Ran into a different situation this week thought I might share what I found. Split system dual fuel HP, the aux heat was a upflow NG high efficiency 90% furnace located in the attic. (Now think about what that statement means) so far nothing particularly unusual about this set up I have seen it many times in my area.
The unusual part is the safety pan on this system had a moisture sensor in the pan that did not shut any unit off the outside condensing unit in the cooling mode or the furnace in the emergency heat mode. Keep in mind both of these units (the heat pump in the cool mode) and the (high efficiency furnace in the emergency heat mode) produces condensate. My thought when I observed what was installed in the attic how did the contractor wire the one single moisture sensor to shut down both units if there was moisture in the safety pan??? Did he just shut down the cooling mode and not worry about the furnace or did he just stick a sensor in the pan and not connect it to anything.
I wanted very much to revert to my old profession and trouble shoot this unit but I did not I just reported the moisture in the safety pan and the switch as non operational, but I still am wondering how it was wired and how I would have wired it had I been the installer ???