In Central KY. built a story and half home. aprx 2400 down and 1800 up(includ over garage). Lived here 6 mos. Have 2 hvac units made by Tempstar. Upstairs is all heat pump, downstairs is heat pump with gas back up. Upstairs is fine. Downstairs unit worked fine until 3 weeks ago. When the D/S unit was working well, the thermostat would be set on 75 and it was very comfortable even during hot/humid weather.
Now humidiity indoors is high. Hygrometers bought at local stores vary up to 25% on their readings 40-50 % on one and 60-75% on other. Either way it is far too humid in the house and there is a damp odor too. Have reduced the thermostat to 72 to make it run longer, which makes it uncomfortably cold. The service man reprogrammed the fan to blow less air for a longer time to remove more humidity. Didn’t work at all. The duct work in the crawl was dripping wet. Ran a fan on it for 3 days & dried it our. Have a vapor barrier on crawl floor which is in good shape(dry) and the house is pretty well vented. The crawl had a damp smell but there is very very very little evidence of water intrusion, only a 2″ damp spot in a couple of corners and one other place on block walls and no dampness under the V Barrier. No actual seepage. Seemed to me that the condensation on the system was contributing more water.
as a last resort I am using a dehumidifier in the house and getting several gals per day. Seems the system is just recirculating damp air?
Replies
There's a drain on the unit to take away condensate. Is this plugged-how that would introduce water into the system I don't know.
Do you have a humidifier on the system that is somehow adding moisture to the air?
Open crawl vents in a conditioned space, with metal ductwork is ripe pickings for condensation forming. I suppose any openings in the duct that could pull warm moist air in could cause condensation on the inside of the duct.
There's a lot of moisture in a new house. Imagine for instance the water in plaster/joint compound and the latex paint put into a house. Not suggesting in the least this would produce the volume you have.
A great place for Information, Comraderie, and a sucker punch.
Remodeling Contractor just outside the Glass City.
Quittin' Time
Edited 7/30/2006 4:49 pm ET by calvin
The unit does not have anything to add humidity.
Bob858
New houses have a great deal of water in them.. The wood they are built with is about 19% water which will take several years to dry out completely. Add the moisture in the mud from sheetrocking, paint and other such sources and it's very common for a new house to be really really damp..
A/C makes the problem worse because you are recycling all that moisture..
Add a humid day and things can quickly overwhelm a house..
Dehumidifiers are a solution but as things get crisp this fall it will dry out once you heat it this winter it will quickly get under control..
(assuming no other problem)
"A/C makes the problem worse because you are recycling all that moisture.."Now in the hell does A/C "recycle" the moisture.Lets see some points ont psychrometric charts.http://www.sp.uconn.edu/~mdarre/NE-127/NewFiles/psychrometric_inset.html
"Now in the hell does A/C "recycle" the moisture."
It does not as you already understand. I doubt if Frenchy has ever seen a psychrometric chart, much less posses such, and obvioulsy has no clue about the data contained within.
In additon to the condensate drain being plug, where is does it drain to.
If the drain is plug or leaking into the house or just terminated some place that is not outside (or drains to the outside) then it will be wetting something in the house.
But most likely the problem is as Calvin mentioned. If the crawlspace is vented then you letting in warm moist outside air and the crawlspace is cool and the ducts ever cooler.
Here is the weather in Lexington from May 1 to today.
Look at the dewpoint on the chart. It has been general building with it averaging 70 or better since the end of May.
That means that any duct work that is below 70 will get condensation on it during that time.
http://www.wunderground.com/history/airport/KLEX/2006/5/1/CustomHistory.html?dayend=30&monthend=7&yearend=2006&req_city=NA&req_state=NA&req_statename=NA
Like they said see if the drain is plugged. If not check to see if some part of the return air duct has fallen apart or a panel is loose and is letting out side air in. the system should be circulating air from inside the house for the most part. A smoke candle should show you where the air is being drawn in to the system.
Have you had any rain shortly before you noticed the problem? Do you have a leak around the windows, doors or in the roof?
no leaks that are visible. I have walked the house inside and out and paid close attention to anything that could or would suggest a leak. There was a big rain back a few weeks ago. The crawl seems pretty dry-no water on top of the crawl vapor barrier that would suggest water coming from a plumbing leak nor is there any evidence of water under the vapor barrier. The hvac drains to the outside via a gravity/daylight drain that runs under the footer 30 feet out and beyond the perimeter of the house, a minimum of six feet drop from the house outward.
I will check the drain and make sure it is not plugged. Thanks for your help.
Bob,
Are you sure your AC units are not so oversize that they only run infrequently. That is a real posibility in todays tight & well insulated homes. The inside of the house will feel clamy.
Try setting the AC to run the fan continuously to see if that makes it more comfortable & maybe only run the compressor on the upstairs unit.
This could give you a feel for need to down size AC units.
thanks for your suggestion. I think maybe it may be oversized. The hvac guy is having the sizing recalculated and has said that he'd replace it with a smaller unit if the mftg suggests doing so. He has adjusted the variable speed fan to blow longer and slower to make it run longer. He has reduced the amount of freon to reduce the temp of the air so it will take longer to cool down, both of which have helped but not solved the entire problem. But I am still running a dehumidifier indoors to compensate for the indoor humidity and keeping the thermostat down. The variable speed blower runs continuously-however I tried it on automatic and noticed no difference.
I have a fan blowing in the crawl and all of the vents shut and it has helped the condensation on the supply line, except in a few places, especially those where the floor insulation rests on a supply line(in some cases, but not all). There strangely enough, the insulated supply lines are damp where the insulation and the supply touch. Thanks so much for your suggestions and willingness to help. I sure need it.
Bob, you didn't say if you're foundation is vented, or not.If it is, you might want to try closing them, and running the dehumidifier in the crawl space...if that helps, put ridid foam in the vent holes, then seal them with spray foam, forever...I've also seen this happen when the top of the foundation isn't capped and/or the top blocks aren't filled...You may also want to consider conditioning your crawl...
I need a dump truck, baby, to unload my head
the crawl is vented along the foundation. I open the vents when the humidity is low and shut them when high. Just started this in the past few days.
I open the vents when the humidity is low and shut them when high. Just started this in the past few days.Is that helping? I need a dump truck, baby, to unload my head
"the crawl is vented along the foundation. I open the vents when the humidity is low and shut them when high. Just started this in the past few days."WHAT DAYS HAVE THE HUMIDITY BEEN LOW?Here is the dewpoint from July 1.http://tinyurl.com/lf2qtExcept from July 6-10 the dewpoint has be near 70. Even the lowest point after that (july 24) where the dewpoint was 60 that is moist enough that you might have gotten condensation on the ducts. And even if it did not condesnate then RH in that cool area would be high enough for mold.
Understand your problem. I had a 3 story once(1-1/2 & full walk out below) it had seperate furnace-A/C for each floor. Fortunately 2 were side by side so we tied the duct work together and only ran one unit most of the time.
Then we put a box fan blowing into a clothes chute from the lowest floor & exhausting onto the 3rd floor. It ran all the time & really improved comfort on all 3 floors.
You say you are getting condensation on the outside of the ducts in crawl space. Is this attic (under the eaves) or under the floor crawl space.
If under the floor there are threads on Breaktime & in FHB on insulating the exterior crawl space walls & conditioning the whole thing.
If in the attic it sounds like your ducts are not adiquately insulated. If so you would expect condensation on outside of cold A/C ducts. Consider foaming them.
Jim
this is in the crawl. have no problem upstairs in the attic
Bob,
If you are getting that much moisture in the crawl space you should probably look into conditioning it. There have been articles in FHB about that. Probably messages here also.
1) close all outside vents into the space.
Following I think is also reccomended. But check around.
1)Cover the soil with black plastic & tape joints.
2)Line the stem wall interior with Foam insulation & tape joints.
Jim
that statement about reducing your freon to make your unit run longer sounds really wrong to me.if a unit is that oversize it's time to get a smaller one.it sounds like your hvac guy knows what he's doing,but what little i know of ac is if you have a frozen up a coil with no air passing thru you have either a stopped up filter or your low on freon. your a coil is not freezing up with this lower freon level is it? thus low air movement = more humdity larryhand me the chainsaw, i need to trim the casing just a hair.
"that statement about reducing your freon to make your unit run longer sounds really wrong to me"
As it does to me.
"sounds like your hvac guy knows what he's doing..." Absolutely, NOT.
Bob, this is an inappropriate way to "adjust" the capcity of your system. Consider this a big red flag. This is the equivalent of removing spark plug wires from your car's engine to control speed. A properly charged system always performs better than an improperly charged system. I would question this HVAC guy on the effects and warranty implications. I would also have them commit, in writing, to refurbish all removed freon at no additional cost to you when this bad idea pans out. Personally, if I were not committed to this contractor, I would have no further business with them.
You may want to check out this solution to your problem, and it may save on your electric bill:
http://www.aprilaire.com/pdfs/800.pdf
The folks at http://www.buildingscience.com like it.
Billy
I will address this with the hvac tomorrow. thanks so much. Curious. Should a 4 ton unit have more freon than a 3 ton? Because he loaded the 4 ton to the same poundage as the 3 ton?