We have AprilAir 700 piped to hot water it works absolutely fine. Make sure either use advance tstat, or move AprilAir control to the main area, most I have seen installed in a basement with sensor right next to it - pointless. Start from setting like 30%. https://www.aprilaire.com/whole-house-products/humidifier/model-700

865 steams are good, but do you really need this? And the maintenance ... steam rods must be replaced every year. IMHO AprilAir 700 are very easy to install and fool proof.

Have you talked to the HVAC contractor that performed the work on your home? If they can't help, they may be able to direct you to an engineer that may have worked on your home.

I will take a good look at the aprilair 700. Thank you for the recommendation. The hvac contractor wants to do steam consoles on all the air handlers. Just seems too ripe for mold if anything goes a little wrong. I know very little about it, but know that extra moisture sitting in ductwork is quite unsettling.

I'm not sure what your electric rates are, but steam can be a very expensive way to humidify air. If your ductwork or air-handlers are in unconditioned space (vented attic), I would not add humidifiers to them as you will be ripe for condensation in the ducts. The aprilaire 350 is a unique solution - it is a permanently installed stand-alone humidifier that has a built-in fan and gets its own short duct.