I have a dual fuel system with upflow configuration so the coil is on top of the furnace. The heat pump isn't operational now, but the furnace is running and there is heat coming out of the condensate drain. In cooling mode the water in the p-trap will prevent this, but in heating mode there is no water in the trap. It's lost heat. Is there any way to stop this? Maybe a different condensate drain or p-trap configuration?