are talking about field wired 240V and 120V loads. Your graphics are showing MWBCs feeding fixed, manufactured appliances or loads. Close, yes, but not what we are arguing. Rather we are argueing whether a 120V load can be combined with a 240/120V load, and what are the limitations or requirements or justifications for that?
I continue...
Jim Dungar, I got your point about the conductors, not the loads in your post. Take a look back through this thread again. I believe I had an installation example of a 240V baseboard Heater with an integral 120V duplex recept. The installation was in 12/3 cable, protected by (2) 20Amp breakers, Handletied. Now what happens when we plug in that 11Amp vacuum cleaner? OK, we plug in the vacuum somewhere else. What about that window A/C unit? Do we increase one of the breakers, to allow this new load. We might be able to legally put a 25Amp breaker in, along with the existing 20, and handle tie them. But that is still your convenience
duplex receptacle. What happens if we plug things in now? How about 30? 35? That's not going to work.
Maybe we should only allow this for fixed loads, not general or convenience loads? But neither the code rule nor the exception address anything like that.
Furthermore, if you want to address this like a 15 or 20Amp Branch Circuit, then you have something else to consider.
210.23 (A) (2) Utilization equipment fastened in place shall not exceed 50% of the branch circuit ampere rating. In my example
424.22(A) Fixed Electric Space Heating Equipment OCP refers you back to Art 210. This is getting scarrier by the minute
. Now that baseboard is limited to 10A, but that only allows for 10Amps for the convenience outlet. Yet because it is the only outlet on a 20A circuit, you must install a 20A device.
210.21(B)(1)
Now I am confusing myself while trying to confuse myself...
I think.
If we look at the original rule and its exceptions (210.4), nothing is mentioned about any of this. Are we to assume that it meant only fixed loads? Are we to assume nobody will plug a vacuum cleaner in? Are we to size the conductors to the largest load or combination of loads? That might be difficult, but could be done if loads are fixed loads.
Yet the blanket arguement that says that this style wiring is allowed, is hard for me to swallow on face value. There is a lot more to this type of circuit, if we try and wire this way and make it right, and my arguement is I could probably throw enough safety and workmanlike manner codes at this to make it wrong.
If all the planets were to line up, I could see this installation actually working. If the last one to leave could please turn out the light...