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  1. #14
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,189
    yes, every installation guide states that a trap is required, nearest the unit is preferred.
    as stated - size is depth of p-trap=static pressure.
    review the installation guide that comes with the unit and configeration you have selected, most are online.

    your lifestyle is the guiding factor.
    if you live as you state, then the air exchanger would not be as important.
    I would add the fresh duct to the ac return with a filter near the intake to keep the air and this duct clean.
    this is not an expensive item. in your climate this ductwork would need to be insulated.

    this fresh air install will keep your home under positive pressure,
    as the ac install will keep your coil under a positive pressure.

    best of luck.
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  2. #15
    Join Date
    Aug 2013
    Posts
    61
    Thank you so much for your response. This is all very helpful.

    Interesting thought about a fresh air duct keeping the house under positive pressure. I will consider that. The main reason we were avoiding a fresh air duct is that we live near to some pretty serious agriculture, and are dealing with some pretty serious allergies as well, and even though filters can filter a lot out, they are not perfect. We thought it made more sense to keep control over what comes in our house by just opening the windows when conditions were good for it (like after a rain, etc.).

    Also, you said in an earlier post to consider a variable gas furnace (which was our plan) and lower the bonnet sensor for the fan to come on at a lower temp. You said most are set at 165, set at 145 for the softer heat. I did not realize there were options like this and for comfort, this sounds like a good idea. Could you elaborate on this?

    We have decided at this point NOT to go with a heat pump (per my concerns on this thread about mold), and just go for a two stage AC (probably Carrier Infinity). However by doing this, we do lose the softer heat in the winter that a heat pump provides, so I am intrigued by your suggestion here. I never even heard of a bonnet sensor. So I would appreciate your elaborating on your suggestion here; it sounds like it will alleviate this issue. Thanks!

  3. #16
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,455
    Quote Originally Posted by ndeverest View Post
    Do you need a trap if the coil is under positive pressure? I am under the impression that this is optional when under positive pressure, especially if the condensate line drains into a utility room (which our new system will). In this case the lack of a trap is really just like a small leak in the system, but there will be a number of turns in the condensate line between the unit and the drain so this will be minimal. And also, it will be heating/cooling conditioned space anyway so a small "leak" is not a big deal. And then not having a trap will insure there are no drainage problems caused by the trap.

    I do understand that if the coil is under negative pressure that a trap is mandatory. But we will be under positive pressure.

    We were not planning to install a fresh air exchanger. Unlike most people though, we do open our windows and air the entire house out every week or so, even in the winter. As long as we do this, do you think a fresh air exchanger is still something that you think is important to have?

    As far as Chinese drywall is concerned, we did not notice any problem on any metals anywhere else in the house. That's why we didn't think this was the culprit.
    Concerned consumers like you are few. Indoor air quality starts with a fresh filtered air change every 4-5 hours when the home is occupied. It is needed to purge indoor pollutants and renew oxygen. Most leak enough naturally during very cold, windy weather that you do not need mechanical ventilation. Yet during calm mild weather with closed windows, the same home only get an air change in 12-24 hours. You can confirm this by monitoring the outdoor dew points to the indoor dew points. Currently the out dew points in NE are 30^F. If your home is getting the needed air change in 4-5 hours, your homes indoor dew point is currently declining significantly.
    When spring get here with higher outdoor dew points, your indoor dew points rise rapidly. When the oudoor dew points are +65^F, plus the moisture from the occupants, the indoor dew points will be high enough to have 70%RH indoor without any cooling load. A few days of this and basements smell like basements and dust mites are awaking from their winter nap. The a/c is running. During day of rainy weather that is needed to grow corn, your a/c is not running and the %RH is risiing. Everything is damp if you are getting adequate air change. Yes you are pretty much dry but mold will grow in any place where you are near saturation for several days.
    You need mechanical fresh air ventilation when occupied and supplemental humidity control to maintain <50%RH throughout the home and ducts. I realize that a/c needs to cold and damp for many hours everyday, your a/c system should be dried everyday for several hours to assure control of bacteria and mold growth.
    Must go. Glad to discuss more if you are interested. Post issues.
    Regards TB
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  4. #17
    Join Date
    Nov 2006
    Location
    Athens, Ohio
    Posts
    1,817
    Something I have not seen in the posts so far - was the fan/coil sloped for proper draining?
    Re. positive or negative coil pressure - water runs off the coil because of gravity. If static pressure and velocity in the system is correct then it should not matter if the coil is before or after the blower.

  5. #18
    Join Date
    Aug 2013
    Posts
    61
    Teddy Bear,

    I assume when you say concerned consumers like me are few that this is a compliment! I really didn't intend to learn this much; it was kind of forced upon me by the mold problem explained at the beginning of the thread. And now that I realize how complex HVAC stuff is, I realize what you already know... not all HVAC contractors practice their trade at the level that most people on this forum do. That's why I came here.

    Anyway, we just decided to not only follow your advice and install a dehumidifier but also add a fresh air intake. It seems a bit counterintuitive that having a fresh air intake during the summer would keep RH down; it seems like it would increase it (because it is humid outside). But if we have a dehumidifier then this is not as much of a concern. And I do see the benefit of it. I teach math for a living and your argument is very logical. A math teacher can't argue with logic!

    We will just be sure that we have a way to totally cap the fresh air intake (from the outside) during those times when we don't want air coming in from the outside (like during certain times when the neighbor is cutting his crops). Then threis no downside to it.

    Under your "Bear Rules" you say "and keep windows dry during cold weather." Are you saying that this is something we should specifically do, or do you mean that by HAVING a fresh air intake this will have the EFFECT of keeping the windows dry during warm weather. Please clarify this.

    In the winter we tried a whole house humidifier (honeywell, I think) but the grill (or whatever you call it) that the water runs down really started to stink after awhile (like just a few weeks), and it turned all green like mold. We ended up just bypassing the humidifier and boiling water. But this certainly is a hassle. Do you have any comment on this?

    Thanks again!

  6. #19
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,455
    Quote Originally Posted by ndeverest View Post
    Teddy Bear,

    Anyway, we just decided to not only follow your advice and install a dehumidifier but also add a fresh air intake. It seems a bit counterintuitive that having a fresh air intake during the summer would keep RH down; it seems like it would increase it (because it is humid outside). But if we have a dehumidifier then this is not as much of a concern. And I do see the benefit of it. I teach math for a living and your argument is very logical. A math teacher can't argue with logic!

    We will just be sure that we have a way to totally cap the fresh air intake (from the outside) during those times when we don't want air coming in from the outside (like during certain times when the neighbor is cutting his crops). Then threis no downside to it.

    Under your "Bear Rules" you say "and keep windows dry during cold weather." Are you saying that this is something we should specifically do, or do you mean that by HAVING a fresh air intake this will have the EFFECT of keeping the windows dry during warm weather. Please clarify this.

    In the winter we tried a whole house humidifier (honeywell, I think) but the grill (or whatever you call it) that the water runs down really started to stink after awhile (like just a few weeks), and it turned all green like mold. We ended up just bypassing the humidifier and boiling water. But this certainly is a hassle. Do you have any comment on this?

    Thanks again!
    It is a compliment.
    The Ultra-Aire DEH3000 controller has a damper option that provides a electric damper for the fresh air inlet. You can set up a timer to routinely operate the electric damper that controls fresh air. Also the controller allows manual operation of the damper. Remember all the air in your home comes from outside and passes through your home. If there are pollutants outside, they will infiltrate your home. For these cases, you might consider adding active charcoal as part of the filters.
    Regarding windows, yes only humidify to points that you see minor moisture on the insides of the windows. If you windows sweat without humidification, increase the ventilation rate of the dry outside air. Sweating windows are a sign of excess moisture in the home or a lack of adequate fresh air ventilation.
    Talking about humidifiers, most home with an air change in 4-5 hours will need some humidification. Whole house humidifiers need enough water overflow to prevent any mold/bacterial growth. The overflow flushes the biological down the drain. Also several hours of dry humidifiers or cooling coils each day reduces potiential for biological to grow. Boiling water is ok but energy intensive.
    keep us posted.
    regards TB
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  7. #20
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,189
    for the agriculture conditons use a serious filter. such as a 4" thick ( MERV 11 ) vs a standard 1" (MERV 6)and oversize this filter would require fewer changes.
    upsize to a standard size filter. example 11"x11"x1" costs $- as a 16"x16" x 4" costs $. ask what size is standard for your area and its costs.

    there are misting and/or steam humidifers that resolve the trickle down water problems.

    let's review a gas furnace operation. t-stat calls for heat and sends low voltage to open gas valve. igniter coil lites the gas and heat warms the heat exchanger. there are many types of exchangers. all exchanges are sealed where the condition air is separated from the gas and its combustion products.
    when the bonnet sensor -name may vary by manufactor but called a bonnet senor cause its located near the top of exchanger, reaches about 165 degrees this sensor tells the fan to come on.
    thus warm air arrives in home.
    t-stat is satisfied and gas valve closes. the heat exchanger cools to 125 and sensor turns off blower.

    this bonnet sensor temps can be lowered manually or if fixed by manufactor your dealer can order this sensor to turn on at 145 and off at 110
    air at 110 may feel cool cause its fan assisted.

    better questions=knowledgeable consumer
    Last edited by beenthere; 10-22-2013 at 08:06 PM. Reason: Prices
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  8. #21
    Join Date
    Aug 2013
    Posts
    61
    Thanks, I'll check into this.

    The misting/steam humidifiers sound like good options. But are the steam ones prone to gross stuff growing in the water, or does it automatically flush frequently? I looked into this years ago and was told that the steam ones were not very sanitary. Has that been fixed?

    Also, I looked into the mist ones years ago too and was told that these made the ductwork rust pretty badly. Is this still a problem (or was it ever)?

    Do you have any recommendations as to brands? I spoke today with the HVAC contractor who will be doing this project (Carrier) and he is basically leaving this part up to me.

  9. #22
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,455
    Quote Originally Posted by ndeverest View Post
    Thanks, I'll check into this.

    The misting/steam humidifiers sound like good options. But are the steam ones prone to gross stuff growing in the water, or does it automatically flush frequently? I looked into this years ago and was told that the steam ones were not very sanitary. Has that been fixed?

    Also, I looked into the mist ones years ago too and was told that these made the ductwork rust pretty badly. Is this still a problem (or was it ever)?

    Do you have any recommendations as to brands? I spoke today with the HVAC contractor who will be doing this project (Carrier) and he is basically leaving this part up to me.
    Misting humidifiers require distilled water to avoid the silicates in the water from becoming air borne.
    Things growing in pad humidifiers are because a lack of overflow to flush the pad. Steam are expensive to operate and maintaince problems.
    So pad with overflow and several hours of dry time each day are my choice.
    Regards TB
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  10. #23
    Join Date
    Nov 2006
    Location
    Athens, Ohio
    Posts
    1,817
    Quote Originally Posted by energy_rater_La View Post


    when the bonnet sensor -name may vary by manufactor but called a bonnet senor cause its located near the top of exchanger, reaches about 165 degrees this sensor tells the fan to come on.
    thus warm air arrives in home.
    t-stat is satisfied and gas valve closes. the heat exchanger cools to 125 and sensor turns off blower.

    this bonnet sensor temps can be lowered manually or if fixed by manufactor your dealer can order this sensor to turn on at 145 and off at 110
    air at 110 may feel cool cause its fan assisted.
    Most furnaces no longer use a bonnet sensor. A pc control board is now used to control blower operation which is based on a timer rather than furnace temperature. It is possible to change the timer settings with DIP switches on the control board.

  11. #24
    Join Date
    Aug 2013
    Posts
    61
    Quote Originally Posted by teddy bear View Post
    Misting humidifiers require distilled water to avoid the silicates in the water from becoming air borne.
    Things growing in pad humidifiers are because a lack of overflow to flush the pad. Steam are expensive to operate and maintaince problems.
    So pad with overflow and several hours of dry time each day are my choice.
    Regards TB
    I've tried pad with overflow and it just didn't work for us, even with flushing it well and keeping it dry several hours a day. The pad itself just smelled bad, and made the air smell bad. We just don't want to attempt this again, even though theoretically this should work if done right.

    So I have three questions (and I know pad with overflow is your preference but please assume for the sake of this question that we are not including this an option):

    1) Since misting ones required distilled water, that would be a downside to them. But if we went through the hassle of getting distilled water available, do they work well? Do they achieve their goal, and are they not too much of a maintenance hassle? Do they cause rust problems?

    2) Do steam ones have the problem of stuff growing in them or has that been resolved?

    3) Ignoring cost, and assuming that pad with overflow is out, which do you prefer, steam or mist, and why?

    Cost is not my major focus. Lack of hassle, actually achieving good humidification, and not introducing other problems (rust, bacterial growth etc) are my main criteria.

    Thanks!

  12. #25
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,125
    Most, if not all modern steam humidifiers now have a purge cycle that dumps teh water every X hours. Prevents mineral build up. And helps prevent mold growth.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  13. #26
    Join Date
    May 2004
    Location
    south louisiana
    Posts
    3,189
    carrier's steam humidifiers are an intergal part of their homecomfort services.
    http://www.carrier.com/homecomfort/e...y/humidifiers/
    The cure of the part should not be attempted without the cure of the whole. ~Plato

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