Honeywell TrueSTEAM Humidifier - insufficient output for home


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Old 01-07-09, 06:04 PM
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Honeywell TrueSTEAM Humidifier - insufficient output for home

First, I really like the Honeywell TrueSTEAM design (and VisionPRO IAQ Control) but am disappointed by its low output.

Some stats on the house: 1-yr old, 3-story plus unfinished insulated basement, ~5K sq ft total, one furnace for the basement and 1st floor, and a second furnace for the 2nd and 3rd floors. The entire 1st floor has wood flooring and the 2nd floor is half wood and half carpet. The house was not built like those in the Midwest, but it is reasonably tight for the age. The plan was to install a 9-gal/day unit on each furnace plenum, which meets Honeywell's recommendation.

I installed the first 9-gal/day unit on the lower furnace and ran it for nearly two weeks. At that point it had a tough time keeping the humidity at 35% given only a 40F temp difference (70F inside vs. 30F outside). And this required running the furnace fan nearly 20 hrs/day AND closing the 6-inch fresh air intake to the furnace return side. If the temp difference drops to 25-30F, i.e. the outside rises to 40-45F, it has a tough time getting the humidity to 40%. What's the point of the VisionPRO IAQ if the humidity cannot reach the desired set point?

The upper unit has not been installed yet. For now, I have one portable 4-gal/day steam humidifier on 2nd floor and a second on 3rd floor, which helps to keep the humidity on those levels in the low-/mid-30% given a 40F temp difference.

There is also an issue w/ the upper furnace that has both its insulated supply and return ducts in unconditioned attic space. If the TrueSTEAM requires the furnace fan to run for long periods w/o heat, there is a risk that the moisture will condense on the inside of the cool ducts thereby increasing the risk of mold.

How can I resolve this low humidity problem? Is the solution to use a high-output (e.g. ~20-gal/day) 220V steam generator that fits on the plenum?

I think it is a waste of energy to run the furnace fan nearly non-stop and still not hit the recommended humidity set point. I think the humidifier should be able to hit the set point during the heating cycles or perhaps w/ a little extended run of the furnace fan.

Any suggestions would be greatly appreciated.
Thanks,
Michael
 
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Old 01-07-09, 08:31 PM
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Hi Michael, all houses haves an air exchange rate where we can measure and calculate how often all of the air inside your home is escaping and being replaced by cold dry air from outside. Since you are struggling to raise your humidity, I suspect that there is too much air leakage. Chimney chase, electrical and plumbing penetrations, and a long list of hidden construction details all lead up to too much air loss. By comparison, I have worked on new homes where the builders went to extremes to seal everything and got the homes too tight. Those home owners are facing running de-humidifiers all winter, too much moisture.

Most of the air sealing can be a DIY project, and or you can bring in an energy auditor to run a blower door test to search out where those air leaks are, especially the ones hidden between floors, above kitchen cabinets, under bathtubs, and a variety of places you might never expect. Between the pressure meter and the infrared camera, you will be amazed.

Once you have your air leakage reduced to the correct level, then your humidity issues will be greatly reduced as well as your heating costs. You may find the second humidifier is not even needed.

The other benefit to reducing air leakage, is all of that humid air is leaking into your walls and ceiling where it can and does condense out as moisture risking hidden mold or wood damage. Adding more moisture simply makes the problem worse.

DIY some air leakage or bring in an energy auditor and your problem will be gone.

Bud
 
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Old 01-08-09, 04:42 PM
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The house was not built like those in the Midwest, but it is reasonably tight for the age. The plan was to install a 9-gal/day unit on each furnace plenum, which meets Honeywell's recommendation.


Bud's idea's make sense and your first step should be to make sure your leakage is minimized.

As far as the TrueSteam humidifiers are concerned, there are two problems. First you are sized wrong. You selected the 9 gallon unit which covers a maximum of 2500 square feet so in a normal situation you would push that model to the limits and the fact that you have all hardwood makes it even more necessary to go with the 12 gallon unit. If you had all carpet you could probably get away with the 9 gallon.

Another problem I see is that a portion of the humidity dispensed to the 1st floor of your house is going to rise to the 2nd and 3rd floors and this is probably what is creating the problem. Install the other unit as you originally planned or trade the 9 gallon you haven't installed yet in for a 12 gallon then swap out the 9 you have installed with the 12.
 
 

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