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  1. #1
    Join Date
    Mar 2008
    Posts
    13

    Whole House Humidifier in AC System Only

    We have an old house with hot water heat. About 3 years ago, we retrofitted the house with central air. Now we want a whole house humidifier and our AC company is saying they can install a humidifier in the attic with our AC unit and it would work because we run our fan 24/7 in the winter.

    They said, it might mean we need to clean the vents more frequently, say every 3 years, they also said we'd need to insulate the unit in the attic to avoid freezing.

    Does this seem feasible? We really need a whole house unit as the kids just hack in the dry heat during the winter.

    Thanks!

    Speziak

  2. #2
    Join Date
    May 2006
    Location
    Philadelphia, PA
    Posts
    1,379
    Yes it is feasible. Depending on attic construction it may need to be insulated and the water line and drain heat traced. I recomend a steam type humidifier. I find them to operate better when the air is not heated.

    One option to have your contractor look into is the new Honeywell Tru-Steam humidifier. It has an option to be remote mounted and the steam can be injected into the ductwork up to (I think) 20' away. As of 3 wks ago delivery dates are still up in the air, but I'm sure it would be available to be installed before next heating season.
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  3. #3
    Join Date
    Mar 2008
    Posts
    13

    Honeywell Steam Unit

    Thanks very much for your reply. So there are no worries about condensation in the vents since there will be no heat in those vents? The attic is not insulated, except for the floor. Could we insulate the pipes?

    Thanks!

    Speziak

  4. #4
    Join Date
    Mar 2008
    Location
    Maryland
    Posts
    11
    Like comfort doc said, the honeywell that can be remote mounted would probably be your best bet. Steam is definatley the way to go.

  5. #5
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,875
    Check the temp of the air coming out of those vents before you put install a stream humidifier.

    The remote mount is ok. But, you still could have moisture condensing in the ducts if the ducts are losing too much heat to the attic.
    If it condenses in the ductwork, you will end up with mold issues.
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  6. #6
    Join Date
    Apr 2004
    Posts
    420
    Condensation will form not due to heat, but because of the lack thereof in the ducts. Cooler air holds less water, thus if the air which is currently blowing out of your registers in the winter (that's why beenthere suggests recording this temp) suffers enough heat loss in it path through your attic ducts and thereby drops below the dew point, the steam will condense in part before terminating into your conditioned space. You can check the delta by measuring the air temp at the return and at the furthest supply outlet to see the heat loss incurred with your own eyes. The better the attic ducts themselves are insulated/sealed, the lower the heat loss and the lower the chance of condensation being a problem.

    Why not a stand alone unit like the Aprilaire 350 or 360 series set up and ducted from your basement or elsewhere in a more conditioned environment? Just needs a short 7'' duct run to the living area. Unless you super insulate (and seal) the A/C ducts, you will probably have steam condensing within them in the cold winter-y attic. Sure, most of the water quantity will reach the living space but IMHO it's a bit risky: You have to imagine the cumulative effect of condensing water over the course of years. Disaster immediately?--no, not if installed conscientiously. But down the line, who's to say?
    Last edited by drcustom; 03-24-2008 at 08:25 AM.

  7. #7
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,317
    Quote Originally Posted by speziak View Post
    We have an old house with hot water heat. About 3 years ago, we retrofitted the house with central air. Now we want a whole house humidifier and our AC company is saying they can install a humidifier in the attic with our AC unit and it would work because we run our fan 24/7 in the winter.

    We really need a whole house unit as the kids just hack in the dry heat during the winter.
    Running your indoor blower 24/7 with ductwork in the attic is likely contributing to your low indoor humidity levels. Low interior humidity levels are typically caused by too much outdoor air getting into the house, overwhelming what amount of natural interior humidity generation is available (cooking, showering, laundry, etc.) with cold, dry, outdoor air.

    If ducts in an attic are leaky, and they most often are, by running the blower around the clock you are pushing air in your house up into the attic. You cannot lose air to the outside of your house (an attic space is considered, in a sense, "outdoors", since you do not heat or cool it) without needing to make it up somewhere else. Leaky windows, doors, and other gaps in construction are the usual culprits for cold, dry outdoor air sneaking in to make up for what you lost to the attic.

    What is the reason you run your blower 24/7? For more even room to room temperatures?

  8. #8
    Join Date
    Mar 2008
    Posts
    13

    Honeywell Tru-Steam

    Hi,

    A few questions about the tru steam. Which specific model number would it be? Would it need to be mounted in the attic and would it potentially freeze in ultra cold temps?

    Is there a puddle of stagnant water when the unit is not in use?

    Thanks!

    Jon

  9. #9
    Join Date
    Sep 2007
    Location
    North Carolina
    Posts
    48
    Just curious, have you measured the humidity in the home with a good quality gauge?
    I am not talking about the wall-mart brand humidity indicator.

    Are you sure the hacking is not being caused by allergies?

    I have seen some folks screaming about the low humidity in their home only to find it was an issue with the way it was measured (incorrectly) with a cheap gauge.

    Then they began addressing the dust and allergy issues for relief from their symptoms.

    Running the blower upstairs can be a bad thing. Cost you money, causes more infiltration of outdoor air which can bring dust and air with lower humidity into the home.

  10. #10
    Join Date
    Mar 2008
    Posts
    13
    Yes, we have tested the humidity and I wish I could remember exactly what it said, but in the two gauges we had (they each came with humidifiers) the humidity was well out of the 'comfortable' or 'acceptable' range.
    We run the fan all the time because it has a HEPA filter in it, that's okay, no? I thought that was advised.

    As for allergies, etc. we don't really have those sort of problems, but we all get that awful dry mouth from these cast iron radiators in all of our rooms!

    I'm certain it is a humidity issue. It's more discomfort than anything else but why put up with that?

    Also, our local AC person has said that the price of operating the Honeywell True Steam would be quite high. He also mentioned that there would be stagnant water in the pan when not used. He felt that there were other options that would work just as well that would not cost anything additional in electrical and would have no pan.

    Does that make sense?

    Thanks!

    Jon

  11. #11
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,875
    Infiltration is causing your low humidity. If you address infitration, you'll help minimize the humidity problem.

    Any humidifier you install in an attic, is at risk of freezing.
    Steamers will show a rise in your electric bill, but they will increase the humidity.
    They can add moisture to the air, even when the stat isn't calling for heat.


    The True Steam, purges itself. The purge time can be adjusted.
    Doubtfull the water will sit in it long enough to become stagnet.
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  12. #12
    Join Date
    Mar 2008
    Posts
    13
    I called our AC person and he is recommending an Aprilaire 400. He claims for our needs this is the way to go. I told him about steam, we discussed the freezing issue and he seemed to think it would most likely not happen except under extreme circumstances. He said, "I can get anything" I just think it's going to cost you a fortune to run.

    Now I am TOTALLY confused

    Thanks for your time.

    Speziak

  13. #13
    Join Date
    Sep 2007
    Location
    North Carolina
    Posts
    48
    I wish you the best with the humidifier.
    I cannot advise you as to which brand would work best for your application.
    Our company does not install humidifiers in attics. We have other options.

    As far as running the fan, you need to be very sure that your duct is well sealed and not leaking. There may be a secondary drain connection coming off the indoor unit. Check this and be sure it is not left open (or plugged for that matter).
    If left open it will cause you to loose air. We install float controls on all our secondary connections to stop leaks and stop the unit in the event of a main drain blockage.

    Im not saying it is a bad thing but why are you using a HEPA filter if you do not have allergies? Just curious I have to ask. Dust? Just feels like the right thing?

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