Find where the wire from the garage goes first and cap it off. This will leave the garage on the circuit as the only thing. Then run your new homerun to the bath, put in a GFCI with the new wire on the line terminals and the other wires to the load (making sure the line to the garage is not included). For the refrigerator, leave the GFCI but install a single receptacle (one connection as to two on a duplex outlet) wherever you can fish wire to the GFCI. Connect the feed to the single receptacle to the line terminals of the GFCI.

Thanks Spencer, you just gave me an idea... since the 1/2 BA butts up against the back wall of the garage I can just reroute the existing GFCI protected line that currently runs to the BA and connect it to a new single receptacle on the back wall of the garage... then switch that line to the LINE output side of the GFCI. This is easy to do because the drywall has been removed from the wall with the GFCI due to recent Earthquake strengthening.

Since I need to keep power to the upstairs baths during this reno I can temporarily connect the new home run line to the existing garage GFCI since its only a couple of feet from the panel. It will get routed to the panel when the rest of the new circuits are added.

I would have just ran a new wire to the where ever the garage is separated from the bathrooms, increase the size of the box if necessary, connect the new wire to the wire going to the bathrooms and then change the fist bathroom receptacle to a GFCI and put the second bath on the load side.

Or you could a put GFCI receptacle in each bath and not use the LOAD connections on any of them. That way a tripped GFCI will be in the room.

If the hair dryer is tripping GFCI regularly then it has a problem and should be replaced.

The current GFCI does not trip that often, but when it does it's inconvenient to run down to the garage to reset it. So, 'joed' is spot-on. His suggestion to put a GFCI in each bath is exactly what I am planning to do.

I'm just going to bite the bullet and run a new home run for the 1/2 bath (daisy-chained to baths 2 and 3) AND for the spare refrigerator in the garage. This way the garage, baths and spare frig will all be on their own circuits.

If you run a 12/3 wg to the 1/2 bath you can supply its receptacle with one 20amp circuit and can connect the wire that feeds the other two baths to the other 20amp circuit that will be available in the 12/3. Disconnecting the feed from the garage will leave you with a 20amp circuit in the garage, a 20amp circuit in the 1/2 bath, and a 20amp circuit for both of the upstairs baths. Providing a GFCI receptacle in the 1/2 bath and the first bath that is powered upstairs and feeding the second upstairs bath from the load side of that GFCI will protect the circuits and eliminate the need to run downstairs to reset a GFCI.

groundrod has an excellent suggestion. Since all wiring for the house comes from the garage attic and enters above the 1/2 bath, I'll run two new 12/3 circuits: one to the 1/2 bath which will feed its GFCI and also its 1500W 2 gal water heater that's going to hang on the bath/laundry room wall next to the furnace. It's receptacle is in the same wall just below the one in the bath.

Then I'll run another 12/3 that will supply power to a receptacle in the garage for the frig, and also connect to the line feeding the two upstairs baths.

Fortunately, I have room for 12 additional circuits in the panel as I'll be using 8-10 of those with all the planned changes.

If you run a new home run you can not put the garage on the same circuit. You must meet current codes and only service bathrooms with the new circuit.

joed, are you saying it would not be permissible to run 12/3 and have one hot wire supply power to the upstairs baths, and the other hot wire power to a refrigerator in the garage? If so, then I would assume I could also not use 12/3 to supply power to the 1/2 bath and it's small electric water heater via two wires of the 12/3.

It's not a huge difference to run separate 12/2 since all areas are already open, it just costs more and takes up more space.

I downloaded a trial version of MS Visio and I'm going to draw up all the circuits for the remodeling and post that drawing here for review. I would certainly appreciate some feedback :-)

Tom
You will be fine, as article 210 allows a multiwire circuit to be considered as multiple circuits.