Along with a newly installed Trane high efficiency heat pump, I had a Trane whole house humidifier
installed. The humidifier has been tested by the installer to make sure it has positive air pressure flowing into it, and that the water is coming on a running through the approximately 12"x12" evaporator
screen whenever the heat comes on. The problem is that in a relatively small (1300 sq ft) condo, the humidity is almost completely unaffected by this unit. The difference between turning it completely off and turning it on at the max setting, is only a difference of 2 or 3 % humidity. With the unit set at 40%, the humidity in the house only goes up to about 25%. This has been verified with 2 different humidity monitors.
After several visits the Trane installer is saying there is nothing else they can do other than maybe switching it to run off of hot water rather than cold water to try and get it to evaporate the water faster. But would seem to be ridiculously inefficient and expensive to run water out of the home's hot water heater
each time the heat comes on. One other thing to note is that this is a downdraft configuration (the unit is installed upside down and is in a closet on the loft level of the condo). So the positive pressure is being tapped from the output of the bottom of the unit via an 8" flexible duct. This is being run back up to the top of the unit where the humidifier is installed. And the humidified air is presumably then being pushed back down through the heating coils of the unit and out through the output duct work.
Additional Note - The following model numbers are on the installation receipt, but I don't have the humidifier Model number. It does however have a "TRANE" logo on the outer plastic housing.