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Thread: installing a furnace type whole house humidifier

  1. #1
    DIY Junior Member jessel's Avatar
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    Default installing a furnace type whole house humidifier

    Hello,

    I'm feeling like I need a humdifier. The house has forced hot air, though I primarily heat with a wood stove. I've started looking around online and I see that there are two type of humidifiers out there: steam and evaporative. It looks like either type is available as an add-on to an existing furnace. I'm thinking that the evaporative humidifier looks like a it would do the job, and I'm inclined to get one as the price is much lower. I can see pricing, features, but I don't understand the motivation to get the more expensive steam humidifier. I would guess that a steam humdifier would be more expensive to operate too.

    So, given that I'm looking to get the evaporative humdifier, is it reasonable for a homeowner to install it? Looking a the installation instructions I'm thinking it looks pretty straightforward.

    I'm wondering if a compatible relay should be installed or if I would a "sail switch"? My furnace (model: NUGG100EA02) does not have fan relay to operate blower only. In my looking around, I've found that the Honeywell HE360A, can be purchased with an installation kit that includes a sail switch.

    Any comments will be appreciated,

    Thanks in advance

    Jesse

  2. #2
    DIY Senior Member SteveW's Avatar
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    I have the Trane-branded version of the Aprilaire 600 evaporative humidifier and it works pretty well. Very simple, low maintenance. On down side, it does "waste" a lot of water due to being designed to continuously flush itself to keep from getting gunked up with deposits. Also it gets my house up to about 35% relative humidity (RH) - and sometimes I'd like to see it a little higher.

    For a while I had a different type of humidifier that had rotating plastic discs that dipped into a water reservoir, and air blew over the tops of the discs. Seemed to be a little more effective but the reservoir would get mold after a while.

    I have thought about a steam unit but they are expensive and at least the initial versions had a lot of problems as I have read on another list. I think one of the advantages of steam is that is can get more water into the air than evaporative units, especially if you have a heat pump -- heat pumps put out cooler air than gas furnaces so it is harder to get water to evaporate.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    My brother-in-law, a mechanical engineer, installed one of these in his home and has been satisfied with it: http://www.desertspringproducts.com/...ers_rotary.asp.

    I have an AprilAire unit in mine. One thing to consider, if your interior air humidity level is low in the winter, you likely have too many air leaks in the house. In a tight house, you might end up with too much humidity, and need to vent the house via a HRVS. That being said, you also want to utilize an outside temp sensor with it (optional on some, standard on others) to adjust the humidity level (lower when really cold outside, and higher when warmer) and, as a second benefit, it shuts the system down when it gets above about 50-degrees. If you let the humidity get too high when really cold outside, you risk condensation and potentially mold from that moisture behind things that don't get good ventillation.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Senior Member SteveW's Avatar
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    I agree with everything Jim says -- esp the part of definitely using a smart system that monitors outside air temp. I have read of way too many folks (on a piano forum I go to) that really want to keep their homes' RH at a constant 45% year round. That may be OK if outside air temp doesn't get below 40 F or so - but not OK if temps get too low and water condenses in your walls.

    Yep, Desert Spring was the one I had. Bought it at one of the "big box" stores and installed it myself. An HVAC service guy persuaded my wife to replace it with an Aprilaire - but if it were up to me I would have kept it. I think it worked very well. I added a kit that flushed the reservoir every 24 hours and would recommend that it be used.

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    DIY Senior Member SteveW's Avatar
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    RE: need for sail switch, etc --
    if no one on this list answers your questions, check out this other list that I check on from time to time:

    http://www.************.com/forum/hu...midifiers-130/

    They have HVAC pros answer technical questions, much like Terry and other professional plumbers do for plumbing questions on this list.


    ------------------------------------

    EDIT: for some reason every time I try to give the link it gets turned into asterisks. It is a do it yourself site (that's the name).
    Last edited by SteveW; 12-01-2012 at 08:51 PM.

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    DIY Junior Member jessel's Avatar
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    Hey all,

    Thanks for the responses. The desert air system looks like it would work, but I'm thinking that the aprilair 600 would too. I will let you know what I decide on, I'm really not sure at this point. I do plan to get something on order this evening, but I have some running around to do today.

    I think I was way off about the sail switch, and that the relay installation is necessary. I'll take a look at the other forum, but a relay is just a switch and I think its covered in the furnace installation manual.

    Does this type of humidifer operate well while the furnace is in blower only mode? I really don't run the furnace much. I've got at least 5 cords of wood piled up outside!

  7. #7
    DIY Senior Member SteveW's Avatar
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    As far as I know, really only a steam unit will work very effectively for blower-only mode. You really need warm air going over the evaporative pads or the discs to get the water to "want" to do a phase change and go from liquid to vapor. Again, the "other" site may give you some add'l info from the HVAC pros -- I do know that they discuss steam units pretty often so I am thinking that there are a lot of folks not satisfied with the performance of evaporative units.

  8. #8
    Retired Defense Industry Engineer jadnashua's Avatar
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    A steam unit is very maintenance heavy and electrical energy hog...if you're water is at all hard, the mineral deposits will clog things up and require cleaning regularly. An evaporative unit still needs some maintenane, but usually all it takes is replacing the filter/wick and brush the thing out. On most of the evaporative humidifiers, they'll produce a fair amount of humidity with just moving the air across them. True, you'll get more if the air is heated, but you'll still get a fair amount. The evaporative systems does slightly cool the airstream down...a steam system often won't. You pay for that energy one way or the other -either in heating the air more or heating the water (to boiling), so it's probably a wash.

    An evaporative unit is simpler - often only an electronic sensor (also needed with a steam unit), and a solonoid valve to turn the water on and off. Some get more complicated, like adding a clock motor to turn the pad and maybe a backwash timer/system. A steam system would need some additional safety circuits.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Junior Member jessel's Avatar
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    I just ordered the aprilaire 600, the reviews on amazon were much better than the desertsprings. While I was seriously considering the desertsprings model the basic design looks good, however the price was higher. I would have wanted to get the autoflush (a separate item), and I'd need to get the humidistat separately too.

    I've got to think that the 600 model will do ok for me with the blower only, but it may be that I'll have to run the furnace some too. Thats ok, the price difference to the steam unit will but quite a bit of propane.

    I guess one of my concerns with a steam unit was the power usage, but I didn't realize there could be more maintence issues with them. I was initially put off by the high price tag.

    Well, I'll post a picture, and let you know how the install goes.

  10. #10
    DIY Senior Member SteveW's Avatar
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    The pros on the other site I have mentioned recommend plumbing the water supply to a HOT water source to increase the effectiveness, esp if the air across the pad is on the low side as it will be if you use the blower only. I did this myself. Aprilaire is OK with the practice as well and if I recall they also recommend it.

  11. #11
    DIY Junior Member jessel's Avatar
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    They do recommend this, it is in the manual. I will do this, only issue is that with my on demand hot water it takes two or three minutes to get hot water. The minimum to trigger hot water is 1gpm and I have a well that is rated for 5gpm. So, the humidifier won't get hot water unless some other appliance dishwasher, washing machine is drawing hot water. I've actually considered putting in a small electric hot water tank so it'll be hot immediately, but thats another matter altogether.

  12. #12
    Retired Defense Industry Engineer jadnashua's Avatar
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    I don't think the difference is enough using hot water to justify the cost of having to add a supplemental heating device for that. Then, your results may differ. Mine seems to work fine using just cold - could it work better with hot, maybe, but it's good enough without.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  13. #13
    In the trades Dana's Avatar
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    Quote Originally Posted by SteveW View Post
    I agree with everything Jim says -- esp the part of definitely using a smart system that monitors outside air temp. I have read of way too many folks (on a piano forum I go to) that really want to keep their homes' RH at a constant 45% year round. That may be OK if outside air temp doesn't get below 40 F or so - but not OK if temps get too low and water condenses in your walls.

    Yep, Desert Spring was the one I had. Bought it at one of the "big box" stores and installed it myself. An HVAC service guy persuaded my wife to replace it with an Aprilaire - but if it were up to me I would have kept it. I think it worked very well. I added a kit that flushed the reservoir every 24 hours and would recommend that it be used.
    Keeping it that humid indoors year round could lead to a MOLD DISASTER, depending on the wall stackup. The dew point of 45%RH/70F air is 48F, which means any wood or paper in the wall structure that spends more of it's time below 48F than above 48F during the winter will be adsorbing conditioned space moisture BIG TIME.

    If the wall has a poly vapor retarder on the interior side of the insulation and ABSOLUTELY NO AIR LEAKS to the interior space (no picture-hanger holes, no leakage around electricl & plumbing penetrations, etc) you can keep it that high. Or, if the place has sufficient insulation outside the structural sheathing that the mean temperature at the sheathing in January is above 48F (not likely) you'd be safe.

    If you air seal a house to meet the IRC 2012 standard (3 air exchanges per hour at 50 pascals) you'll never drop below 30% RH @ 70F in NH without active ventilation, eliminating the rationale for the humidifier. You may need to actively ventilate to keep it below 35% RH @ 70F, which is the highest you'd want to let it drift to in January.

    Leaking ducts & air handlers on hot air heating systems will create pressure differentials between rooms that use the "great outdoors" as part of the return path- an unintended ventilation that leads to drier winter air and higher heating bills. Air seal the house, but air seal the ducts too.

    For remediating natural stack-effect infiltration it pays to treat both the top and the bottom of the stack. Foam sealing all of the electrical, plumbing, & flue penetrations into the attic can be a time consuming process fraught with missed spots, but do what you can. In the basement the biggest non-obvious air leak is usually the foundation sill and band joist, which typically adds up to more leakage than all the windows & doors in the house combined. If you have a lot of air sealing to do you might spring for some 12 board foot FrothPaks (at the big box store home centers.) Around flues you'd have to use sheet metal, and seal the seams with stove-cement or an automotive muffler-sealer type product, but good quality acrylic caulk and 1-part can foam can do the bulk of it. Recessed can lights that penetrate the upper floor ceiling are a real PITA, but you can box-over them with cardboard if you allow 3" clearance- tape the seams with housewrap tape, and seal the box to the gypsum with caulk or foam. Don't forget the dryer vent backflow preventer- most are pretty sucky, and look for any plumbing or flue chases (or balloon framing) that runs from the basement to the attic, and seal it ALL! Then you can chase the diddly on the intervening floors, but it's not nearly as important as the basement and attic leakage.

    It's pretty difficult to air seal to the point where you'd need active ventilation for indoor air quality, but if you get it tight enough that it's over 35% RH @ 70F in January you should check for backdrafting issues with the woodstove or other atmospheric drafted appliances when the dryer and kitchen/bath fans are all running. If that becomes an issue, some woodstoves have outdoor combustion air kits that can be retrofitted (and would be recommended whether it's a tight house or not.) If you have an atmoshperic drafted water heater that backdrafts when it's all going you may need to judiciously create a vent somewhere on the first or second floor- somewhere near the "neutral plane" of the stack effect forces.

    Dry air sucks, but humidifiers are often a "solution-problem", trading wintertiime comfort for some earlier-than-pollen-season allergy symptoms (or worse) from the mold that's eating your house from the inside out.

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    DIY Junior Member jessel's Avatar
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    I got the humidifier on Wednesday, not bad for free super saver shipping and an order placed on Sunday night! But it sat in the box until this afternoon.

    At this point I'm only partway through the install. I got the cutout in the hot air plenum and the unit is mounted, but I need to pick up a piece of trunk line as my 6X22 return air register is connected to the return line by just two 6" dia rounds. I'm going to see what I can get my hands on at the local box store as far as a bigger line. Seems to me that 8 x 14 would be more appropriate, but I'm not sure what the standard sizes are as I'm betting I won't actually find this at the big box stores (since their online inventory is pretty accurate).

    I do need to add a relay to actuate the blower as well.

    jadnashua:
    I wasn't going to get a hot water tank for this, I just get irritated at my on demand water heater taking so long to produce hot water. I'm unlikely to ever change anything, because in reality the on demand hot water works fine and its expensive to mess with the plumbing system so I won't do it unless there is a real need to.

    Dana:
    I hear what you're saying and I considered these or similar issues before buying. My house is fairly new, the air leaks that I have are going to be more expensive to fix, and overall the house is fairly tight, and (the wife) and I want a solution now. I don't plan to run it 24 x 7, and so this unit to me makes the most sense because any humdifier will be more masking of symptoms than fixing the problem. This is a fairly simple unit, and its inexpensive.

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    DIY Junior Member Failure2Comply's Avatar
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    Since you primarily heat with wood an evaporative humidifier such as an Aprilaire 600 Bypass humidifier will not work to meet your needs. You need a steam humidifier such as a Honeywell. It will be able to turn on your system fan while it is humidifying regardless of whether your heating system is running.

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