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  1. #40
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    Air can infiltrate from the outside to the inside through any number of sources. In your case, I'll bet there are multiple sources.

    For example, depending on the structure, wall switches and outlets can be a common source. Vents such as in a dryer, water heater, or kitchen and bath exhausts are big holes to the outside. Cooking creates moisture. People create moisture by just breathing. Then there are things like showering. It goes on and on.

    Before you spend any time or money, take a step back and think about what the problem really is, what results you are trying to achieve, and the possible methods to reach that goal.


    Quote Originally Posted by utkara View Post
    Hi,

    Just an update - I am noticing that with all the windows being shut, with an increase in the outside humidity, the indoor RH levels have already increased - currently at 61%, 64% and 66% in the different rooms with temps ranging between 74.66`F to 77.54`F. (no air con running in any rooms)

    Is that be a clear indication that there is air infiltrations through the windows? If so, I have contacted someone to come and replace/repair the rubber gaskets. How can I ensure / check that post replacing the infiltrations have been taken care off?

    Thanks once again for the help.

    Regards..

  2. Likes utkara liked this post
  3. #41
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    Dec 2015
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    Quote Originally Posted by BBeerme View Post
    Air can infiltrate from the outside to the inside through any number of sources. In your case, I'll bet there are multiple sources.

    For example, depending on the structure, wall switches and outlets can be a common source. Vents such as in a dryer, water heater, or kitchen and bath exhausts are big holes to the outside. Cooking creates moisture. People create moisture by just breathing. Then there are things like showering. It goes on and on.

    Before you spend any time or money, take a step back and think about what the problem really is, what results you are trying to achieve, and the possible methods to reach that goal.
    Thanks for the response...

    How does one identify the various sources of air infiltration? How do I know if there are in wall switches / sockets?

    I agree that source of moisture could be quite a few - as you mentioned - therefore one can try and limit those activities which create excess moisture.

    To be honest, I just want to maintain the RH / moisture levels at an acceptable level in the apartment in order to avoid a relapse of mold/mildew. Although I have bought a standalone dehumidifier, I am hoping to identify the root cause of the high RH (which appears to be linked with outside humidity) plus the aircon does not seem to be dehumidifying the air when operating, instead increases RH levels. So want to know how I can have this resolved as the guys out here do not seem to have a clue on what to do - lacking quality HVAC technicians in Dubai.

  4. #42
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    Dec 2015
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    Quote Originally Posted by utkara View Post
    Hi HVAC Members,

    Need your help - being in a similar situation like curious_owner, have decided to use this thread instead of creating a new one. Live in an apartment where the air conditioning is through central cooling (chilled water).

    An upfront honest disclaimer that I am a newbie when it comes to HVAC / IAQ matters and started doing some reading very recently when I encountered increased indoor moisture/RH levels, which lead to a mold / mildew attack on clothing, leather goods, wood related items, shoes, etc. I have managed to clean out and/or dispose off the affected items and thus have not yet identified a re-lapse (been nearly two months).

    Sometime in end September / early to mid October (when the cooler weather started to begin - am living in the Middle East thus desert-ish weather), my wife and I started experiencing that our bedroom felt quite moist / wet (clothing, flooring, etc) - at that time, we were not sure why and continued our normal life - a couple weeks later we identified the mold/mildew (whiteish stuff of clothing/leather goods) which lead to contact a professional duct and HVAC cleaning and disinfection company, who told us that the aircon and its components would need to be cleaned as it was not dehumidifying the air, thus leading to the increased indoor moisture.

    We believed it and agreed to get it done and they took nearly a full day (three units in the apartment) to clean out the ducts, filters, coils, drip trays, etc. However, to no avail, when we ran the aircon, the indoor RH levels were not improving (hovering in the mid to late 60's). Post cleaning, one of the guys stated that the lining in one of the unit's supply ducts was broken and should be replaced, which could also be a source of moisture (is that true?)

    As the weather started to improve, our usage for aircon decreased, however I did not see that the indoor RH levels were any better without the aircon running (which I was assuming was increasing the indoor RH as it was not dehumidifying the air). We contacted another company to conduct an inspection to help identify what would be the rootcause / source of moisture and they concluded the following;

    (a) The aircon was not operating appropriately as they measured the air supply from two different units and found the readings to be (i) 61.88`F and 87%RH and (ii) 67.28`F and 78.6%RH. When the aircon were turned on, they were instead increasing the indoor RH levels instead of decreasing.

    (b) Air infiltration occurring through the windows and door - they found traces of dust / sand in the window seals and found a gap underneath the main door which was resulting in humidity from the corridor to come in (have taken care of that by installing a doorstrip)

    (c) There is a fresh air supply duct coming into the master washroom, in which the air was measured to be 75.38`F and 65.4% RH (this was previously closed but didnt have any such impact on RH and currently is set at 50% opening).

    In my attempt to find an HVAC expert who could help inspect the air con and find out the issue [as recommended in (i)], to be honest, I have not been quite successful but came across one, who visited a few days back and tested one FCU. Before running it, the indoor RH in that room was exactly at 60% and after running it for about 30-40 mins, the RH started increasing and went up somewhere bw 66-68% (supply vent was showing similar readings as mentioned in point (a) (i) above (also this was not the duct which was found to have a broken lining). So their conclusion was that they would need to service all of the air con units and their components (filters, coils, etc) using some chemical and would also need to descale the chilled water pipes.

    So in vain, I ask you experts out here, who are pretty learned in this field;

    (a) Is this diagnosis even correct i.e. servicing of all the parts which would result in the aircon dehumidifying the air? If so, I had previously gotten the HVAC cleaned, what would that have been? (tbh I dont know what exactly they did but they were the most reputable and highly recommended company for duct and hvac cleaning)

    (b) My current indoor temp and RH levels are at follows in the different rooms (i) 74.84`F and 52%RH, (ii) 75.2`F and 48%RH and (iii) 75.38`F and 50%RH - No air con is running since 24 hrs and in rooms (ii) and (iii) the windows are open while in (i) I have a pedestal fan running - thus should such RH levels worry me that there is another source of moisture in the apartment (accuweather is showing humidity to vary between 20% to 30% - I havent taken the hygrometer outside to measure the RH levels in my vicinity)

    (c) Should I contact my building maintenance guys who manage the central air con system and if so, what should I ask them to check or look for?

    I'm sorry if I may not have provided all the relevant information as I am very new to all this and would appreciate all the guidance that you guys can provide me so I can execute that.

    thanks in advance
    Anyone ????

  5. #43
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    Quote Originally Posted by utkara View Post
    Anyone ????
    Someone with the expertise in this area of hvac, will be along sometime. It is beyond my field of scope. Most of them are probably out in the field working.

    Sent from my Note3, using, Crapatalk
    "If you can’t describe what you are doing as a process, you don’t know what you are doing." ~ W. Edwards Deming

    All those who wander..are not lost.

    Do NOT..mistake my kindness for weakness.

    The early bird may get the worm..but the second mouse gets the cheese.

  6. #44
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    If you have enough of a temp difference between indoors and outdoors, then an infrared camera can often show you were the air leaks to your building envelope are.

    Might be able to rent one or find someone who has one.


    Quote Originally Posted by utkara View Post
    Thanks for the response...

    How does one identify the various sources of air infiltration? How do I know if there are in wall switches / sockets?

    I agree that source of moisture could be quite a few - as you mentioned - therefore one can try and limit those activities which create excess moisture.

    To be honest, I just want to maintain the RH / moisture levels at an acceptable level in the apartment in order to avoid a relapse of mold/mildew. Although I have bought a standalone dehumidifier, I am hoping to identify the root cause of the high RH (which appears to be linked with outside humidity) plus the aircon does not seem to be dehumidifying the air when operating, instead increases RH levels. So want to know how I can have this resolved as the guys out here do not seem to have a clue on what to do - lacking quality HVAC technicians in Dubai.

  7. #45
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    Quote Originally Posted by BBeerme View Post
    If you have enough of a temp difference between indoors and outdoors, then an infrared camera can often show you were the air leaks to your building envelope are.

    Might be able to rent one or find someone who has one.
    Thanks - did try that approach - didnt help due to not much temp differences.

  8. #46
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    Where to start??
    50-55%RH will control mold and dust mites. At 75^F, 50%RH is a 55^F dew point. Your cooling coil must be <45^F and the fan moving the air through the cooling coil must be slow enough to be have a <50^F dew point.
    Chiller temps are usually to high and air flow to much to get adequate dehumidification.
    When you calculate the dew point of the supply, it must be less than 50^F to reduce the dew point of the air in space to <55^F.
    Get that startened out as much as possible. Next a 70 pint dehumidifier in the space is the last resort. The dehumidifier is needed during times of low/no cooling loads and high outdoor dew point. If your cooling is too war and/or air flow to high, the dehumidifier may have to operate all the time.
    Keep us posted and give us the 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"

  9. #47
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    Quote Originally Posted by teddy bear View Post
    Where to start??
    50-55%RH will control mold and dust mites. At 75^F, 50%RH is a 55^F dew point. Your cooling coil must be <45^F and the fan moving the air through the cooling coil must be slow enough to be have a <50^F dew point.
    Chiller temps are usually to high and air flow to much to get adequate dehumidification.
    When you calculate the dew point of the supply, it must be less than 50^F to reduce the dew point of the air in space to <55^F.
    Get that startened out as much as possible. Next a 70 pint dehumidifier in the space is the last resort. The dehumidifier is needed during times of low/no cooling loads and high outdoor dew point. If your cooling is too war and/or air flow to high, the dehumidifier may have to operate all the time.
    Keep us posted and give us the issues.
    Regards TB
    Thanks TB for the response - was hoping you would respond back, after reading your posts earlier .

    I will call for a specialist to measure the cooling cool temps but pardon my ignorance (and unfortunately the technicians down here appear to be more cluless at times and have previously told me that nothing can be done), how should they be measuring the cooling cool temps (infrared temp readers?) and in the event that the temps are not what you have suggested , what should they be looking to do? Reason I ask is because the last set of technicians who came were so confident that once they service the unit using some chemicals, they issue would be resolved ( which I personally was not too convinced with)

    I have two standalone dehumidifiers which I do use when RH levels go in the 60s range - with the weather lately I haven't had the need to use them as temps outside are low so don't need the aircon running .

    Thanks for the help

  10. #48
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    Quote Originally Posted by utkara View Post
    Thanks TB for the response - was hoping you would respond back, after reading your posts earlier .

    I will call for a specialist to measure the cooling cool temps but pardon my ignorance (and unfortunately the technicians down here appear to be more cluless at times and have previously told me that nothing can be done), how should they be measuring the cooling cool temps (infrared temp readers?) and in the event that the temps are not what you have suggested , what should they be looking to do? Reason I ask is because the last set of technicians who came were so confident that once they service the unit using some chemicals, they issue would be resolved ( which I personally was not too convinced with)

    I have two standalone dehumidifiers which I do use when RH levels go in the 60s range - with the weather lately I haven't had the need to use them as temps outside are low so don't need the aircon running .

    Thanks for the help
    It sounds like you doning what you can.
    Slowing the air flow through the cooling coil may help. A better air filter or added restriction like paper towel will do while measuring the air supply to the space. You will have understand how to determine the dew point of the supply air. Go for the lowest dew point and yet be able to cool the space. Fan must be off or auto mode when not cooling to avoid re-evaporation of moisture from the coil back to the space when not cooling.
    Keep us posted.
    Regards Teddy Bear
    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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