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  1. #1

    Dehumidifer DR90

    I got the dehumidifier installed with the fresh air intake according to Ex: B on page 5 in this link. http://www.forwardthinking.honeywell...ll/69_2407.pdf

    Problem is I think my HVAC guy installed the damper on the Return side instead of on the Supply side. Can anyone explain what kind of negative effects this might have to my system?

    I have another question in regards to the duct itself. It is a metal duct system which were supposed to have been sealed with mastic and tape but I can feel with my hand a small amount of air leaking in almost every bend and connection. I wondered if it's common practice for it to have small leaks like that and also if the seam in the duct trunk line should be sealed with mastic and tape as well?

    Thanks in advance for any help with these questions.

  2. #2
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    Quote Originally Posted by momoformula70 View Post
    I got the dehumidifier installed with the fresh air intake according to Ex: B on page 5 in this link. http://www.forwardthinking.honeywell...ll/69_2407.pdf

    Problem is I think my HVAC guy installed the damper on the Return side instead of on the Supply side. Can anyone explain what kind of negative effects this might have to my system?

    I have another question in regards to the duct itself. It is a metal duct system which were supposed to have been sealed with mastic and tape but I can feel with my hand a small amount of air leaking in almost every bend and connection. I wondered if it's common practice for it to have small leaks like that and also if the seam in the duct trunk line should be sealed with mastic and tape as well?

    Thanks in advance for any help with these questions.
    Where is the unit located? If in a basement, a small amount of leakage is acceptable. In an attic, I would seal everything possible. A damper in the fresh air duct to the dehumidifier is suggested to vary the amount fresh air being introduced. In rare cases, a balancing damper can also be used in the return duct from the home to get more fresh air into the home. No other dampers should be used.
    Glad to see that you accept the merits of supplemental dehumidification and fresh air.
    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"

  3. #3
    Teddy Bear,
    yes I took the advice to use a dehumidifer with fresh air intake to make my house more comfortable to live in. Before I had no fresh air intake and VOC's would have a very strong smell and the air would get very stale. Big improvement with this system but the energy bill also went up in the middle of summer..

    The system is located in the attic of a spray-foamed house. (completely sealed)
    I do use a EARD 6 motorized damper on the fresh air intake before the dehumidifer. It's controlled by this thermostat: http://www.alpinehomeair.com/viewpro...ctID=453058719
    I don't know how that thermostat is regulating the cfm in my setup either. Since the damper just goes from fully closed to fully opened!?

    The damper I am talking about is this one http://shopping.yahoo.com/721987814-...r/user-reviews
    which is supposed to be installed on the supply side according to the Honeywell manual Ex B Page 5. I just wanted to know why they recommend that and since I don't have it if that would make my AC force cold/hot air back into the dehumidifer when heatpump is operating and dehumidifer is not!?
    Would the heatpump waste heated or cooled air and work harder because I don't have the damper there?

    Sorry for all the questions.

  4. #4
    Join Date
    Jun 2003
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    The small amount of air that is forced back through the dehu will go back to the home. Heated or cooled, no problem.
    Hopefully, the thermostat has the logic to open the fresh air damper and operate the fan on the dehu to bring in a portion of fresh air, mix it with house air, and blow the filtered mixture into the supply duct of the a/c for distribution through out the home.
    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"

  5. #5
    TB,
    I wanted to share my whole experience with this new house build.
    1. I got the HVAC system and foam installation engineered by Energywise Structures for my 1800sq/ft house. They provided recommended installer to do caulking/air-sealing and spray foam to their specs.
    2. I had a HVAC contractor install a metal duct system to their specs.
    3. I had exhaust only fans in 2 bathrooms and in kitchen installed. All fans sized to the room size according to their specs.

    This was all that needed to be done according to Energywise Structures for the house to have low energy bills and a healthy indoor air quality.

    I quickly found out that something wasn't right after I moved in. Smells from construction materials in the house was off gassing and the exhaust only fans wasn't doing enough to get rid of the smells. So in the fall I started opening windows and turning on exhaust fans to improve the indoor air. That helped but this was not a very practical way to get fresh air into the house.
    I decided to try an air cleaner/purifier. Bought this one http://www.iqair.com/home-air-purifi...gcmultigas.php
    Let me tell you that it wasn't the solution. That purifier got saturated with smells from off-gassing materials quickly and new filters aren't cheap! (Neither was the Air purifier…Wasted money in my opinion.
    At this point I also started noticing that I felt drowsy, got headaches and was low on energy. So I purchased a Co2 meter to verify Co2 levels. And as I had suspected they were pretty high.

    So I contacted Energywise again.. They told me to install a fresh air intake and a damper connected to a Co2 meter to open only when Co2 levels was high. A Demand Controlled Ventilation system, I thought about it and read as much as I could here on this forum about other options.. I thought since measuring only Co2 and opening fresh air when the levels are high isn't enough to reduce any off-gassing which goes on 24/7.
    So then I decided to install a dehumidifer with a fresh air intake, a Honeywell DR90. Got the HVAC contractor to install it. ( I had to rewire the thermostat, motorized damper and dehumidifer because the HVAC guys apparently didn't know how to wire it correctly to make it work :-/! they tried telling me I needed another controller...Oh well). So now I had a fresh air intake and dehumidifer installed between return and supply plenum of my air handler/duct system.
    It made a huge difference in indoor air quality but it also raised my power bill from last year when no fresh air was installed to this year with fresh air installed. This year between 8/19 to 9/19 my bill was $119 last year same time $90.75 . I guess this is the information that Energywise don't tell you on their website... The savings from using spray foam and their engineered drawings of duct and matched HVAC just got less when you figure that you need to buy a dehumidifer with fresh air intake to really make the house healthy to live in!?

    The fresh air intake is controlled by a Honeywell DG115EZIAQ thermostat that works according to ASHRAE 62 standard. Settings on Thermostat for ventilation are 1800sq/ft house, 90cfm, 3 bedrooms and 50%RH. And I keep the house temp between 70-72 degrees.

    I still monitor Co2 levels and have found that when I get home from work the levels are around 450-480ppm and when I leave in the morning they are around 770ppm. When I have my girlfriend over I have noticed that the ventilation don’t seem to be enough, (that’s two people and 3 dogs in a 1800sq/ft house) The Co2 levels in the bedroom are reaching 1100-1300ppm when we wake up in the morning which is too high.
    This leads me to think this:
    1. It is not enough of air coming in through the fresh air intake!?
    2. The air that comes in isn’t being distributed evenly through my duct system to all rooms because the dehumidifiers fan is not strong enough to push it through.
    3. There needs to be an exhaust fan working simultaneously with the fresh air intake to balance/improve the fresh air intake flow!?

    Any suggestions?!

    Thanks!

  6. #6
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
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    Quote Originally Posted by momoformula70 View Post
    TB,
    I wanted to share my whole experience with
    I still monitor Co2 levels and have found that when I get home from work the levels are around 450-480ppm and when I leave in the morning they are around 770ppm. When I have my girlfriend over I have noticed that the ventilation don’t seem to be enough, (that’s two people and 3 dogs in a 1800sq/ft house) The Co2 levels in the bedroom are reaching 1100-1300ppm when we wake up in the morning which is too high.
    This leads me to think this:
    1. It is not enough of air coming in through the fresh air intake!?
    2. The air that comes in isn’t being distributed evenly through my duct system to all rooms because the dehumidifiers fan is not strong enough to push it through.
    3. There needs to be an exhaust fan working simultaneously with the fresh air intake to balance/improve the fresh air intake flow!?

    Any suggestions?!

    Thanks!
    It is not uncommon for the to see the levels that you are getting. Two occupants and several dogs will have the levels of CO2 you have while you have adequate fresh air ventilation to purge indoor pollutants and renew oxygen. You need an air change in 4-5 hours to purge indoor polluntants. The CO2 levels with one in the home should be about 700 PPM. Also consider the location of the CO2 meter inrelation to the occupant. The closer the meter is to the occupant, the higher the CO2 concentration reading. This is a mixing issue. I would not change anything yet.
    Regarding cost, your well insulated and sealed building is paying dividends. You are getting the amount of ventilation you want at a very reasonable cost.
    Look good so far. Keep us posted. Ventilating when occupied is also a way of reducing cost. If you love those dogs, ventilating 24/7 does not cost that much. 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. #7

    Hmm

    I have come to this realization.

    The fresh air intake on the dehumidifer is a 6" flex duct about 8' long with a motorized damper that opens when thermostat says to ventilate. I realize now that I have no clue as to the air/cfm being sucked in. This is not controlled by the motorized damper as it opens to full. and the fan in the dehumidifer pulls about 237cfm according to the specs. This air is pulled from both the fresh air intake and from return plenum of my HVAC to be mixed. I guess I need to get the installer out there to measure how much fresh air is being pulled in to be able to set the thermostat so it works according to ASHRAE 62.2. Now here is the other not so funny thing.
    The fan ONLY in the dehumidifer uses 182watts when running. When the dehumidifier and fan is working it uses 800watts. The dehumidifier does not run based on the humidity in the outside air being brought in, this means it doesn't dehumidify the incoming air at all. So in reality the fan in the dehumidifier works just like any other fan with the exception that it pulls air form outside of your house and mixes it with your conditioned air inside of your house! That makes the setup of a dehumidifier with fresh air intake a very expensive setup, to purchase, install and run!
    Lets see how much it cost:
    Dehumdifier $1350
    Motorized damper $90
    Thermostat $7
    Backdraft damper $80
    Installation + material $511
    Cost of running fan only 24/7 per month $16
    Cost of running dehumidifier (0.8KW x h time running) x 0.12 dollars per KW.

    Now if I only wanted to bring in fresh air into the house and mix it with the air inside just like the dehumidifer fan does.
    I could have purchased a Panasonic Whisperline fan 240cfm which uses 57Watts $157
    Split up the intake air, one 6" to outside and one collection 6-10" point inside.
    Cost of running this setup 24/7 per month $5.09

    Hmmm... Cost of running fan is cut to 1/3 of the cost compared to dehumidifier fan!

    And lets assume the installation cost of the fan is the same as the humidifier (although it would most likely be considerably less) + a motorized damper for $83
    So $511+157+83= $751 total installation + cost of inline fan.

    Dehumidifier + installation cost and accessories $2038

    If I had to do this all over today I would for sure just buy an inline fan or an ERV since an ERV actually pre-treats the incoming air (lowers humidity and temperature). I would say that an efficient ERV would cost as much or more than the dehumidifier. A running ERV uses between 90-200w depending on make and model that is far less than the dehumidifier at 800watts and the by product of the dehumidifer running is heat so that heat has to be cooled down by your AC. Excess humidity with ERV or just an inline fan would have to be handled by AC/Heat pump. So depending on how efficient the AC is that would add to the cost of operating.. :/

  8. #8
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    Madison, WI/Cape Coral, FL
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    Quote Originally Posted by momoformula70 View Post
    I have come to this realization.

    The fresh air intake on the dehumidifer is a 6" flex duct about 8' long with a motorized damper that opens when thermostat says to ventilate. I realize now that I have no clue as to the air/cfm being sucked in. This is not controlled by the motorized damper as it opens to full. and the fan in the dehumidifer pulls about 237cfm according to the specs. This air is pulled from both the fresh air intake and from return plenum of my HVAC to be mixed. I guess I need to get the installer out there to measure how much fresh air is being pulled in to be able to set the thermostat so it works according to ASHRAE 62.2. Now here is the other not so funny thing.
    The fan ONLY in the dehumidifer uses 182watts when running. When the dehumidifier and fan is working it uses 800watts. The dehumidifier does not run based on the humidity in the outside air being brought in, this means it doesn't dehumidify the incoming air at all. So in reality the fan in the dehumidifier works just like any other fan with the exception that it pulls air form outside of your house and mixes it with your conditioned air inside of your house! That makes the setup of a dehumidifier with fresh air intake a very expensive setup, to purchase, install and run!
    Lets see how much it cost:

    If I had to do this all over today I would for sure just buy an inline fan or an ERV since an ERV actually pre-treats the incoming air (lowers humidity and temperature). I would say that an efficient ERV would cost as much or more than the dehumidifier. A running ERV uses between 90-200w depending on make and model that is far less than the dehumidifier at 800watts and the by product of the dehumidifer running is heat so that heat has to be cooled down by your AC. Excess humidity with ERV or just an inline fan would have to be handled by AC/Heat pump. So depending on how efficient the AC is that would add to the cost of operating.. :/
    How are you measuring the watts. The dehu and fan use less than 700 watts and should seldom operate 24/7. The fan usew 120-140 watts depending on pressures. The higher the air pressure the less the power.
    During the heavy cooling season, the a/c should be controlling your indoor %RH.
    Using only an ERV will saturate your home with the outdoor dew point air. You need real dehumidification to maintatin <50%%H during low/no cooling loads and +55^F outdoor dew points.
    Judging on your low indoor CO2 levels, probably over ventilating or the windows are open.
    I have tried to ventilate with only an ERV. The ERVs only transfer <50% of the moisture difference of the encoming moisture providing you are exhausting <50%RH. Without a dehumidifier, after an air change and the moisture from the occupants, you will be exhausting elavated moisture levels. The ERV will transfer much less moisture on the next air change. After a day of ventilation, the ERV will not be transfering any moisture. The exhaust moisture level will equal the incoming moisture level.
    I was a HRV/ERV man before becoming a dehumidifier man.

    Controlled ventilation with a good dehumidifier is more practical. Ventilate to point were you have 700-800 ppm CO2 when the home is occupied. Beyond that you are going for excellent air quality verses good air quality. If you are getting 700-800 ppm CO2 without any ventilation during cold weather, you do not need any additional fresh air.
    keep us posted your results. Do not forget to calculate your power factor when extimating KWH from amps.
    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"

  9. #9
    The watts are measured with the Dehumidifiers power chord connected to a watt-meter I bought at Lowes. Tested with fan only running and damper open 182W usage when adding dehumidifier 800w usage. I will make sure I take a reading when everything is not working to make sure the meter reads close to 0. I will give you an answer on this later today.

    The dehumidifier does not operate 24/7 for sure and neither does the fan. I used those numbers for comparison if you did want to ventilate 24/7 per your recommendations below when dogs are in the house.
    I still don't know how much air is being brought in via the fresh air intake so I don't know how to set the thermostat properly. I may have been over ventilating like you said. How many minutes per hour do you normally run your ventilation on your dehumidifer?
    I need to measure the cfm of the air being brought in via the dehumidifer to know 100% I guess.
    The problem however is not only ventilating based on CO2 it is also venting to rid the house of VOC/smells. I still have a smell in my attic (which is a non-vented attic) which leads me to believe that the spray-foam or other building products is off-gassing!?
    I might try to put an exhaust fan in the attic to see what that does and run for a few days.

  10. #10
    The damper and thermostat seems to be pulling around 18W
    I will get this watt meter replaced as I just found out it's not reliable for any items pulling less than 120W. :-(

  11. #11
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    Quote Originally Posted by momoformula70 View Post
    The watts are measured with the Dehumidifiers power chord connected
    The dehumidifier does not operate 24/7 for sure and neither does the fan. I used those numbers for comparison if you did want to ventilate 24/7 per your recommendations below when dogs are in the house.
    I still don't know how much air is being brought in via the fresh air intake so I don't know how to set the thermostat properly. I may have been over ventilating like you said. How many minutes per hour do you normally run your ventilation on your dehumidifer?
    I need to measure the cfm of the air being brought in via the dehumidifer to know 100% I guess.
    The problem however is not only ventilating based on CO2 it is also venting to rid the house of VOC/smells. I still have a smell in my attic (which is a non-vented attic) which leads me to believe that the spray-foam or other building products is off-gassing!?
    I might try to put an exhaust fan in the attic to see what that does and run for a few days.
    In a new house, 24/7 is good until you can not detect odors. The CO2 levels are the most accurate method of measuring the effective fresh air. I control my fresh air by CO2 levels. On windy, cold days, my fresh air ventilation is reduced to almost nothing. During calm warm weather, the ventilation matches the occupancy. I doubt that you are getting more than 70-80 cfm of fresh air unless you are significant negative pressure on the fresh air duct. Three occupants plus dogs suggest 800-900 ppm CO2 levels for good fresh air change. This is after several hours of occupancy and good mixing.

    You want enough fresh air to purge the indoor pollutants which an air change in 4-5 hours when the home is occupied. As the outside dew point declines, the indoor moisture levels also are good indicators of the amount fresh air you are getting. The difference between the inside/outside dew points is determined by the amount of moisture from the occupants and the amount of fresh air moving through the home.
    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"

  12. #12
    This is interesting.
    Just for the record where is your house located?
    On slab or crawlspace foundation?
    How is it insulated?
    Was everything caulked to seal it up from base-plate to between all studs?
    How big is your house?
    Conditioned or unconditioned attic?
    Backdraft dampers on all exhaust fans? Including range hood? And what kind of damper do you use!? one that is better than what comes with most fans or just the stock backdraft dampers?! (On this note I found out yesterday that my range hood vent does not have any back draft damper installed at all. It is a 6" metal duct vented to the outside.) So when I run my bathroom fans the 6" duct is acting like a passive inlet for air. I will get a back draft damper installed for sure!!

    In the summer down here in Mobile AL the smell in my attic and house is stronger. Which seems to indicate that the foam is off-gassing more in a humid hot climate or it is like you said, that the house is getting more 'natural uncontrolled ventilation on colder dryer days'.

    This is starting to drive me nuts! I don't want to live in a house with unhealthy indoor air quality because of off gassing from foam insulation or other building materials.. I wonder were one can get proper testing of the air done without it costing an arm and a leg!?

  13. #13
    Fan uses 150W (tested with kill a watt EZ). Seems to be accurate... tested measuring CFL light at 12W and hairdryer at 1875W.

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