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  1. #1

    Two zones = two humidifiers?

    I've got a 20yr old 2 story house with basement. Probably over 4,000sf with the finished basement. I've got two high efficiency natural gas heaters, but unlike most setups, they are not dedicated to the first and second floors.... instead they split the house side by side.

    I don't know how 'tight' the house is really. Newer double pane windows and sliding doors. Replaced the weather stripping around my drafty front door before winter hit. Attic has one of those insulated zippered covers over the ladder. Nothing seems drafty, but who knows how well sealed things like recessed lights are.

    Anyway, what I do know is that my house is dry, at least it seems like it. My wife and son have been getting nosebleeds, my skin is crazy-dry.

    So, my questions....
    1. Is there an inexpensive device for measuring humidity? I don't want to spend $80 on some professional tool that is accurate to .1 %. I'd spend $14 to get within a 1% or 2%.

    2. Should I be looking at a whole house humidifier solution? There is an OLD Aprilaire unit on the RIGHT side blower, but none on the left. It doesn't appear to be working and was last serviced in 2003 (we bought in 2011 and installed 2 new complete HVAC units - blower, coils and condenser).

    3. Because of the configuration of the LEFT blower, it may not be possible to mount a bypass or powered unit on either supply or return (which is probably why there's a humidistat mounted but no humidifier). Can a single humidifier unit be mounted on the RIGHT side unit and function for the whole house?

    I'm sure I'll have follow-up questions.... but thanks in advance.

    -Tim

    [Southeastern PA, 2 story house, walkout finished basement, wood frame, stucco exterior, Attic. Built 1992]

  2. #2
    Join Date
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    You can buy a cheap hygrometer in the price range you're looking at. If you leave both furnaces' fans running constantly (during the winter only), it will help disperse the humidity if you only have a humidifier on the right side unit. If your systems haven't been serviced in 8+ years, they need to be. At that time, they can look at the humidifier and replace the water panel.

  3. #3
    Join Date
    Dec 2010
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    You mentioned that there are humidistats (already) on the furnaces......they should be able to tell you the humidity level in your home. Test them against each other. Normally, they are pretty accurate.

    Because your systems are designed to heat both levels (which to me is a weird design, where are the thermostats?), you need to find a way to get another humidifier on the other furnace. Besides, that old AprilAire will do only about 2,800 s.f. when operational.

    You might as well have 2 new modern (with outdoor sensors) humidifiers installed.

  4. #4
    Join Date
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    Unless the house is spray foamed and really, really tight, I don't think you'll need one upstairs. Stack effect will draw warm humidified air from downstairs, to the upstairs, along with normal diffusion. Add in that upstairs has bathrooms which a the largest moisture laods in a hoem next to the kitchen and I doubt you'll need it. Do some measuring first. PN my home at least FWIW, the upstairs runs 3-5% RH higher than downstairs and i ony have a bypass humidifier on the downstairs furnace. MY air leakage I estimate is around average to above average. Probably about the same as an average mid 90's home.

    On the flip side, upstairs can benefit form dehumidification in summer, whereas the downstairs won't need it as much.

  5. #5
    Yeah, I don't know why they designed the house this way originally, but the two units each heat a different side of the house. The RIGHT unit has its T-stat in the dining room, the LEFT unit has its T-stat in the family room. With the large open foyer there should be plenty of circulation between the floors. The whole downstairs is fairly open as well, and the only doors that really get shut are the three RIGHT bedroom doors which are closed at night. The basement has two vents, one off of each blower.

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    The heaters, blowers, coils and condensers were all installed new in the summer of 2011 when we moved in. The old Aprilaire unit appears to be very old and not working and the last time the pad was changed according to the writing on the ductwork, is 2003.

  6. #6
    Join Date
    Dec 2010
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    If the basement is unfinished, I think it would be pretty simple to correct the "zone" layout. I do not see a reason for splitting the systems from left to right verse up and down. Odd.

    I've seen it only once and it didn't work for the customer then either. I took his two systems and went to one. But his home was smaller.

  7. #7
    Quote Originally Posted by George2 View Post
    If the basement is unfinished, I think it would be pretty simple to correct the "zone" layout. I do not see a reason for splitting the systems from left to right verse up and down. Odd.

    I've seen it only once and it didn't work for the customer then either. I took his two systems and went to one. But his home was smaller.
    George,
    The basement is actually finished though its a drop ceiling, but I don't think it'd be an easy conversion either way. For the 1st floor, yes you could service all of the registers with some modification to the existing ductwork. However, all of the rooms have the registers in the floors so I don't think there is any way to combine the runs on the second floor. Maybe if the 2nd floor had the ductwork in the attic with ceiling registers...but I think you'd have to take out a lot of drywall and make a mess of the 1st floor to combine the 2nd floor ducts.



    My other concern is whether its even practical to use a bypass humidifier given the limitation on access to the supply side. For the LEFT side unit, They'd have to mount the humidifier on the Return side and then bring the bypass duct around and then into the front or possibly even the opposite side of the supply (see diagram option 2). The reason is that the supply does an immediate 90 coming forward out of the top the blower. The Right side unit is a little better but it would still have to be mounted on the side of the return and then run the bypass duct to the front of the supply side (like option 1). I guess my concern is with how much of an affect the added distance and 90's would have on the airflow through the bypass? I was considering going with two Aprilaire 400's, but perhaps a remote mounted steam humidifier is more practical?

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  8. #8
    Join Date
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    If there is access to the supplies in the basement, it would be an easy process to change the systems to a (much better) up/down situation. There is no need to get into the sheetrock or to move registers. All the work would be in the basement.

    I just thought of another possibility......you could zone the current systems so that you would have a thermostat upstairs as well as the existing thermostats downstairs. The person I dealt with (also with 2 systems) had the same setup as yours and he could not A/C the second floor because the thermostats were on the first floor.

    As far as the humidifiers are concerned, the length and/or the elbows of the by-pass pipe does not effect the performance of the humidifiers.

  9. #9
    I assume the cost of switching to an up/down zoning would just be the cost of the ~ 40ft of ductwork and labor to reroute it in the basement. Any ballpark on the cost? $500, $1000? Also, you'd probably relocate one T-stat to the 2nd floor I would assume.

    I think that would be ideal, though I don't know whether it is worth doing at this time. Aside from the dryness, we don't have any issues with the HVAC. Since both Thermostats are on the 1st floor I would guess its always warmer upstairs. Certainly not ideal, but not really an issue for us. I think the only "issue", and its really not a problem, is that the kids all sleep with their doors shut so their rooms tend to be a little cooler.

  10. #10
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    Just a idea to think about if you're not able to cool the 2nd floor. I got off the subject, sorry.

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