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Honeywell TrueSteam Humidifiers are (finally) here!

This article was written to describe features and benefits of the Honeywell TrueSteam family of whole-house humidifiers and explain the difference between the models and control options.  This article will also serve as a selection guide (there are 8 models to choose from).

Honeywell made a huge splash in 2007 in the residential HVAC marketplace with the introduction of the TrueSteam humidifier.  These units weren't actually available until 2008, after majority of the humidification system had passed. 

These units are much different from the "flow-through" units found in many homes today.  They are also much more advanced than the steam humidifiers of the past.  Essentially, these steam units are designed in response to trends in the HVAC industry.  Heating and cooling equipment is much different today than it was just a few years ago, with the trend towards high-efficiency, variable speed, dual-fuel, and heat pump systems.  Because of how these systems operate, yesterdays "flow through" humidifiers often fail to deliver the humidification that homeowners desire. 

TrueSteam takes the best features from current steam humidifiers with their efficiency, performance, and decreased water consumption, and combines it with ease of installation, reliability and value of flow-through humidifiers.  TrueSteam is different from others because it operates independent of equipment operation.  And, with its near 1:1 humidification delivery rate, TrueSteam delivers enough humidification to keep you satisfied.

The main benefits of a TrueSteam humidifier:

Low Water Consumption
Very flexible installation options
Easy to install
Works independtly of heating equipment (does not rely on heated air from furnace to work)
Variety of control options
Easy to maintain
5-Year Warranty

What model TrueSteam humidifier do I select and what is the difference between the 3 control options?

Honeywell manufactures the TrueSteam with 3 different capacities - 6, 9, and 12 gallons per day.  Within these three capacities are 3 different control options.

The first thing to consider when selecting a model is the size of your home.  Here are some very general guidelines for sizing these humidifiers:

6 gallon models will humidify homes up to around 2,000 square feet
9 gallon models will humidify homes up to around 2,500 square feet
12 gallon models will humidity home up to around 3,000 square feet

NOTE: If your home is well-insulated ("tight"), you will get more mileage out of your humidifier and a smaller capacity unit may work well for a larger space.


Even though there are only 3 base humidifier sizes - there are actually eight different models in the TrueSteam family.  This is because each humidifier is bundled with a control (humidistat) and there are 3 different controls to choose from.

Control Option 1 - H8908 Manual Humidistat 
This is bundled with the following models:
HM506H8908 - 6 Gallons per day
HM509H8908 - 9 Gallons per day
The H8908 humidistat is your basic, bare bones control.  It's advantages are simplified control and low cost.  It closes the humification circuit manually whent he humidity drops in the home.  This humidistat will not  provide any automatic control based on outdoor temperature.  It can be mounted on the wall or on the return air ductwork.

Control Option 2 - DG115EZIAQ TrueIAQ Digital Humidistat
This is bundled with the following models:
HM506DG115 - 6 Gallons per day
HM509DG115 - 9 Gallons per day
HM512DG115 - 12 Gallons per day
The TrueIAQ digital control provides a digital display, and automatic control based on outdoor temperatures.  This control ships with a (wired) outdoor temperature sensor.  The TrueIAQ can also be used to control your home's dehumidification and ventilation systems.  In our opinion, if you are spending your money on this advanced humidifier - you should probably be considering this advanced control.

Control Option 3 -  YTH9421C1002 VisionProIAQ Total Comfort System
This is bundled with the following models:
HM506VPIAQ - 6 Gallons per day
HM509VPIAQ - 9 Gallons per day
HM512VPIAQ - 12 Gallons per day
The VisionProIAQ control would be the appropriate control option if you plan to change out your whole house thermostat.  The VisionPro IAQ would install in place of your current thermostat and become the central control of all temperature, humidification, dehumidification, and ventilation products in your home.  The VisionPro IAQ has about any bell or whistle you can imagine.  It is comprised of a thermostat (looks just like a standard Honeywell VisionPro) and an Equipment Interface Module (EIM).  The thermostat only requires 3 wires and is a very convenient retrofit for and older thermostat.  It talks to the EIM, which is typically installed in the mechanical room with heating, cooling, humidification equipment.  Again, this control option replaces your existing thermostat.


The TrueSteam system offers extreme flexibility with regard to installation. Each TrueSteam unit can be installed remotely from the heating and cooling equipment using remote mount kit.  There are two options:

10-Foot Remote Mount Kit
20-Foot Remote Mount Kit

With a remote mount - all that is required on the furnace plenum is one, 1-3/4" diameter hole.


Because the TrueSteam humidifier using a heating element to turn water into steam - it does draw a fair amount of electricity.  The 9 and 12 gallon models may require a dedicated electrical circuit:

Power draw by model:
6-Gallon HM506 units -  7 Amps
9-Gallon HM509 units - 10 Amps
12-Gallon HM512 units -  12 Amps