high humidity

[opti]

noticed a little mold/mildew around one of my vents, and tried to find a water leak. I couldn't find any, but while trying to diagnose it I noticed my humidity level in the house is pretty high - about 50-55%. I'm in Dallas, and the outside humidity is about 32% currently, but my inside humidity is about 55%. My system is 2Bryant 2.5 ton systems (zoned one per story), in a 2 story 2600 sq ft home. The house is about 5 years old. The humidity doesnt' really change much if I run the system for extended periods or just normally. I called a service company, they came out and did a check. They weren't real sure about the humidity, but they said that an issue I had was low air flow. They claimed for my 2.5 ton system I should be getting 1000cfm, they were only seeing 700. They said my 20x20 return with a 14" duct was too restrictive, and for $1000 they'll add another 2 10" returns to increase the airflow. They weren't real sure if this was my humidity issue or not, but felt that it would probably fix it. He said everything seemed fine across the coil, and that the CFM issue was the only real thing he could find. Of course, i'll get a 2nd opinion before committing to that kind of work on a fairly new system. Any ideas on my humidity problem? It's usually 34% or so at work with a pretty old system on 73 degrees. No matter what I set mine to I just can't get below 50%. I'm worried about mold issues, and why mine won't dehumidify in general. They lowered the blower speed from high to med-high to try and get it colder across the coil, but it didn't seem to help. I think he was saying because of the airflow issue he couldn't charge it as much as he thought it should be, but he was pretty deep into superheat technical talk and most of it was over my head. $215 later they still don't seem know why mine system won't dehumidify.

[hvacfella]

Hopefully they checked to see if condensate was blowing off of the surface of the cooling coil or not ; ive had this happen a few times in my travels . Your homes foundation might be laden with moisture creating high humidity within the home...especially after a heavy rainstorm. If you have a furnace mounted humidifier, make sure the solenoid valve isnt stuck letting water in the humidifier then into the airstream - had this happen just the other day on a job. Also, if you cook alot or take showers alot, you can expect your indoor humidity to be higher than normal. Another frequent cause of high humidity in a house, is a grossly oversized Cooling System which cools so fast that it doesnt run long enough to dehumidify properly. If all of the above have been looked at closely, then, obtaining a Portable Dehumdifier such as a Sears Brand 50 pint per day capacity unit...should help quite a bit.

[cem-bsee]

read lots here -- most common problem is oversized -- do you have crawl? does ground slope down 6" in 10ft away from house?

[opti]

Ground slope was adequate during the inspection ( I remember him going over that specifically). There's no crawl, it's a slab foundation (no basements here either). There hasn't been any rain in quite some time. I don't think there's a humidifier at the furnace. The system doesn't run all that hard, but it does run for good 30 -60 minute stretches. I tried putting it down to 67 just go get a good run time on it , and it didn't help at all. My humidity goes down a tad if I open all the windows and crank the exhaust fans. As for a dehumidifier, shouldn't the AC be doing that? 55% when it's 32% outside is pretty abnormal, isn't it? It's a pretty dry climate here. When I put the hygrometer up to the vent with the AC on, it starts climbing pretty quick .

[Edited by opti on 06-24-2005 at 10:45 PM]

[beenthere]

You have low air flow, so he slowed down the blower?

Need to have your duct checked for air leaks.

Sounds overs sized.

Set the down stars stat, about 6° warmer then the upstairs, and see if that makes a difference this weekend.

[hvacfella]

If your system is running for 60 minute stretches between normal cycles...i would highly suspect that the system is undercharged of refrigerant and/or that the entire system needs 'properly' servicing including : thorough cleaning of the Condensor Coils and Cooling Coils. Further, the Tech should make absolutely sure that the Cooling COil is sealed tight so no air bypasses around the Coil --- this is very typical of hack installations and of course does contribute to a large quantity of air not being conditioned . Id obtain a good Tech to come out .

[opti]

Originally posted by beenthere
You have low air flow, so he slowed down the blower?

Need to have your duct checked for air leaks.

He said he thought that might get it colder across the coil and help the dehumidification. He didn't have a way to check for leaks that I could tell, he did apply some duct sealant to an area that had some loose caulk in the return. He didn't know if it was leaking or not. He checked the refrigerant, but said he couldnt' add more because of the airflow issue, and superheat technobabble, and that it would liquidify, bleah. So basically it was "spend this 1000 bucks to fix your airflow problem"

anyone know of good ole cagey tech in the dallas area? I'm a little north in McKinney. this has been very frustrating. I see some of you guys talking about trying different size coils and bulb locations. That's the guy I want. The tech that came out was from a respected local company, but I think he was pretty new to the field. $215 later all I have is an estimate for $1000.

[Edited by opti on 06-25-2005 at 09:51 AM]

[opti]

Originally posted by beenthere
You have low air flow, so he slowed down the blower?

Need to have your duct checked for air leaks.

Sounds overs sized.

Set the down stars stat, about 6° warmer then the upstairs, and see if that makes a difference this weekend.

Questions, if it's oversized, is it just lack of run time that keeps it from dehumidifying? When I cranked it down to 67 to make it run a while it didn't help either. I'm trying your 6* test now. upstairs is 72, I'll put down on 78. How'd you get the little degree o up there by the way?

you guys have been very helpful! Thank you.

[craig1]

if the humidity is higher inside the house than outside, you have to find the source of humidity. as hvacfella said, showers and cooking could be the cause, but you could also have more serious problems like a plumbing leak or cracks in your foundation

[opti]

I've been running the exhaust fans lately. I didn't know you should run them really, until I started digging into this problem. My humidity today is about 54% inside, but it's 58% outside so I'm on the right side of the battle for a change. When I put my hygrometer up in a vent, it starts shooting up really fast. It'll top out to 99% in pretty short order. I'm really hoping this is just an HVAC problem, the foundation cracks and leaky plumbing don't sound very fun (or cheap) to troubleshoot. I've turned off my sprinkler system, and I'll leave that off for a while to see if that impacts the issue.

[beenthere]

The air coming out of the vents while the a/c is running will always be have a high RH.

Because the air temp is so close to the dew point.

Use alt 0176 for the ° symbol.

With low air flow, your coil temp is already lower, so slowing down the blower just makes the air flow too low, and risk freezing the coil, and flooding liquid back to the compressor.

If (and I said IF)your systems are over sized, you won't be able to get a handle on the humidity.

In that case your choices are , either properly sized a/c units, or a whole house dehumidifier.

If you have the time, you can click on the bulls eye above, and do youor own load calc, and find out if your systems are over sized.

[opti]

I'll run through that sizing in a bit. Thanks so much for the help. Would a properly sized system or a whole house de-humidifyer be the better bang for the buck? I saw the Ultra-Air 100v that looked like it would be a nifty solution, but I haven't seen pricing anywhere. Is the properly sized unit just a coil swap, or does the whole shibang have to be replaced?

[opti]

ran the sizing, but it just said 'trial version' on the reports over all the data other than what I input.

[teddy bear]

Originally posted by opti
noticed a little mold/mildew around one of my vents, and tried to find a water leak. I couldn't find any, but while trying to diagnose it I noticed my humidity level in the house is pretty high - about 50-55%. I'm in Dallas, and the outside humidity is about 32% currently, but my inside humidity is about 55%. My system is 2Bryant 2.5 ton systems (zoned one per story), in a 2 story 2600 sq ft home. The house is about 5 years old. The humidity doesnt' really change much if I run the system for extended periods or just normally. I called a service company, they came out and did a check. They weren't real sure about the humidity, but they said that an issue I had was low air flow. They claimed for my 2.5 ton system I should be getting 1000cfm, they were only seeing 700. They said my 20x20 return with a 14" duct was too restrictive, and for $1000 they'll add another 2 10" returns to increase the airflow. They weren't real sure if this was my humidity issue or not, but felt that it would probably fix it. He said everything seemed fine across the coil, and that the CFM issue was the only real thing he could find. Of course, i'll get a 2nd opinion before committing to that kind of work on a fairly new system. Any ideas on my humidity problem? It's usually 34% or so at work with a pretty old system on 73 degrees. No matter what I set mine to I just can't get below 50%. I'm worried about mold issues, and why mine won't dehumidify in general. They lowered the blower speed from high to med-high to try and get it colder across the coil, but it didn't seem to help. I think he was saying because of the airflow issue he couldn't charge it as much as he thought it should be

50%RH is acceptable for mold control. Occasional 55%RH is not a problem. 90^F, 40%RH is much wetter than 75^F,50%RH. Check for the ^F dew point or grains of moisture to compare moisture content. Dallas outdoor dew points about 70^F, inside should be 50^F. Sucking in hot outside 70^F DP air makes your house wet. Watch for rainy cool weather! the a/c does not run much and the home gets wetter. Slowing the air flow makes the cooling colder removing more moisture. Cold air makes the grills and drywall around colder, causing condensation from the surrounding humid house air. Clean the grill/drywall soap/water. If wet for several days, mold will return. There must be times when your home is wetter than 55%RH, like this spring. A/C removes 100 pints of water on hot day. On a wet cool day, only a fraction of the moisture is removed. A 100 pint whole house dehumidifier will maintain <50%RH without any a/c operation. We manufacture the Ultra-Aire and Santa Fe whole house dehumidifiers.
Commercial buildings with internal heat gain from lights and equipment being cooled by near freezing cooling coils may provide lower relative humidity. RH meter are very inaccurate at very low or high %RHs.

[beenthere]

I think theres a fee you have to pay for it to work.

If your systems are over sized, it would be a replacement of the outdoor unit, and maybe the indoor unit.

Has keeping the downstairs warmer made a difference.

[hvac_help_needed]

I am a homeowner not a professional but had very similar issues 2 yrs ago. Everyone on this forum helped us.

My opinions...

1. check duct work for leaks as a leaky supply will create negative pressure situation in your house causing outside air to be sucked in constantly (been there)

2. get 2nd opinion on air flow problem, but i would think not enough air flow over coil would cause it to freeze up and you would see this on very hot days when it is running alot, esp. if set at 72. Do you see evidence of freezing up coil? (been there too)

3. as teddy bear said, you cannot compare outside humidity to inside. 90° and 35% humidity is relative humidity, water in realation to temp. When air is cooled the relative humidity goes up, because warm air holds more moisture than cool air.

4. seer rating...I thought i remembered reading a couple of years ago that many professionals felt this to be a big issue with dehumidification...higher the seer, less ability to dehumidify?? (been there also, I thought)

5. I too live on a slab. Have no idea if this contributes, but have to wonder.

6. We learned that it paid off for us to monitor RH in our home year round!! If humidity gets high, everything in your home holds the humidity. We could feel it in our carpet. We purchased a standing dehumidifier, and run it to keep humidity below 50%, ideally 45%. Whole house ones were too expensive for us. We run it in spring when a/c does not. We run it nightly since a/c does not run much at night, and keep house temp at 75°.
Its perfect!

[opti]

Thanks guys. I have the downstairs at 77 and the upstairs at 72, it's been keeping the upstairs running pretty long, but I haven't seen much of a difference. How do I check for duct leaks? I know I have a problem with my backdoor. It doesn't have any porch/ or covering at all, and the builders did a crappy job, I think the trim and frame is more caulk than wood. It's a terrible fit, and not sealing at all. I have someone coming to replace the door and repair the frame next week. Per a suggestion here I stopped by Sears to get a 50 pint dehumidifier. Salesman was pretty shocked, they don't even carry them in store here because they don't sell any. It should be here Tuesday. Is that little guy going to be able to help the whole house, or am I going to need one per floor? Right now according to my Radio Shack atomic clock/weather station it's 48% uptsairs and downstairs, but my Radio Shack little digital hygrometer I had for my cigar humidor is reading 52%. This is with all my exhaust fans (2 downstairs, 3 upstairs) running since yesterday morning.I hope the weather station is more accurate . It's usually lower like this in the morning, then climbs during the day. I emailed off for pricing on the Ultra-Aire, but I have a feeling it's out of my price range. I'm really hoping a cagey AC vet can do some magic and wrangle some more dehumidification out of my AC. The problem seems to be finding one.

[opti]

Originally posted by hvac_help_needed
I am a homeowner not a professional but had very similar issues 2 yrs ago. Everyone on this forum helped us.

My opinions...

1. check duct work for leaks as a leaky supply will create negative pressure situation in your house causing outside air to be sucked in constantly (been there)

2. get 2nd opinion on air flow problem, but i would think not enough air flow over coil would cause it to freeze up and you would see this on very hot days when it is running alot, esp. if set at 72. Do you see evidence of freezing up coil? (been there too)

3. as teddy bear said, you cannot compare outside humidity to inside. 90° and 35% humidity is relative humidity, water in realation to temp. When air is cooled the relative humidity goes up, because warm air holds more moisture than cool air.

4. seer rating...I thought i remembered reading a couple of years ago that many professionals felt this to be a big issue with dehumidification...higher the seer, less ability to dehumidify?? (been there also, I thought)

5. I too live on a slab. Have no idea if this contributes, but have to wonder.

6. We learned that it paid off for us to monitor RH in our home year round!! If humidity gets high, everything in your home holds the humidity. We could feel it in our carpet. We purchased a standing dehumidifier, and run it to keep humidity below 50%, ideally 45%. Whole house ones were too expensive for us. We run it in spring when a/c does not. We run it nightly since a/c does not run much at night, and keep house temp at 75°.
Its perfect!

How big is your home, and how big is your standing dehumidifier?

What do I look for to see if my coil is freezing?

for my SEER rating, not sure. It's a Bryant 2.5 ton , outdoor piece has a model # 563cn030-B. There's no marking on the inside unit other than Bryant, but a sticker on the big box piece taped to the furnace has a label- 'Allstyle Coil " mode # ASFW363622T, 300psi R-22.

Now, on the warm air/cold air humidity thing . What's the ideal temp/humidity indoors? I can get the temp from 78 to 72 and the humidity doesn't seem to change much if at all. Time of day seems to make more difference than anything. It's usually just under 50% in the mornings, and climbs to 52-53% throughout the day. 74 is about the most comfortable for us, but I'll go up or down a bit if that helps at all with moisture content.

[j-bill]

50% RH - 60% rh is good ,working in the most humid tpabay area & seeing loads of mold & mildew calls,what you describe is not humidity problem if your house is tight & closed up all the time, you can't expect the same outside as inside,your lower than normal airlow will actually perform better dehum(though a problem).call a reputable co. and try to get a lead tech out to make sure you have clean coils-blower proper metering device if piston,proper superheat& subcooling,airflow. if they are clueless about or can't test humidity or anything listed here, give'm the boot!expect a 1-2hr. service call for the 2 systems.

[hvac_help_needed]

opti

our home is almost 3000 sq ft. It is a 2 story, with 2 rooms with 2 story ceilings, one room with cathedral ceiling, and 9 ft ceilings entire 1st floor so there is alot of cubic air.

our dehumidifier is a 70 pt. standing purcgased from sears for about $200. Basically we run it when we know the cooling is not going to run as much, like nightly, and when weather is cool and damp like early spring.

We knew our coil was freezing because you could see the condensation leaking from the bottom of the furnace when the a/c shut off and the coil began to thaw!

I do not know much about Bryant systems. And I just threw the seer point out there to see if any others in the field would elaborate.

As for temp/humidity, it is a matter of personal preference, but anything below 48% rh in my home feels good. I try to keep it 45-46% by running dehumidifier at nite and a/c during day. 75° and 45% rh is extremely comfortable. I have been told by many respected service people that 60% rh is common in homes in summer, and some service people feel that should be tolerated.

I do not understand running your exhaust fans. This creates a negative pressure situation in your home, and in order to equalize the pressure, outside air gets sucked in, creating more humidity issues. I would turn them off.

I find it interesting that your humidity increases throughout the day...mine is opposite. But I do recall this happening when our coil was freezing up....as it thawed it basically acted like a humidifier as air blowing across it dried it and blew moisture back into the house. Are you running the fan in the ON position?

[Edited by hvac_help_needed on 06-28-2005 at 07:08 AM]