Home HVAC advice needed

We live in north central Florida, in a house mostly built in 1937. It is insanely hot and humid here. 3 years ago we had an entirely need HVAC system installed, including all new duct work and additional returns installed. The air handler is in the attic. They replaced a 5 ton system with a 4 ton system, based on their system analysis.

Subsequent to that, we had a new roof installed, which included ridge vents, in order to duct the attic more effectively.

Ever since the AC was installed, we've had condensing issues. So much so that the system kept tripping the float switch. Eventually they installed a 2nd drain, this one in the side of the drain pan, in order to prevent the drain pan from filling up and tripping the switch.

Initially the contractor, who came highly recommended, claimed the attic was simply too hot and that ridge vents would help. They did not. Since then, the story has been that the system is functioning normally and the level of condensation is commiserate with the conditions. Given that the previous unit, which was having other issues, never condensed like this one, nor did the unit we had in our attic in our previous house, I believe something is wrong.

Fast forward to last night, when my son notice discoloration on his bedroom ceiling. I went up in the attic and, while I couldn't see an active link, the pan was only a hair below the float switch and was, once again, covered in water. Pictures below.

One of the company techs came out and found the bottom duct board in the outflow duct is wet and soft on the bottom. He surmises that the system is pulling so much condensation through that the duct board has failed and is leaking.

I also found what seems to be a large gap in the same area where the duct board has gone soft and wet on the bottom.

So, hive mind, is the system working properly and simply condensing as expected? Or am I being fed a lot of crap? Is the gap on the side an issue or just coincidence?

Not an HVAC guy but we went through this in wpb in the 100 year old house. One of many things we did was make sure that the fan was running longer when it turned on. Short cycling won't remove enough humidity from the air. 2nd, are your soffits clogged? Roof vents work effectively in combination with soffits. 
With all that said- you do live in a swamp. 

I have an air handler in the attic of my '57 and I don't have any condensation on it at all. Something is up with the air handler. Did they have to take it apart to get it up in the attic? Did they put the insulation back inside the metal box?

The smaller tonnage will give you a system that runs longer and more often. That will keep the humidity in the conditioned space where you want it.

Go put a wet vac on the drain line outside and pull all the water out of the pipe. You can wrap a wet rag around where you put the vac hose on the pipe outside to seal it and draw good vacuum. This will help you determine if it's a drain problem. Do you have a bleach injection system of some type in place?

Newer units do remove more moisture. But irregardless it shouldn't be filling the pan. There should be a clear, downsloped drain pipe from that pan to outside the building before the pan can fill and hit the float switch.

Get a second opinion from an HVAC Specialist. 

In reply to dyintorace :

So how many SF is being conditioned?

My initial reaction was that the size of the a/c system was just too large.

Is the air handler also adding outside air (make up air) into your system?

You might need to add a basic exhaust fan to pull humidity from around the air handler. It seems odd to have to air condition your air conditioner but sometimes that is the only way. 

But I think regardless the system should be insulated properly which is hard to figure out in your photos. Condensate management at the coils to the drain should be confirmed to be in position.

This is a situation that may need a full rethink. System size, blower speed, ventilation of attic, drain pan options, duct insulation, all have to be balanced to maybe fix your issue. 

..sorry you're going through this. I don't know the entire solution but I'd start with blowing/vacuuming out the condensate drain.  

When I lived in FL the condensate drain pipe would get blocked with algae and they had these little "pills" that I had to feed into the piping to keep it clear.
 

First, sorry to hear you are going through this. 

If the drain pan is filling up, it needs a better drain.  Either your drains are insufficient, or they're clogged.  Nasty stuff will accumulate and grow in condensate drains.  Ensure the integrity of the piping, then blow them clear.  Periodically run a bit of bleach through the drain to keep stuff from growing.

Anything in the non-conditioned space that gets cold needs to be insulated and sealed to prevent humid air from touching the surface.  If you see condensation on surfaces in the attic, they are most certainly not insulated well enough. 

It looks like the air handler is condensing on the outside of the unit? That's pretty odd. I'm coastal in SC with all the humidity in the world and haven't run across that issue. The case and overflow pan on my attic-mounted air handler stay dry. 

You should have two drains. One from the air handler itself, and one from the overflow pan below the unit. The overflow pan under the unit should almost never see water unless the coil drain is stopped up. Alge will stop them up on a fairly regular basis without some kind of treatment. We use a chlorine tablet. 

This is the air handler in my warehouse at work. The top PVC is the air handler drain that goes outside. The bottom piece with the valve is the overflow drain. In a properly installed unit, that pan should stay dry. 

I would say you have either a stopped-up coil drain, a poorly installed unit, or someone stripped all the insulation out of the case when they moved it to the attic.

I would start with the drain. Get it blown out and drop a couple of chlorine tablets in it to keep it clear. If the overflow pan doesn't stay dry, then I would have a serious discussion with my AC company. 

Toyman01 + Sized and said:

It looks like the air handler is condensing on the outside of the unit? That's pretty odd. I'm coastal in SC with all the humidity in the world and haven't run across that issue. The case and overflow pan on my attic-mounted air handler stay dry. 

You should have two drains. One from the air handler itself, and one from the overflow pan below the unit. The overflow pan under the unit should almost never see water unless the coil drain is stopped up. Alge will stop them up on a fairly regular basis without some kind of treatment. We use a chlorine tablet. 

This is the air handler in my warehouse at work. The top PVC is the air handler drain that goes outside. The bottom piece with the valve is the overflow drain. In a properly installed unit, that pan should stay dry. 

I would say you have either a stopped-up coil drain, a poorly installed unit, or someone stripped all the insulation out of the case when they moved it to the attic.

I would start with the drain. Get it blown out and drop a couple of chlorine tablets in it to keep it clear. If the overflow pan doesn't stay dry, then I would have a serious discussion with my AC company. 

Thanks for confirming my belief, which is that the emergency drain pain is for just that - emergencies. The fact that the unit is wet all the time and that the pan is constantly full is indication that the system is not functioning as designed. Also, we're enrolled in the company's "comfort club" which includes 2 annual service visits. A technician was out ~1.5 months ago and ensured both drain lines were clear.

Will report back. 

in addition to what people are saying above, the ridge vent is hurting you, not helping.  It is allowing warm, moisture-laden air into the conditioned attic space.  I know the intent was not to have a conditioned attic, but with the air handler and ductwork in there, effectively that's what's happening.

In Florida you obviously have an endless supply of humid air to replace any moisture that the unit is condensing out of it.

So a few things....

First, the amount of  condensation on the outside of the air handling unit is in no way normal .  It's certainly not the first time an air handler has been installed in the attic of an older house, my upstairs unit is in a crawl space where the temperature is ambient conditions plus 15 degrees in the day time and no issues with condensation.  (I'm in MA, nowhere near FL humidity but still mid 70's dew points with 95 ambient in the summer a few days.)   That it's sweating enough to fill up the secondary drain pan to the point that the level is approaching the safety switch is a lot of water, not some random drip from a crack in the drain fitting.   

It's hard to see everything in the pictures but it sure seems like some kind of problem with the insulation on the inside of the air handler.  It's typically 1/2" to 3/4" fiberglass that's pressed and treated with a gray / black glue like stiffener and often covered with a black fiber face.  (Sometimes foil faced too.)   If you can look inside the fan access section without too much trouble and see if all the interior surfaces are covered that would be a good start. Also, saturated insulation isn't doing it's insulation job anymore so if the unit drain pan is not pitched properly or there's a leak / crack somewhere inside the unit it could contribute to what you're seeing.   See if it's all wet when you check the conditions.  If it's all saturated and there's water standing in in the internal drain pan that's not normal.

Did they put a trap on the drain where it connects to the air handler?   Most of these units have the fan in a "pull through" arrangement and if there isn't a trap the unit can hold condensate back inside when the fan is running.   Residential systems don't run a lot of static pressure fan wise so if there's an inch or two difference between the inlet and outlet of trap height ( to keep air from being pulled back in through the drain line / holding drain water back) that should be OK.   

It's a good thing that the contractor did a load calculation and reduced from 5 tons to 4 tons.   It's really important to comfort to have the unit correctly sized so it runs longer cycles to dehumidify the air.  Oversized units will cool the space down quickly but never dry the air out so it feels muggy.   That said, if there's no trap and it's holding all that water back during those long cycles....

Good luck, let us know what you find.

Most houses in Florida that were built before the 60's will have been retrofitted to have AC and the attic is where the air handlers usually end up. The other place is in the rafters above the garage.  Either location isn't ideal, latest construction methods put everything "inside the envelope" of conditioned space.  There is no way your air handler should be sweating that much.  I took a quick look at the temps of my attic at the peak with an infrared sensor and have 130F, not a drop on the metal box, not a drop in pan. The drain outside for the coil has a running drip like it should. All the duct work has either the foil insulation board or has built in insulation of about R-6.  With the hi temps in the attic I had blow in insulation put in up to R-42 over the R-13 stuff the house was built with.

You need to crack open the air handler and see if there is any insulation on the walls.

And if anyone is planning to build or modify a house in the hot humid south.. and you have other options.. don't let anyone put an AC system and ductwork in a hot attic.

Here's a link to a rabbit hole on the topic of AC and hot attics (from The Godfather of building science)

 https://www.buildingscience.com/documents/insights/bsi-077-cool-hand-luke-meets-attics

Thanks for all the insight gang. The contractor is coming out tomorrow for what sounds like major surgery on the cabinet. They're going to pull all the interior insulation, the coil, the motor, etc.

I'll provide an update after their visit!

How did it go?

OHSCrifle said:

How did it go?

So-so. They came out and switched out all the insulation in the cabinet. What they pulled out, at least on the bottom, was soaked through. They also found a hose that should have clamps on it but didn't. They suspect it was allowing condensation to drain inside the cabinet.

I checked it today and the bottom of the cabinet is still wet but less so. I'm going to check it again tomorrow. 

In reply to Duke :

Uh, no. The air handler and ducts should be sealed and insulated from the attic air. The attic is not meant to be conditioned space. 
 

I have an air handler and ductwork in my attic along with ridge venting. My guess is a combination of problems: clogged drains, poorly sealed ductwork, blocked soffit vents, crap insulation, etc...

tester (Forum Supporter) said:

In reply to Duke :

Uh, no. The air handler and ducts should be sealed and insulated from the attic air. The attic is not meant to be conditioned space.

In theory, theory and practice are the same.

In practice, they are not.