Humidifier is installed in central HVAC system main return and is functional (the supply plenum was not large enough to install it downstream of the heat exchanger). It is controlled by the HVAC blower control circuit power and a newly-installed humidistat. Plumbing work for hot water system still needs to be completed (temporary through slop sink hose connection). Also need to install receptacle for 120 VAC for fan, and cut in permanent drain line (temp in sink!). Humidity reported by thermostat as 23% before install; noticeably dry in house and train room.