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  1. #1
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    Aprilaire 800 Steam Humidifier - Will it work, Denver area 2 story home?

    Hello

    Had a HVAC contractor (national name that's been in business decades) come to clean our ducts and while here suggested that this unit would solve our extremely dry interior climate that's causing dry skin, too much dust etc.
    Here in the Denver/Boulder CO area it's very dry in winter, especially with forced air heating throughout the entire home.

    We have a 5000sq ft home, basement, main living level (ground floor) and upstairs bedrooms.
    Home entrance area on main level is very open, with vaulted ceiling all the way up the stairs to the upper hallway that leads to all the bedrooms - I'd estimate the ceiling is probably close to 20ft high.

    Main Furnace in basement utility room for basement and main living area.
    Secondary furnace in attic for upper floor (4 bedrooms) only - ducting is very different from main furnace, in that it's all these insulated flexible hoses coming from a central plenum that are suspended throughout the attic, to the vents in the ceiling of each bedroom upstairs.
    In addition to these flexible supply hoses, there's 3 much larger diameter flex hoses that connect to large/square ceiling returns grilles - we change the filters in these so I know these are the returns.

    HVAC company suggested we install the Aprilaire 800 in the basement furnace, running it at it's maximum 240v output, upto 34 gallons of water turned into steam per day.

    Was about to pull the trigger on the install, but thought I would call Aprilaire directly to get their opinion.
    They said we would most likely be disappointed with the results, and the upstairs bedroom floor would likely not improve much at all.
    The tech explained that where there are vaulted ceilings, it's very hard to get the moisture up to the upper floors.
    They said that they would strongly suggest a second unit in the attic furnace, but there is no water supply to the attic furnace, so we would have to tear out walls to tap into bathroom water supply, and then also drain.
    The drainage may not be a big issue since there are several 2" black plumbing pipes venting up through the attic and out through the roof of the house - I'm guessing the humidifier could connect to one of these vents, since these will be connected to drains in bedroom bathrooms, and the humidifier is only going to be dripping water, so would not impede vents. Right?
    What about the type of ducting in the attic furnace? I'm concerned there may be the potential for mould in these flexible duct hoses?

    Aprilaire also suggested a different kind of unit (the 350/360 models) which are essentially 'plug in' units that mount in the ceiling joists in the attic and push humidity from the upper floor ceilings>
    The issue is that this house is 15 years old and the attic is not 'conditioned' so gets extremely hot in summer and stays pretty hot in winter - this would likely negate such a humidifier? Right?

    Aprilaire also suggested that if it was possible to run a line from the 800 in the basement to the attic furnace, then this could work, but that seems like a big job, since the only way to feasibly do that is to follow the main exhaust from the hot water heater next to the furnace as that vents up through the middle of the house into the attic and finally venting through the roof to the outdoors. Not sure if this would be to code to have a humidifier line running next to this vent?
    This could also be a good way to run water supply (1/4" copper) to a humidifier unit in the attic, but again I am not sure what code has to say about this?

    I called the HVAC company with this info and they said Aprilaire is wrong and the single 800 series at 240V would provide humidity to the entire home and we would be very happy.

    Sadly, I'm inclined to believe Aprilaire since they don't have a vested interest as I would not be buying the unit from them directly, whereas the HVAC company would be making several thousand dollars to install a unit that costs a fraction of the total cost.

    Appreciate advice, it would be a shame if the HVAC guys were BS'ing me just to make a buck - surely they know just how dry the climate is here and whether the unit would work or not?
    It would be several thousand to install, so I don't want to get screwed over to find that we are still suffering from dry conditions upstairs.

    Thanks.

  2. #2
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    Thread Starter
    bump??

  3. #3
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    50/50 chance the bedrooms will gt enough moisture during the day while the bedroom doors are open. Once the doors are closed at night/bedtime. If the second floor system doesn't have a return outside of the bedrooms, the bedroom RH will drop.
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  4. #4
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    You really don't have a lot of options. The humidifier installed on the downstairs unit might be the best you can do. With the real possibility of water lines freezing in the winter and causing LOTS of damage, I would completely forget the idea of one going in the attic.
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  5. #5
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    I put an 800 in an old 2 story home built in the 30's and set the 800 to max. The house has 2 systems one in the basement the other in the attic. The 800 is on the basement system. The owners tell me it does great on the main floor but doesn't do a lot for the 2nd floor. How about that a manufacturer knows what they are talking about! The idea of running a line to the 2nd floor may work if you can insulate it well enough otherwise the steam will all condense and do no good. Adding one to the attic unit is not a good idea. Besides the possibility of freezing the plumbing code frowns on wet vents, running water into the vent part of the drainage system. On all new construction they run what they call a revent where a pipe is run around where the water enters the drain to keep the vent dry.

  6. #6
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    My experience has been that a humidifier on the first floor is adequate for both floors provided the floors are open to each other. Several years ago we had a customer with the same situation you have. We suggested installing a humidifier on the system for the first floor and make a provision so water could be provided to the attic if it became necessary to add a humidifier to that system. In this case it was a flow-through humidifier which has less capacity than the steam humidifier.
    After several years they've never needed one for the attic system.
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  7. #7
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    Thanks for the replies guys, much appreciated. Seems like it's mixed feelings on the success of the unit, and since we spend a lot of time upstairs, that would defeat the point.
    Glad to hear the manufacturer knows what they are talking about.
    A separate attic unit is clearly not an option.

    There is a return to the attic furnace in the center of upstairs hallway ceiling that bedrooms break off to, so I guess if humidity makes it's way up there, then it should still get into the bedrooms with doors closed.
    Thankfully bedroom doors are rarely closed (no kids) as we have cats and they will scratch at the door so it's easier to leave open.

    There's a fairly substantial 'column' (maybe 2.5ft wide) that goes from the utility room in the basement (where the 800 would be located) in a straight shoot all the way to the attic - it's for the hot water heater vent, which is a high efficiency heater that doesn't seem to have hot exhaust gas as the metal duct is fairly cold to the touch about 5 ft from the heater. We always wondered what certain wall shaped in the house were 'concealing'.
    It's entirely possible that a new single supply duct (4" or 5" solid aluminum round for more pressure to that line to allow forced air to travel up there, or perhaps a similar flexible duct material) could run in there as a new supply from the main furnace to a new vent that could supply humidity from a new vent in the upstairs hallway wall?
    No walls would need to be ripped out and since this 'column' is inside the middle of the house, it would not suffer from cold as we keep a steady 72F all year round
    Could an 'in-line' vent fan help with moving the humid air from the main furnace up there? If such a thing exists?

    That could potentially solve this issue, or at least make the upstairs bedroom floor more humid than just relying on humidity 'rising' from supply vents on the main floor?
    If this space is large enough to fit a supply line, would this be a possible solution?

    Appreciate feedback.

  8. #8
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    I would see how the humidity is after the 800 is in for a week. Before trying other ways.

    Making a duct small that runs up to the hallway would defeat its purpose. As it would decrease the amount of air going to the hallway.
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  9. #9
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    Quote Originally Posted by beenthere View Post
    I would see how the humidity is after the 800 is in for a week. Before trying other ways.

    Making a duct small that runs up to the hallway would defeat its purpose. As it would decrease the amount of air going to the hallway.
    Thanks for the response.
    Might be worth having the 800 installed and seeing how it goes as you say.

    Not sure I understand why running a new supply line from the main furnace to the upstairs hallway to directly supply humid air to the part of the house that's most difficult to reach from the forced air coming out on the main level 15ft below the upstairs would "defeat the point"?
    I was thinking this new supply line would come directly from the furnace, not added to the main supply trunk line that feeds all the other supply vents on the main level of the house.

    In fact, perhaps the new line would be better on the return, since humid air would be there, and no impact on pressure from the supply line if I use an in-line fan?
    I've found there are in-line duct fans with variable fan speeds that also have probes that can run inside the duct to measure humidity and control the in-line fan speed appropriately, that could ensure humid air is sent to the upstairs floor via this new supply line.
    Would an additional 4" duct with controlled supply pressure (in line fan) really have a major impact on robbing air from the furnace blower and the main supply line?

    I'm trying to get the moisture upstairs without having to start putting portable units in every bedroom, since an attic unit it not an option unless we have the attic 'conditioned' which would be a very expensive job.

  10. #10
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    Looking at the wiring, the 800 unit only requires 10-2 since the neutral is not used.
    Is there any point in spending extra to run 10-3 and connect neutral to the breaker panel when it's not used for the 800 and would need to be capped off?

  11. #11
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    Also, the 800 dispersion tube cannot be installed in the vertical section of the furnace as there's no duct above the AC coil unit?
    Installer says it should be ok if the dispersion tube is installed vertically up through the bottom of the horizontal supply duct (you can see in the picture the area he's talking about putting the dispersion tube which had a cut-out for annual duct cleaning).
    Is this ok?

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  12. #12
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    15 foot vertical rise is not all that much. Using a small duct to force it up is counter productive compared to using a larger duct. Don't forget, that if the basement furnce runs and the second floor furnace isn't running. Then the humidity you add can flow into the duct in the attic, and condensate in the duct.

    In the bottom of the horizontal duct should be fine.

    See how the RH is with just the 800 installed first before doing anything else.
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  13. #13
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    Thank you for the reply!
    Now just to make a decision.....really hope that the upstairs is at least a little more comfortable, as in a little humidity gets up there

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