Low voltage AC inside power and ground plane

[braincat]

Newbie here... I am working on a thermostat pcb; the board receives 24V AC from the furnace, and uses LM2596 to convert it to 3.3V DC.   Logic runs on ESP32 which switches three through hole relays (fan, power, heat/cool).  The board has a ground plane and a 3.3V plane covering the whole board.  I have a (hopefully) very simple question: is it ok to run 24V AC traces inside these planes, or would I be better off not doing that?   I didn't give it a second thought at the beginning, but recently discovered a bridge of solder between one of relay contacts that switches 24VAC, and a 3.3V plane.  I would lean towards routing AC traces away from the planes if I were doing the board from scratch, but unfortunately it is almost complete.

Thanks.

[S. Petrukhin]

The use of copper polygons does not have any clear rules and it is often a creative process based on calculations and experience. You have gained experience with the jumper and now probably want to make the interval longer to protect against jumpers. But this is a question of making a board and it has little to do with the polygon itself - in good conditions, jumpers do not arise. Copper polygons require attention in high-frequency and power circuits, in other cases it is most often saving solution for etching boards. Perhaps your device could do with just one layer.However, the separation of circuits of different voltages in space is a good practice. It is better to group 3.3V circuits in one area and 24V circuits in another so that they have as little overlap as possible.