Two different contractors had the luxury of walking around,testing and looking it over,would I not be a miracle man if I told you what's wrong without even knowing what brand the unit is?????? The return air has bad leaks and most returns and supplies are not well enough insulated. NEXT PLEASE !

Wow, ok, then. I was not so much looking for a solution, as wanting to talk a little HVAC theory - it seems like the usual suspects have been ruled out in my case. FYI, returns, ducts, etc. all tight and super well insulated. Thanks anyway.

Oh, and it's a Lennox.

It is likely oversized. We did not live here when it was installed, so don't know the details, except that the family member who did was really impressed with all the measuring, etc. that was done.

What I don't get is why, when I have it set low enough to run continuously for most of the day, the humidity doesn't drop at all?

Part of the solution to the initial condensation problem in the attic is a dehumidifier. Attic humidity is well controlled - ~50% - so why is there so much condensation on the bottom of the air handler?

I'm just frustrated; there has been so much money sunk into this thing already, and I am at a loss. Wanted to get it straightened while it's still hot - may just wait it out till it cools off and pick back up next summer. If the thing even comes on then, ha!

A little hvac theory huh? For now, I'll take your word on ducts being in good shape but if you are relying on installers say so,I have to be sceptical considering their in-ability to fix your problem. My guess as to why there's so much condensation on bottom of of air handler is because insulation is wet in floor of handler. Some of that water might be leaking but wet insulation conduct's heat well enough to cool metal exterior and cause sweating. Without examining system I would say major contributor is one or more of poorly installed evap coil,condensate pan,condensate drains,oversize blower,blower speed too fast. One or more of those will cause condensate to be carried off coil in air stream where some is deposited inside handler and remainder is carried into liveing space. Insulation inside of a properly operating system is dry since condensate run's down coil into pan then out drain. It should be simple to pop a panel to see if inside is wet. Figureing out why it's wet and knowing what it take's to correct it is what might seperate the men from the boys. Based on scant info furnished,that's about all the theory I care to dabble in right now. Give us some numbers for air flow and refrigerant pressure curves along with inviromental conditions and maybe we can suggest additional things to look at. If bad come's to worse we'll see if Austin Air will roll out the ol crystal ball.

Sorry Klem, Humidity control or lack there of isn't covered in the 'ol crystal ball' spectrum.

Temperature and Humidity fluctuate between themselves. You can have up to 100% humidity (out side) at nearly every temperature. This humidity can find ways into your home.

Your AC can produce humidity due to improper drainage and long blower run times. Equipment Sizing (tonnage), just as much as proper drainage can have implications on humidity in the home.

Your attic ought to be separated from the living space and the insides of the new HVAC system both for airflow and with insulation/vapor barrier (in the ceiling and between inside of the ducts/air handler and the attic). Putting a dehumidifier in the attic seems like a high-cost-of-ownership (power bill) bandaid that doesn't really fix the problem.

I wouldn't discount the suggestion that you have leaks in the new ductwork. The insulation and jacketing could appear to be well sealed, but if rigid ductwork (for example) doesn't have its seams and connections (under the insulation/jacketing) sealed with mastic/tape, you could still have a pretty leaky system. Same goes for the air handler itself. Another place to look at are the register boots- are the seams in these sealed and are the penetrations sealed so that they don't create an air path to the unconditioned space?

If you wanted to rule out leaks in the ducts and air handler, you could get a blower door and/or duct blaster test done. This would help you identify if there are leaks in the new system. A blower door also would show you other places that need fixing in the house. I'm thinking there's also a chance that, if most of the return air is pulled from one part of the house, other air leaks there could draw in unconditioned, humid air from the attic/outside/crawlspace/etc.

In theory, if the system is running a lot trying to reach setpoint, it ought to get there if sized properly and also reduce the humidity. For what it's worth, 68F is a pretty low setting if you're somewhere that's much hotter than that outside.

What is your location, what is the size of your house, and what is the size of the AC condenser?

The this an unfinished attic? Is the attic sealed? If it is not, does it have good ventilation?

What is the outdoor humidity when the indoor humidity is in the 70s? How tight are the windows and doors of the house?

Thanks. Yeah, it gets to temp easily but the humidity doesn't go down. Humidity actually seems to increase, the more/longer it runs. It is actually often less humid in the attic where the unit is than in the second story that it conditions. Blower door test is a good idea.

I'm in Arkansas - hot and humid.

Unit is for upstairs only, appr. 1900 sf. 4 tons, so, yeah, probably too big. Attic is floored, not finished, well ventilated including thermostat controlled electric fan vents.

Outdoor humidity ranges from 50's to 100 - if unit is running frequently, it's pretty much in the 70%'s or upper 60's humidity.

Windows all have tight storm windows. Doors weatherstripped, could probably be improved but I wouldn't call them drafty. Downstairs, where the doors are, AC and humidity control both good with another unit.

Edit, if it matters, none of these problems existed with the old unit.

"Humidity control or lack there of isn't covered in the 'ol crystal ball' spectrum."

Aww shucks,and it's always been such a trusty old ball. No matter though,I conjured up a vision of the unit and figured it out. The metering device is at fault don't you see? Couldn't quite make out the numbers on it because old age and Jack Daniels soaked up while conjuring caused blurred vision. The coil is alternating between cooling down,freezing up,thawing out to make a mess then repeating the process again and again.

Klem1, now this is a good way to put the 'ol crystal ball' into extinction by giving away secrets of what the ball is filled with.

# Jack Daniels.

Stop cracking the balls open to get at the magical fluid that causes you to forget / not care about things.

Although now that I think about it this might be the cheaper solution overall?

Wow, the Jack really improved the situation!

On a side note, if the coils were freezing, it would not cool during the frozen periods, correct?

" if the coils were freezing, it would not cool during the frozen periods, correct?"

Correct.

On another side note,I put the Old #7 back in the ball after it had been aged another 24 hours,called it Single Barrel then sold it to some Nigerians on CraigsList .

I don't undertand your basics, OP. The attic is sealed and coupled to the living space, or vented and coupled to the outdoors? You have a dehumidifier there so indications are that it is sealed from the outside. On the other hand, what do you mean by "Attic is floored, not finished, well ventilated including thermostat controlled electric fan vents."? Where are the ducts and the HVAC unit, inside or outside your house envelope?

If you have an vented, open attic with power vents and air leaks to the living space, you might be depressurizing the living space leading to sucking in a lot of humid air. If you have this layout, the first thing I'd recommend is unplug the power vents and see if that improves things.

'If the coil were freezing there would be no cooling' Yes and no. It depends on how frozen the coil is, how far away the area you are trying to cool is.

It will still cool, just not adequately. Frozen coils are a capacity problem. As the coil freezes capacity of the system is reduced. The farthest areas or warmest areas of the home will feel it first and then as the coil freezes completely the temperature will rise in all areas because no air flow at all thru the frozen coil.

good post Ionized, looking forward to the reply from OP.

Ah, sorry, I thought I had replied, but forgot to enter, I guess. Attic is well vented to outside.

Humidifier was placed when attic was more humid than outside in the midst of the initial attic condensation problem. Attic is always less humid than the second story conditioned space with the humidity issue.

My HVAC guy came Friday, he mentioned the possibility of a sticky coolant valve - it has a name that escapes me...

Cooling has not been a problem at any point - just the blasted humidity.

I appreciate all the input and y'all talking this over with me.

"My HVAC guy came Friday, he mentioned the possibility of a sticky coolant valve - it has a name that escapes me..."

Hells bells,Klem was out Thursday and even in a state of dipsomaria,told you that much. Sticky coolant valve "aka,metering device". The name that escapes you is probably "expansion valve".

Yep, expansion valve. "Metering device" was not in my vocabulary. Got it now. :)

*passes Jack*

The attic is well vented in a climate that is humid and you have a humidifier running in the attic running 24/7 trying to lower the humidity? Do you see a problem with this set up?

Have you measured the humidity in the attic with a hygrometer? Take some temperature and humidity measurements in various parts of the attic. I think you will find the humidity much higher than when you are close to the dehumidifier.

Attic humidity was HIGHER than outdoor humidity after this monster unit was placed. I have constant humidity measurement indoors, outside, on the dehumidifier and have used a hygrometer. I know it seems wacko, like trying to dehumidify the outdoors.

DEhumidifier in vented attic? how is that supposed to work, dehumidify the

world? you need some problem solvers to evaluate your situation, not

more trades throwing your money away.

its not there to make attic humidity lower than the outside - it's there so the attic humidity is not higher than the outside. . It was placed when the attic was totally wet from an oversized unit coupled with undersized ductwork, to help dry things out.

Agreed, it's not a permanent solution to anything, and I look forward to getting rid of it.

Really hoping the promised hot temps happen later this week so it can be investigated more.

As an aside, the company that is currently working on it did not place the unit. They did fix the ductwork. Since then, they haven't charged me at all while they've been tweaking fans, flushing drain lines, etc trying to get the thing to act right. The owner was here Friday and seems determined to fix it.