In article , "martin" wrote:
current setup

Bathroom distribution:

2 breakers : 1-15A GFI, 1-15A, 1 pole duplex .
2 wires from breakers, 1-2wire, 1-3wire

2 wire cable
- connected to A of 15A duplex breaker
- running to GFI receptacle

3 wire cable
- 1 hot connected to B of 15A duplex breaker
- runnig to lights, fan
- 1 hot connected to GFI breaker
- running to floor heating cables

- neutral connected to GFI breaker

is this setup OK?

Nope. Won't work. John Grabowski got it right in his post; toller (as usual)
got it wrong, and you're risking a fire if you follow his advice.

Does the GFI breaker neutal works ok if shared between 2
breakers?

Nope. Doesn't work at all.

Originally this setup was planned beacuse the receptacle is on the other
side of bathroom.
3 wire cable runs to wall with switches for lights, afan, and floor heating
thermostat. Will the circuit work, or is there a chance of GFI breaker
tripping?

Nope, won't work - GFCI is guaranteed to trip almost every time.

Now, you *could* get a 240V (two-pole) GFCI breaker, and use that for your
3-wire cable, but:
a) they're waaaay expensive; much cheaper to run new cable, and
b) you probably need to run new cable anyway, because you need 12ga copper for
the 20A circuit that is required by Code.

If needed, I can rerun the cables, but beforte I get into it, I want to be
sure that it is required.

Got the order of those two steps reversed, it seems to me. :-)

--
Regards,
Doug Miller (alphageek at milmac dot com)

Nobody ever left footprints in the sands of time by sitting on his butt.
And who wants to leave buttprints in the sands of time?