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  1. #1
    Join Date
    Dec 2009
    Location
    Toronto, Ontario
    Posts
    19

    Question Condo A/C High Humidity

    Hi HVAC Experts:

    I've just moved into a four year old condo. My unit is about 1,000 sq.ft. (2 bedroom plus den and two baths). It is a corner unit (west and north-west exposure) with windows along the entire west side and north.

    The condo has two wall units (Livingroom and Den) with the intake at the base of the unit, then the thermostat, then the cold/heat vent at the top of the wall. Vents are located in the spare room on the back the Living Room main wall unit and same for the Master Bedroom from the Den.

    The thermostat is not working properly because it is right below the vent, e.g. in order to maintain a temperature of 72-73 F I need to place the thermostat at 65-66 F.

    The other problem is high humidity levels. I've tried just about every solution I know and they are not working or can't keep up with such high humidity levels. The unit is always 'clamy' and 'damp'. The humidity levels range from 60% to 70%.

    I purchased a dehumidifier and its been running full tilt for four days and I was able to reduce the humidity levels down to 60%. Unfortunately, it goes back up! The source appears to be the a/c.

    I don't know the type of system that is on the rooftop of our condo. I will find out from Management.

    Our building is about 16 stories high and just under 200 units. What would be causing the a/c not too work ... a big de-humidifier.

    I need to address the problem with our Property Manager but would love some suggestions as to what to look for and what could be the problem(s).

    Thanks bunches, SK

  2. #2
    Join Date
    Jun 2010
    Location
    northwest connecticut
    Posts
    58
    16 stories i would have to assume you have a central chilled water plant in the building. So there also may be some type of ventilation air introduced also, wich could affect humidity lvels if not properly regulated. If the ac runs for long periods of time you will be able to acheive lower humidity levels, assuming everything is functioning properly. If it runs for very short periods of time that could be an issue for humidity control. good luck

  3. #3
    Join Date
    Dec 2009
    Location
    Toronto, Ontario
    Posts
    19

    Question High Humidity Levels

    Hi HVAC1966:

    Thanks so much for getting back to me. I've tried lowering my thermostat but it seems to produce more humidity. And then it becomes cold and clamy.

    I gather from your reply that it is the mixing of too much outside air which is causing the higher humidity levels.

    Thanks, SK

  4. #4
    Join Date
    Jun 2010
    Location
    northwest connecticut
    Posts
    58
    could be, and if it is that simple if you wher to have somebody proffesional look at it , would most likely be a simple fix

  5. #5
    Join Date
    Dec 2009
    Location
    Toronto, Ontario
    Posts
    19

    Confused Condo Humidity Levels

    Hi hvac1966:

    I still have no concrete answers as yet.

    The HVAC guy that's in charge of the chillers is hired my the management company that runs the building. Wouldn't say what water temperature he's using in the chiller. I suspect that our management is trying to save money.

    I had the technician in to check the fan coil units and the values are open. Filter is clean, etc. However, I did notice that the pan is dry considering we have so much moisture/humidity.

    I'm at the end of the hall in a corner unit. May be the design is poor. The fresh air coming in around my door has high humidity levels. If the a/c is work properly in the building, the hallway shouldn't be that humid (66% or higher).

    I cannot lower the thermostat below 67F. If I do, the humidity levels in the unit go way up (70%). If I keep it at that temperature and have the dehumidifier running full throttle, I can usually keep the humidity levels to between 55-60 percent. I have empty the unit six times a day. If it stops for 20 minutes or so. It will be up about 3%.

    I have engineering hardwood, antiques, and very bad arthritis. Humidity is detrimental to all of them.

    Any more suggestions, StormKloud

  6. #6
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,266
    How big is your dehu and how much water is removed per day? Slow the amount of air flowing over your chilled water coil. Better filter or slowing fan. Measure in/out temps of the air. Fan setting "Auto" mode.
    Condos do not have enough cooling load to remove the moisture from occupants and natural infiltration. Bath/kitchen exhaust should be limited to bath/kitchen use. Some condos have constant exhuaust. Could be more than you need to purge pollutants. This can be check by monitoring the CO2 levels when you are in your condo.
    Keep us posted, we fix this problem all the time.
    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
    Join Date
    Dec 2005
    Posts
    1,908
    You must find the source of the humidity entering your unit/condo. Unfortunately, no one here can help since they are not there to investigate your condo.

    From what you said, It is NOT the a/c unit does not remove enough moisture. But the moisture is introduced into you condo. Find it by doing this simple test.

    Run your a/c unit and close all doors and windows for 20 - 30 minutes. Walk to your front door and BARELY crack it open. Use a lighter and put it at the door's crack.

    If the flame moves in, you have air leaks at the supplying duct somewhere.

    If the flame moves out, your unit takes in too much fresh air. It means you may have cracks in the return box somewhere.

    Good luck

  8. #8
    Join Date
    Jan 2008
    Location
    Ottawa, Canada
    Posts
    166
    From my experience working in these type of condos in my area, you have chilled water fan coils in your space with no fresh air. Where I find the humidity problems arise is in the hallways. In many designs in my area 100% fresh air is supplied to the hallways, and more often than not this is unconditioned air, in the summer anyways. Therefore high humidity levels in the hallway, this high humidity condition WILL make it's way into you space from cracks around the door etc...
    Just my 2 cents, not saying that this is your situation, but a possibility none the less.

  9. #9
    Join Date
    Feb 2005
    Location
    In a van by the river
    Posts
    618
    At 72 degrees with 60% RH your dew point would be approximately 60.5 degrees. Don't know what the chilled water temp is at the coil, but it should definately be below that and condensation should be visible. You're saying the pan is dry. Is the existing system capable of dropping temperature? Does it seem like it cools good, too good or not so much?
    ## + years in the field never made you a know-it-all This industry is far more diverse than you are

  10. #10
    Join Date
    Dec 2009
    Location
    Toronto, Ontario
    Posts
    19

    Confused Condo

    Hi Teddy Bear, just-opinion, CDNTech and git-r-dun:

    I'm emptying the humidifier about 6 times a day (35 pints). I have the thermostats set at 67-68 F. Fan is on auto and low (1). The condo temperature is usually at 74 F. In the three weeks since we moved in, I haven't seen it go below that temperature.

    Temperatures outside were close to 90 F and very high humidity of 80 percent or more a week ago. The unit was very hot and humid. The heat wave finally broke. Saturday we've had very little sun, cloudy and rain. Temperatures outside are about 68 to 71 F and with moist air. My humidity levels with everything closed were about 61-65% on Saturday and Sunday.

    Today, was cool and windy and moisture levels have dropped. Therefore, my humidity inside the condo has finally dropped to 52%. The humidifier runs continuously. We also haven't been cooking that much either because we just moved in.

    This week our weather will be sunny with temperature will range from 72-80F. I will keep a record all week.

    The two bathrooms: Main bathroom vents at about 45 and the Master Bedroom is farther away at about 17. Both are standard condo exhausts and share one fan between them. I hope to change that soon.

    I used my digital thermometer and the temperature from the vents at the top of the fan coils is about 65F and humidity levels are 66%. This is the part that I don't understand. The fan coil doesn't remove moisture. If anything it creates more. If I leave my humidifier off for say about one hour. Levels in here would rise by about 5% or greater.

    We are at the end of hall in a corner unit. [It is a corner unit facing west and north west. The majority of windows are facing west and two are on the north side. ] Fresh air is brought into the condo via the hallways as mentioned by CDNTech. It feels like it is air conditioned because it is cool and clammy. The moisture levels in the hallway are very high. They average about 70%. The cracks around my door are there to receive this fresh air.

    This appears to be one of my major sources of humidity. The others would be cooking, cleaning, bathrooms, showers, washer/dryer, etc. Since we've been here such a short time we haven't done too much cooking, etc. My humidity levels in here would be through the roof.

    Git-r-dun - the pan were bone dry!? I didn't see any visible signs of condensation inside the fan coil unit(s).

    I'm use to large home a/c units on a high efficiency furnace. Ours worked really well in our house and the humidity levels were terrific. Even in nasty hot and humid weather.

    Is there any way to fix this problem?

    Are my coils too small for 1,000 sq.ft. (I think they are set to a minimum standard of 1.5 tonnes). Do I need 2 tonnes of a/c.


    Thanks bunches, sk

  11. #11
    Join Date
    Feb 2005
    Location
    In a van by the river
    Posts
    618
    At 65 degrees from vents, there will be no dehumidification as you are not going below dew point. I'd find out what kind of water temperature they are supplying from the chiller. If it's in the forties, which it should, I'd check to see if your coils aren't air locked. Weather your unit is undersized or not would not necessarly be a concern just yet. Your vents should be blowing below 65 regardless.
    ## + years in the field never made you a know-it-all This industry is far more diverse than you are

  12. #12
    Join Date
    Dec 2009
    Location
    Toronto, Ontario
    Posts
    19

    Confused Condo Humidity Levels

    Hi git-r-dun:

    I have to start typing again because the system kicked me out!

    The stats are as follows:

    Today's weather is nice.
    Environment Canada: 14:00hrs * Sunny 22C * 68% Humidity * 16 ESE 15 Wind * 27 Humidex

    Water Temperature 48 F (measured at pipe)
    Return 70 F
    Supply 60 F
    Humidity in Room at Time of Measuring 55%
    Turned off dehumidifier
    Fan on low speed (1)
    Coil damp but no run-off
    15 degree D - low end of a/c range

    There is lots of air infiltration from door (hallway) and bath exhaust fans (damper non-existent). Hallway in condo is not air conditioned.

    It is an Enerzone VFC450 (120 V) which I can only assume means 4,500 BTUs. I have two units for 1,000 sq.ft. Therefore, 9,000 BTUs or 3/4 tonnes of a/c.

    With all the air from hallway and back drafts the a/c unit cannot keep up with moisture levels. Too much outside air??

    How to solve problem? Weather strip door if condo gives permission. Also replace bathroom fans with a proper damper (this one could be expensive since the wiring is not in place).

    What about re-sizing both units. Would that help?

    Any other suggestions.

    Thanks, sk
    Last edited by StormKloudk; 08-24-2010 at 08:58 PM. Reason: correction

  13. #13
    Join Date
    Jun 2003
    Location
    Madison, WI/Cape Coral, FL
    Posts
    6,266
    Quote Originally Posted by StormKloudk View Post
    Hi Teddy Bear, just-opinion, CDNTech and git-r-dun:

    I'm emptying the humidifier about 6 times a day (35 pints). I have the thermostats set at 67-68 F. Fan is on auto and low (1). The condo temperature is usually at 74 F. In the three weeks since we moved in, I haven't seen it go below that temperature.

    Temperatures outside were close to 90 F and very high humidity of 80 percent or more a week ago. The unit was very hot and humid. The heat wave finally broke. Saturday we've had very little sun, cloudy and rain. Temperatures outside are about 68 to 71 F and with moist air. My humidity levels with everything closed were about 61-65% on Saturday and Sunday.

    Today, was cool and windy and moisture levels have dropped. Therefore, my humidity inside the condo has finally dropped to 52%. The humidifier runs continuously. We also haven't been cooking that much either because we just moved in.

    This week our weather will be sunny with temperature will range from 72-80F. I will keep a record all week.

    The two bathrooms: Main bathroom vents at about 45 and the Master Bedroom is farther away at about 17. Both are standard condo exhausts and share one fan between them. I hope to change that soon.

    I used my digital thermometer and the temperature from the vents at the top of the fan coils is about 65F and humidity levels are 66%. This is the part that I don't understand. The fan coil doesn't remove moisture. If anything it creates more. If I leave my humidifier off for say about one hour. Levels in here would rise by about 5% or greater.

    We are at the end of hall in a corner unit. [It is a corner unit facing west and north west. The majority of windows are facing west and two are on the north side. ] Fresh air is brought into the condo via the hallways as mentioned by CDNTech. It feels like it is air conditioned because it is cool and clammy. The moisture levels in the hallway are very high. They average about 70%. The cracks around my door are there to receive this fresh air.

    Is there any way to fix this problem?

    Are my coils too small for 1,000 sq.ft. (I think they are set to a minimum standard of 1.5 tonnes). Do I need 2 tonnes of a/c.
    , sk

    I am attaching weather underground weather data for Toronto from Aug. 2010.
    You are up against some tough conditions. The summer winds are high and appear to from the northwest mostly. This means you may be getting the most fresh air on your side of the building. Also your temperatures/outdoor dew point are all over the place. Some are +70^F, like FL.
    The important point is that when outside dew points are above 55^F, fresh air entering your 75^F home raises the %RH above 50%RH. You add moisture from breathing and activities. Some estimate this to be 1lb. per hour per 2 occupants.
    When the outdoor dew point is <55^F, fresh air moving through your home reduces the %RH below 50%RH. This will be interesting this winter.
    Back to the green grass season problems. An estimate of how much fresh air enters your home by using the amount of moisture removed by the dehu. Using the moistue content of the outside air and the moisture content of the inside air along with amount of moisture removed. Also the hours of occupancy X the number of occupants would have to be estimated. An expample would be 35 lbs. of moisture removed by the dehu in 24 hours 1.5 lbs. of moisture per hour. You described inside on Sat. at 74^F, 63%RH--61^F dew point. Outside was 68-71^F 70%RH,--65^F dewpoint. If you were not in the home, I would estimate 180 cfm of infiltration as an average. It was windy last week.
    If the occupants contributed 15 lbs. of moisture for the day, the fresh air flow would be estimated at 100 cfm for the day based in your numbers.
    Here are your choices. 100 cfm of fresh air is a little high but on a calm warm day, expect the infiltration to drop to 50 cfm or less. 50 cfm is ideal for your size. Air tighting would help during windy weather. Get the chilled water temperature down to <42^F and keep your dehumidifier. If you can not get the water temperature lowered increase the size and efficiency of your dehumidifier. I suggest a Santa Fe Compact (High eff. 70 pt./d) connected to your a/c ducts and located near the a/c. This would maintain <50%RH during 65-70^F outdoor dew points.
    This is an interesting example of the effect of outside infiltrating air. Keeping your home at 35%RH during the coldest, windy weather will require 2lbs.per hour of humidification during your average winter weather. Your presents will supply some of the moisture but you will a humidifier.
    Homes with adequate fresh in the summer need a dehumidifier plus a properly setup a/c. If the a/c is not setup right and/or the home leaks, you need a larger dehumidifier. Homes with adequate fresh in the winter need some humidification. Homes excess air leakage need a larger humidifier.
    Regards TB
    Attached Images Attached Images
    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"

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