Does the weep water come out of the gun onto the floor then down the drain? Or once the gun is in the wand holder, is the other end of the wand holder plumbed into the drain?
If the weep water runs on the floor at any point, from the gun or the foam brush, the floor heat has to be kept on to keep the water runoff from freezing.
Again, even IF there is no water weeping in the bay at all (using whatever system you chose), once a customer starts to use the bay, the floor heat has to be on and set at a temp. that will allow the customer to walk on the "wet" floor from the wash and rinse process and not slip or fall due to ice buildup.
I lower my floor heat return temp to 50 F in the beginning of the winter season. As the temps fall, I have no choice but to raise it to 55 then 60 then 65 etc. depending on the weather conditions and IF I think I will get wash customers.
There are too many variables to the floor heat debate. Do you have
doors on your bays? Does the wind whip through them on a normal winter day? Does the sun every reach the inside of the bay on rising or setting?
All of these things will have an effect on the floor heat settings.
Years ago I would just "Set it and forget it" all season long. NOT anymore, it's too costly!