So would I replace a 3-wire dryer feed in my house with a new 4-wire dryer feed? Yes, mainly because of my perfectionist tendencies.
Do I recommend that others do so? I'm not sure it is worth it, as long as the dryer on the 3-wire feed has the chassis properly bonded to the neutral. I.e. I bet there are other improvements that could be found that would provide more safety bang for the buck.
Would a GFCI for a 3-wire dryer or oven feed improve safety? Sure. I'm curious as to whether there would be an issue with nuisance trips. If the chassis of the dryer or oven, which is bonded to the neutral, gets electrically connected to something bonded to the EGC, then that neutral/EGC connection could well trip the GFCI. I don't think a person would provide a low enough resistance connection for that to happen. But, for example, if your refrigerator and your 3-wire fed oven are both in contact with a metal backsplash, it could happen.
LTLFTcomposite said:
Part of the rationalization in running the 10/3+G for the dryer is I could repurpose the 10/3 w/o G for a hardwired evse, but considering the house only has 100A service along with the panel congestion that might not be too practical (I figured I might be able to find a 50-30 tandem breaker and put the evse on with the range, I think that's the only expansion option remaining)
Sound like a fine plan. You will be committing a small violation by reidentifying the neutral in the 10/3 w/o ground as an EGC (that is only allowed "Where the conditions of maintenance and supervision ensure that only qualified persons service the installation" [250.119(B)], which generally means industrial installations.) I would check the NEC load calculation for the 100 amp panel, but that is quite conservative. If the current load calculation is under 100 amps, the actual current on the service conductors is very likely under 75 amps at all times. In which case, even if the extra 30 amp EVSE pushes the load calculation over 100 amps, it wouldn't push the actual current on the service conductors over 100 amps.
As far as your panel being full, you could add a subpanel by moving a couple circuits over to the subpanel. That would free up space in the main panel for a breaker for a feeder to the subpanel.
Cheers, Wayne