Helpful? 0

Prefered Location for a flow through Humidifier

Hello and thank you for any help you may be able to provide.
I have been given a quote for an installation of a Flow Through Humidifier.
I did read the installation guide and it says that the unit can be installed on either the cold air or warm plenum. I have a hot water tank that is blocking the access to the cold air return plenum and the installer wants to install the humidifier unit on the hot air plenum.
I also want to install central air conditioning in the spring. So my main concerns about installing the unit on the warm air side is,
#1- is it better to have the warm air side pushing hot air into the 7 inch bypass pipe that then blows warmed air through the humidifier evaporator pads and into the cold air side.( I would think that warmer air will be better than cool air to help evaporate the water on the pad).
If the unit is installed on the warm air plenum then that means, it will have cool air coming from the cold air return and pushing through the 7 inch bypass tube and blowing across the evaporator pads. As well, the furnace that this is being installed on is a 2 stage furnace so when the higher heating demands are not necessary, the furnace will push even cooler air thus making it even more difficult to evaporate the water on the pad.
#2- is if the unit is installed on the warm air plenum below the Air Conditioners A Coil then that means, the humid air leaving the pads will be passing close to and through the A-Coil. Will this excessive humidity effect the life expectancy of the A-Coil, and will the A-Coil trap moister on the coil that may then drain away.
If I had my choice, I would like to see the humidifier installed on the cold air plenum. Do you think I am justified in asking to have it installed on the cold side.
My main question here is, would it truly better to have the humidifier installed on the cold air plenum with the 7 inch bypass pipe coming off the hot air plenum and pushing air across the humidifier pads, or am I just over concerned.
This is my retirement home so I would really like to do things right to avoid any future problems etc...
Thanks for your help on this inquiry.

Dave Sheard. Ottawa Canada.

Asked by David Sheard
Posted Sat, 01/25/2014 - 08:21


5 Answers

Select your preferred way to display the comments and click "Save settings" to activate your changes.
Helpful? 0

Best case would be that your home is air tight enough to not install the humidifier. Air tight homes have high enough humidity that they need moisture actually lowered via an air exchange system.

Also you should talk to your local contractors and have them install any system only in the way they have knowledge and are comfortable guaranteeing.

Answered by aj builder, Upstate NY Zone 6a
Posted Sat, 01/25/2014 - 13:23

Helpful? 0

Thanks for the reply but... We just moved into this new home. I watched as the home was being built and we have excellent vapor barrier installed with excellent levels of insulation in walls and attic space. I too was surprised after moving in only 8 days ago, to see levels of only 21% Humidity in the house. We are getting static shocks and you can just feel the dry air. My HRV is completely shut off and we have a large pot of water boiling away on the floor of the kitchen. The humidity level is getting up to 31 % and I have the furnace fan running non stop to help circulate. I can not figure out why the home is so dry considering it is a new home construction. I had a humidifier installed at my last house that was only a 6 year old home and I was able to maintain a nice 38% during the winter and I also had my HRV run continually to provide fresh air exchange 24/7. There are so many conflicking opinions regarding HRV's, Humidifiers, etc... I was hoping I could get a unbiased expert opinion. Thanks for any other advice from the experts at Green Building

Answered by David Sheard
Posted Sat, 01/25/2014 - 13:47

Helpful? 0

Sorry, but I'm going to repeat what AJ said. The first thing to do is have blower door and duct blaster tests done. You have too much air leakage to maintain the humidity that's already there. Without testing, you have no way of knowing how much the HRV should run, whether or not the heating system is causing air loss either through duct leakage or supply/return imbalance, and so on. If your heating system has a fresh air intake, it is possible that running the furnace fan continually is just moving more dry outdoor air into the house. In tight new construction it is more likely to have excess humidity than lack thereof, and you should really measure the air and duct leakage and identify other possible issues before installing a humidifier.

Edit to add: the same person who does the above should also measure HRV airflow.

Answered by David Meiland
Posted Sat, 01/25/2014 - 14:20
Edited Sat, 01/25/2014 - 14:49.

Helpful? 0

Well Thanks for the info. It seems that nothing is ever easy,lol. I would like to say what my theory is in regards to new home air quality control, and if any one else wants to put their opinion in, I would love to hear what others have to say as well. Here goes, New homes with tight wrapped vapor barriers that keep air trapped inside need an exchange of air to keep the air fresh. Unless you keep windows open slightly, you would need a HRV that would exchange about 2 thirds of total air every hour. So now that you are pulling in fresh air you may then have to consider humidifying it. Simplified HRV's that are connected to a typical forced air furnace system usually need the help of the furnace blower to help circulate the air from the HRV. The small blower fans in a typical HRV are not strong enough to circulate the entire home. With all this said, we would now have a home that is tightly sealed, well insulated, has windows that can be kept closed, pulling in fresh air that gets humidified and circulated to the entire house. Yes this costs money, but the air quality is maximized. Thanks to all that may wish to comment. Dave Sheard, Ottawa.

Answered by David Sheard
Posted Sat, 01/25/2014 - 15:27

Helpful? 0

Not sure what you're basing your HRV fan critique on. They are in fact powerful enough to give you the air exchange you need. Running the furnace blower to exchange air is going to consume a lot more electricity, because the blower is bigger. Hopefully your HRV has its own ductwork. You are better off with a well air-sealed house than a leaky one. Yes, you will need to use some electricity to provide fresh air, but you will use less energy to heat, and you will be a lot more comfortable. Your desired ventilation rate is more like one change every three hours, not two. If you do the air sealing and duct sealing, and commission the HRV, you can dial all of this in nicely. Not uncommon to have some issues to work out in a new home.

Answered by David Meiland
Posted Sat, 01/25/2014 - 16:09

Other Questions in Mechanicals

In Energy efficiency and durability | Asked by Anthony Hughes | Aug 8, 14
In Green building techniques | Asked by Stephen Youngquist | Aug 21, 14
In General questions | Asked by Lucyna de Barbaro | Aug 22, 14
In General questions | Asked by Dan McGonigle | Aug 22, 14
In General questions | Asked by Steve Young | Aug 16, 14
Register for a free account and join the conversation

Get a free account and join the conversation!
Become a GBA PRO!