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Community and Q&A

Humidity – Essick Console vs Aprilaire 500

Bruce Davis | Posted in General Questions on

Cold edge of Zone 4. New construction with above average insulation. About 5,000 sq ft/64,000 cu ft conditioned space on two levels, each with its own HVAC and one ERV interconnected to both HVAC. ERV runs 24×7.

In winter, mostly only use heat from downstairs and in summer, only use AC upstairs with portable dehumidifier downstairs. Blower door rated at 2.41 ACH50. HERS Index 21.

Both furnaces have Aprilaire 500M humidifiers connected to the hot water line of a tankless gas heater. They operate only when the furnace runs, which is not that often.

I have an Essick H12 console evaporative type humidifier with stat that puts out about 8 gallons per day and keeps the whole house at humidity levels up to about 45%. Only downside is some low fan noise in the family room/kitchen (well, maybe re-filling the 2.5 gallon tank 3 times per day). Humidity is evenly balanced throughout both floors of house (presumably through ERV and/or large stair opening between floors).

I have not used the Aprilaire yet, other than to check they work. Intuitively, it seems the Aprilaire, with usually only the downstairs furnace running less than continuously, the console is more effective and at least equally energy efficient.

The console says it uses 2.2A, I haven’t tested it. So, it’s running this 24/7 vs intermittently firing up the tankless gas repeatedly (wear & tear) and unknown quantities of un-evaporated water going down the drain. Both need once per year filter changes.

Admittedly, I don’t know how well the Aprilaire would humidify. That said, any thoughts about the Aprilaire vs the console for comfort, tankless gas wear & tear and energy efficiency?

Second question. I set the humidifiers per commonly found temperature & humidity charts:

+40 = 45%
+30 = 40%
+20 = 35%
+10 = 30%
+  0 = 25%
-10 = 20%
-20 = 15%

My understanding is this chart is to prevent condensation on windows, etc. Nonetheless, even at +10 and humidity set at 40-45%, I get no condensation. Humidifier is only a few feet away from a whole wall of double-pane glass (Pella Impervia Fiberglass). No sign of condensation at all.

Can I keep humidity at higher levels than chart recommends if there is no condensation? Thanks.

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  1. Expert Member
    Akos | | #1

    Efficiency wise, doesn't matter much. Both systems rely on heat from your furnace to evaporate the water. The bit of extra power for running the fans (inside the console, or on the furnace) is small compared to the energy required to vaporize the water. The issue is the connection to your tankless. If it causes your tankless to cycle, it is very rough on the unit. If it just runs at low fire, than you are fine.

    Besides condensation on windows, there could be risk of condensation inside your walls and roof. This all depends on how your house is constructed, some assemblies (walls with thick exterior rigid for example) are very tolerant of higher indoor humidity.

    Most of the water your are putting into the humidifier is going into your house structure somewhere. With a larger house, if the leaks are spread out evenly than it probably is not an issue. If the air leaks are in one specific area like a ceiling shotgunned with pot lights, than it can cause problems with mold.

  2. Charlie Sullivan | | #2

    Do you know if the house had a blower door test? Good air tightness can reduce the chances of moisture getting deposited in the structure, and reduce the rate at which you lose humidity and heat and reduce both heating and humidification costs.

    I don't think there's much reason to humidify above 40% at any temperature. I think you get the full comfort and health benefits at 40%, and if you enter the summer with the structure a little drier, you have a little more of a buffer before you need to start active dehumidification.

    1. Expert Member
      DCContrarian | | #5

      This. I don't equate "new construction with above average insulation" with needing a humidifier, I equate it with needing ventilation to remove the humidity created by occupant activities.

  3. Bruce Davis | | #3

    My tankless gas is a Navien NPE-180A. Not sure what you mean by running in low fire. I thought it's either on or off and if on it can have a low or high fire. Therefore, there would be no way to avoid dozens of on/off cycles a day just for the Aprilaire humidifier. If both furnaces run, guess that would be many dozen extra cycles per day on the tankless.

    To clarify, I should stick to the humidity chart even if there's no visible condensation. No rigid foam wallboard. Standard ZIP OSB covered by concrete stucco, Hardie board or stone. My air leaks are minimal, if 2.41 ACH50 on a large house is good. No pot lights or other bad items. Thanks for the reply.

    1. Expert Member
      Akos | | #6

      It looks like the minimum flow rate on the NPE-180A is surprisingly low at 0.04 l/min. I think this is because of the built in buffer tank and recirc. If this is the case and your humidifier uses more water than that, than it should be fine to run it off the tankless.

      I would turn on the humidifier, run your furnace by cranking up the heat and listen to your heater. If the heater is constantly turning on/off (you should be able to hear the flame light) with the humidifier running, than I would re-plumb to cold water. If it is just firing every couple of minutes than it should be fine. It does run the unit more but it would be no different than running hot water recirc.

  4. Expert Member
    Zephyr7 | | #4

    Rigid foam isn't a problem for humidity levels and in many ways helps you. The issue with high humidity and walls is that the moisture tends to migrate through the insulation in the wall and condense out on the inside surface of the exterior sheathing. This can result in mold growth in your walls. You can have a similar problem on the inside of the sheathing of the roof if you have a vented attic.

    I would stick with your chart but never exceed 40% humidity levels regardless of outdoor air temperature.

    BTW, "low fire" implies a multistage burner. If you find you're cycling your tankless with the humidifier, I would either run the humidifer on cold water instead of hot (which results in slightly lower efficiency in terms of water use to humidity level increase), or get a small 1 gallon "point of use" hot water heater and install that to run your humidifier. In most cases just running on cold water is an easier option, unless you're in an area with very high water prices.

    Remember to change the pad in your humdifier periodically too. They degrade over time, especially if you have hard water. As they degrade, you loose operational efficiency and use more water to raise the humidity level a given amount. Many people don't know there is a consumable part inside these humidifiers, so they never bother to check and do the replacement.


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