Install a flow through humidifier on either side of the duct

furnacehumidifierinstallation

I was about to install a Wait6000 whole home humidifier when I hit this snag in the plan.

On page 3 of their manual (PDF), it says the cold air return duct must be at least 10" wide. The diagram show the humidifier install on that skinny side of the duct.
My duct is only 8" wide. I was planning to install it along the other side where it is plenty wide enough.

My question is, does it matter if I install it on the length of the duct? It would meet all other criteria.

Best Answer

It does not matter if it's on the skinny or wide side, as long as the surface the unit mounts on is 10" wide. There may be issues if the duct were say, 3x10, but any duct large enough for the whole house will be fine with the unit installed on any surface at least 10" wide.