Installing a Bypass Humidifier - Honeywell TrueEase

This is a short post describing my installation of a bypass installation. There are a few basic types central forced air furnace humidifiers - one uses a fan to push air through a humid pad, and one uses differential air pressure between the return and distribution ductwork to push air through a humid pad. Since the electrical efficiency of very small electric motors is not very high, and the electrical efficiency of the furnace blower which creates that differential pressure used in a bypass humidifier is likely much higher - especially since in my case I upgraded to an electronically commutated blower motor - I decided to go with the bypass humidifier for greater system efficiency.
Honeywell TrueEase Bypass Humidifier
I've been engaged in an indoor air quality project - I have a number of issues that I've been tackling since renovating this house and I'll post about the various solutions as I work through them. In short - very dry air in the winter, very humid air in the summer, and optmizing the HVAC performance, especially since one of the household members has Asthma.

So - the whole house humidifier is obviously aimed at the very dry air in the winter. I've been tracking humidity levels for the past two heating seasons, and I've been getting down to 24 or 25% relative humidity, and all the problems that go with humidity this low. Cracks opening up in hardwood floor, nosebleeds and dry throats, dry coughs, and the like. It was finally time to sort this out.

I've posted about wall acne, and my aversion to having a wall full of different devices. I started this project with my thermostat and venmar ERV air exchanger controller - and I've traced my problem with high humidity levels in the summertime with the lack of integration between the furnace blower control / air conditioning compressor with respect to the air exchanger demanding (furnace interlock) with the blower. When the air conditioning compressor kicks off, the Venmar air exchanger forces the blower motor to keep running - which effectively re-evaporates all the condensation sitting on the evaporator coil in the fan coil unit. Result - the humidity removed from the air by the air conditioning system just gets put back into the airstream and redistributed by the furnace blower. So - I need to change my Venmar control scheme to force a shutdown of the blower immediately following air conditioning cycles with the heat pump - to allow condensed water on the evaporator to drain through the condensate drain.

I also require central control of the humidifier in the winter time. This lead me to look at the latest generation of smart thermostats - in an attempt to get better control over the HVAC in my home, and address my air quality issues. I found that the Nest thermostat doesn't have the capability to intelligently control ventilation, has a single output to control humidification, and has the ability to control the air conditioning to control de-humidification. Similar situation with the Ecobee 3 thermostat. Finally, I found the Honeywell Prestige 2.0 IAQ thermostat - with the equipment interface module, it has three user outputs that can control ventilation (ERV/HRV), humidificationa and dehumidification. So - part of this plan included upgrading my thermostat and ERV control to the Honeywell Prestige IAQ thermostat.

Why the discussion about the thermostat? Because the Prestige 2.0 has integrated humidity sensing, both indoors and outdoors with the wireless outdoor temperature module. So - it is equipped with the sensors and programability to control a whole house humidifier, without an additional humidistat or control system. The Prestige 2.0 equipment interface module can switch the control voltage with a single dry contact, and to keep the wiring simple, I decided to ensure the Bypass humidifier I selected worked with the same control voltage as the rest of my HVAC system - 24VAC.  The whole house humidifiers that are available at your big box hardware / home improvement stores are typically wired for 120VAC, and then wire to a humidistat for control. I wanted to avoid 120VAC altogether, and just use the Prestige 2.0 EIM dry contact to actuate the bypass humidifier.

I found that the basic Honeywell TrueEase Bypass Humidifier would be perfect for this application - requiring only 24VAC to actuate the solenoid to start water flow to the humidifier. I also added a 24VAC damper to open and close the bypass air duct to the humidifier, to increase system efficiency of the furnace blower when humidification is not required (shutting off the bypass airflow).

Honeywell TrueEase HE200 bypass humidifer
One thing I should mention is that this humidifier model is directed to HVAC contractors and not homeowners. It takes some control system knowledge to tackle this installation - it's not terribly complicated, but if you are not completely comfortable undertaking this kind of installation - call on a reputable HVAC contractor to do this work for you. Take the time to read the instructions - not only to get the installation done right, but to verify that the equipment you've selected is right for your application - online manuals are excellent to verify that the part you've selected will be adequate.
I added a branch off the closest cold water line, with a brass ball valve to shut off water to the humidifier. The TrueEase humidifier comes with a saddle valve that perforates a hole in your supply pipe - but I was afraid of that leaking so decided to cut my 3/4" supply line, and solder in a T and a branch for reliability. 

While there, I took my trusty P-Touch and labelled all the branches at this end of the cold water line - irrigation, outdoor tap, humidifier supply. These things tend to be obvious to certain people and a mystery to others - so I like to label things as I go to make things clear for potential future homeowners, and any tradespeople that need to work in the house. 

Installation of the humidifier itself is pretty straighforward, use the template to cut your access hole to the ductwork using the cutting template provided. A jigsaw made a nice clean cut fairly quickly.  

The humidifer hangs in the installation hole with two catches, then two screws keep it in place. The bypass duct inlet can be oriented left or right, and the humidifer pad can be independantly oriented left or right to customize the installation. These modifications can be made without tools. 
Bypass ductwork - air pressure from distribution duct forces air back through the humidifier pad into the return duct just ahead of the evaporator of the fan-coil unit. A spring closed damper only allows air to flow when the control voltage is present. 
Side takeoff to provide air to the Bypass Humidifier
To help save energy for when the humidifer isn't running, you can have the humidifer control clode a damper to close the bypass duct. This avoids short circuiting airflow between the supply and return ducts when not required for humidifying. You can purchase these dampers normally open, or normally closed. I purchased a normally closed damper, and wired it in parallel with the humidifer control, so that it only opens when there is a call for humidification from the thermostat.

24VAC normally closed 6" round damper

I decided to upgrade the nylon hose provided with the humidifier to copper tubing, just for a stonger, cleaning installation. I used a brake line tubing bender to get clean 90 degree bends in the line, then trimmed the final length at the unit once everything was lined up all the way from the supply tap.
Copper supply line connected to the plastic quick connect fitting on the humidifier
Supply and drain lines connected. For the drain, I used 3/4" CPVC pipe - same as my condensate drain line, and put in a P-Trap to avoid any odours coming up through the line. Consider installing a union fitting before the trap, to allow for easy removal and cleaning of the trap in case of blockages.
The control connections are the blue cables - 24VAC - 2 wires to control the solenoid controlling the water. 
Water supply and drain connections.


So - it took about a day to get this done - taking the time to upgrade the typical installation to soldered ball valve shutoff, copper tubing, 6" round ductwork with automated damper. The humidifier has been running frequently and quickly increased the 25% humidity level to over 30%. I'll talk about the control of the humidifier when I get into the operation of the Prestige 2.0 thermostat

5 Year Update

Still working flawlessly after 5 years, helps so much with managing household humidity in the winter, particularly important considering my son's asthma. 

Sources and Links

I hope you found this post useful. Feel free to ask questions in the comments section below. I answer all questions.


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