I'd like to use the electronic humidistat in my TST412MDMS rather than the mechanical humidistat installed with my TrueSteam system. Unfortunately the documentation for the TrueSteam only shows Honeywell electronic humidistats (which have two HUM connections just like the mechanical humidistat). The TST412MDMS has only one connection (not two); the "HM" or "humidification relay" signal. Any recommendations for the best relay to use (book says 90-290Q or equivalent)? Is there another way to wire this without a relay? If a 24V relay is the way to go, do I need a separate 24V transformer or can I pull the 24V from the TrueSteam (neither 24V connections are used at the moment)?

BTW, my TrueSteam is configured to call for Fan on it's own (even when there is no call for heat). Absolutely love my TrueSteam; nose bleeds have stopped and I'm man enough to admit my lips have never been so supple!

Liked my TST411MDMS until I was nailing something on an adjacent wall, heard a crash and found my thermostat lying on the floor with a shattered screen (sill worked BTW, so it kept the family warm until the new TST412MDMS arrived). Liking even more the added features of the TST412MDMS.