I have a double pole 20A breaker feeding a 120V MWBC with 12/3 with ground, romex that goes up three levels to two separate 120V duplex GFCI receptacles with common neutral.
I want to have both 120V and 220V small appliances. Wanting to add a 220V 6 amp coffee maker to two small 120V appliances. This is not a kitchen, but indoors, off of a top deck. The MWBC feeds just the two 120V duplex GFCI's, nothing else.
What is best practice to do this?
I could run existing MWBC wires to a small panel, then install one double pole 15A 220V GFCI breaker and two single pole 15A 120V GFCI breakers, and new receptacles. Possible also to use the existing 120V GFCI receptacles and regular single pole breakers fed off this panel too, in this situation.
Or could leave the current two GFCI receptacles alone and take 12g wire pig-tailed from the ends of the MWBC to a 'spa' panel, change out the breaker in the 'spa' panel for a 15A or 20A 220V double pole GFCI breaker and then connect a 220V receptacle.
Or I could attach an inline 220V GFCI to the hot leads of the MWBC in a junction box.
Or I could use a 2000W step up/down transformer plugged into one of the 120V GFCI receptacles. It just seems redundant to convert the voltage when I already have it there, but a plug-in transformer may be the most code compliant and cheapest, way.
I can not run another wire from my main panel. I cannot replace the 20A double pole breaker in the main panel, with a GFCI breaker, as it is actually a quad breaker.
Any other ideas? Other than code won't allow any of it? Wife really wants the coffee maker so it is going to get done somehow.