Leaking AC plenum

[President Baboon]

Hello, nice place you've got here!

I found an air leak in my AC system, and I am trying to figure out what next steps are. My air handler is located in the garage (Florida, 1994 construction). It appears that the plenum (correct term?) was not originally part of the system, but I have seen similar configurations in other houses.
There was also some weirdness in the return ductwork and where it comes out, but no leaks felt here:

The leaks are called out by green marks next to them:
Front Left Face. This one is substantial and is the reason I realized I had a leak. I can feel substantial cool air blowing out of this whenever the AC is on:
View attachment 1483143 Left Side, corner next to air handler. Multiple small leaks:

Behind the air handler. I am not sure if this is leaking or if it's cumulative effect from other leaks:



What is wrong in these pictures and how can I fix it? The hot water heater is present to the right of this unit so I don't have a lot of space to work with. Thank you in advance.

 

[Terry D]

I would try some silicone or foil tape. The gap in the drywall where the return goes in the ceiling is not a issue, its just cosmetic.

 

[Dumber than lumber]

That is some real half-way done duct work. They decided they weren't building a piano, you could say.
If there are no leaks at the ceiling, I would still want to seal it to keep out bugs, and lizards, etc.
Where that long green bracket line is drawn - I would be inclined to get behind that drywall for a look. I mean, did they cheap out and scrimp on ductboard? Maybe cut a few peepholes and see what the overall ductwork and sealing of edges look like. Could be lots of leaks and other shortcuts.
And welcome to the forum.

 

[President Baboon]

Thank you both and for the welcome. I was not happy about the ceiling but more wondering if it indicated more serious failure.

I think I can just take off the whole slab of drywall board and look in there - it's completely unsealed. Is it considered standard to line the cavity of that plenum space with duct board? If that wasn't done, I'm assuming I need to make sure that's what goes back in?

 

[karoc]

Being in trade for several yrs I have seen worse, believe me yours is not bad. But it looks like your duct is made with duct board which is not the best but it is use in a lot of homes, which over time it will settle and separate from mating piece. As others saying caulk, foil tape and can spray foam will help seal leaks. But it will need to be clean before you get started or it will come off again or won't stick. Over the yrs if your blower wheel get little out of balance due to piece of paper being **** in or piece of insulation on wheel will cause it vibrate then cause separation. So nothing new, I bet that most of houses in your neighborhood may be in same condition if about same age and built by same contractor. No worries

 

[President Baboon]

Pretty sure this is aftermarket. The plans show a different layout of A/C condenser, different placement for water heater, etc.

So yesterday the system started blowing warm air. Possibly just frozen over, but not really sure. Anyway, I removed the drywall. There is in fact ductboard in there. Not really sure where the leak is but I can feel air rushing out - previously I think the drywall was containing it except in those couple of places. Now there's more area for it to escape through so I can't feel a precise exit location.


I also checked the drain line this morning. There was slimy white and red **** in there so I used a shop vac to **** out the line. Then I decided to open the condenser. What's this?
Le soupe du grenouille, monsieur? Liquified frog in the condenser. That was pretty gross. There's a UV light but the ******* who installed it just let it dangle instead of modify the bracket to fit properly.

Here's the rest of it, so maybe someone who has more A/C experience can tell me what other mistakes to look for.

 

[Terry D]

Someone defiantly took the cheap way out when building that return air box. That is you evaporator. The condenser is the unit outside. I have seen UV lights in the supply plenum, never down at the evaporator. Is it leaking air where the air handler setting on the return air box. did you get the problem fixed for it not cooling.

 

[rlitman]

Someone defiantly took the cheap way out when building that return air box. That is you evaporator. The condenser is the unit outside. I have seen UV lights in the supply plenum, never down at the evaporator. Is it leaking air where the air handler setting on the return air box. did you get the problem fixed for it not cooling.

UV on the evaporator is used to keep the coil clean from mold. In the plenum, it is used to sterilize the airflow.

 

[Terry D]

UV on the evaporator is used to keep the coil clean from mold. In the plenum, it is used to sterilize the airflow.

Ok. Thanks

 

[President Baboon]

Okay, so I got my terminology slightly wrong. I was not surprised to see UV here, but the mounting is for .
To be clear, I was looking in to the air leak while the A/C was functioning normally. It's leaking air from around the merge and (if you go back the original post) the top left corner of where that drywall was placed. However, it's begun to behave erratically.

Also, what does a return air box that is not the cheap-way-out look like?

 

[Terry D]

Okay, so I got my terminology slightly wrong. I was not surprised to see UV here, but the mounting is for .
To be clear, I was looking in to the air leak while the A/C was functioning normally. It's leaking air from around the merge and (if you go back the original post) the top left corner of where that drywall was placed. However, it's begun to behave erratically.

Also, what does a return air box that is not the cheap-way-out look like?

Hope I didn't offend you, but as already said, duct board isn't the best choice. It cant support the weight of the air handler, so a wood frame has to be made. The tape can fail and start leaking. I have seen boxes made from plywood and the seams sealed from the inside that were ok. To me the best are made from metal. Some will have a metal frame inside to support the weight. Some are custom made and you can buy some off the shelf, but you are limited on the size

Lennox 51W00 Return Air Base Kit, 24.5"

Buy this Lennox 51W00 Return Air Base Kit, 24.5" now from your #1 source for OEM repair and maintenance products at HvacPartsShop.com

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https://www.lowes.com/pd/Winchester-20-5-in-x-21-in-x-28-in-Return-Air-Box-Assembly-Duct-Plenum/50238747?cm_mmc=shp-_-c-_-prd-_-plb-_-google-_-pla-_-171-_-sosyearroundheating-_-50238747-_-0&placeholder=null&ds_rl=1286981&gclid=CjwKCAjw3MSHBhB3Eiw

Alpine SBFD30-100-244 30 Inch Wide Return Air Support Box and Plenum Kit With Filter Slot

www.alpinehomeair.com

 

[President Baboon]

No offense was taken. I misconceived that component as being the condenser.

Given that there is already a wooden frame around the airbox that has been sealed (poorly) to the air handler/evaporator with mastic, I'm wondering how I would go about sealing a leak that I can't see (I can feel air, but not exactly where it's coming from).

On that note, would I need to disassemble the box whether I were to repair the ductboard plenum or replace it with a metal one?

 

[Terry D]

That box is supporting the weight of your air handler. You would have to remove the air handler or try to support it to remove that old return air box. You can try just to remove the front 2x4's from the box leaving 3 sides, then remove the front duct board. You then should be able to see what is going on inside as far as leaks

 

[President Baboon]

Okay, thank you for the info. That's at least a weekend job. I'll update when I get it further apart.