My wife and I have a new (less than 2 years old) house in Northeast
Ohio, and we've determined that we need a humidifier. We're seeing the
typical symptoms of dry air that are reported in the houses and in
people.

Consumer reports did not put much effort at all into testing the
furnace mounted models, only saying that "All should perform
adequately.". Looking around on the web & talking to people at work, I
find that Aprilaire is a decent brand, so I've ordered one.

Prior to ordering it, I've read the installation manuals I could find,
located & marked the place on the duct where I'll install it & run the
supply & drain lines.

There are a couple of questions that I have not found answers to as I
STFW. I would appreciate any words of experience that the group can
offer:

1. The installation diagrams I've looked at sometimes show the
humidifier unit on the supply duct and sometimes on the return duct.
Either way, warm air will flow from supply through the element to
return. Therefore, it seems to me that the humidifier element should
not care which direction the air flows through it, and it doesn't
matter on which side (supply or return) the unit is mounted. Is this
correct?

2. I specifically bought the Aprilaire 600 (instead of the Hamilton
12HF from Lowe's) because the Aprilaire's controller has an outside air
temperature sensor. (Price was a wash, anyhow). I understand that the
only purpose of this sensor is to decrease humidity when it's colder
outside (and therefore colder on your windows & outside walls) to
prevent condensation from occurring. Is this correct? Would anybody
who is currently running one of these in automatic mode, maintaining
humidity without adjusting the dial or seeing condensation please
report their success? Or if not, then report failure?

Thanks for your assistance!