Hello! I was inspecting a new build today and was looking at this HVAC system. I have personally never seen a system done like this, but that doesn’t necessarily mean it’s wrong. The air handler is inside of a closet located in the laundry room. It looks like the return Plenum comes from the ceiling, but doesn’t go all the way to the unit. The air handler has an open bottom with an air filter underneath it. It basically looks like this whole closet sucks the return air in from the ceiling and into the bottom of the air handler. There was no gasket underneath the closet door. If anyone has any experience with an HVAC system installed like this, I would love to hear it!
Based on the pictures you have provided, my WAG is that all the return ducts meet up in the attic and there is a single large duct from that point through the ceiling and into the closet. Therefore, the closet itself is used as part of the return air ducting in this up-flow setup. No seal at the door? Not a big deal. The air handler will pull some return air through there as well. I just wouldn’t want too big of a gap where it would pull all the return air that way. The unit will by default pull air from the easiest place.
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Ty! I figured. just an odd set-up. Also, what does WAG stand for?
Wild Ass Guess, lol.
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Looks like a typical “take as many short cuts as we can” install. No pan under unit, not installed per manufacturer’s installation instructions, return air from closet… etc. Most common Carrier unit in this area are FB4 or FJ4 models. The label on the unit says the unit must be trapped as close as possible to the unit. Get the model number off the unit and check out the instructions.
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Perfectly normal. I see it that way all the time. Even my own home is set up this way.
As Ryan stated, all the returns tie into that one plenum. Just make sure all those ceiling returns dont have filters in them as well.
(I see that occasionally, and then its pulling through two filters before entering the AHU)
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agree
BUT, doesn’t make it right.
Here is a Plan for a similar HVAC closet (door opens on different wall)…
That is as screwed up as they can make it!
What kind of appliance hook-ups are in the laundry?
That filter at the bottom of the unit is a construction filter. It is not big enough for negative static pressure requirement. They do it, but it is not right.
Note: balancing the airflow of an HVAC system is critical for it’s performance. Balancing the supply air is the primarily concern for installers, but not balancing a return is the cause for failure and lack of performance.
What you describe sounds worse than what we can see in your pics. Got any more?
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No additional pics :(. It’s a Dr Horton new build so not a surprise I guess 
Up flow AHU. I see nothing unusual, except…no air filter and no air filter retainer assembly.
AHU, Up-Flow Air Handler Unit. Seen them in many configurations. Typically/normally/usually in that conditioning curculation configuration, there would be an air filter in a metal screen base at the base of the return duct where that yellow gasket is installed.
In condo the return filter, and the air filters retaining mechanical assembly, would be in the hallway ceiling in front of the entrance/egress door. The AHU mounted in the ceiling or a HVAC closet not far away.
Did you find a filter?
No filter means atmospheric particulate is returning on the supply side and all throughout the space.
He says there is a filter at the bottom of the unit. Up-flow configuration? What is the big hole in the ceiling for? is it pulling down from a ceiling plenum to the bottom of the air handler?
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I still want to know what’s going on inside of that laundry room! This closet is depressurizing and so is the laundry room. That stuff in the ceiling we can’t really see but that looks like something from outer space. Can’t say that it looks normal when you can’t see anything from here.
They do this AHU/furnace in an inside mechanical room here sometimes. It’s more energy efficient than leaving the unit in the hot/freezing attic, but it’s also noisier and wastes space inside. I don’t like it personally
That’s the return, which should have a duct that runs to the outside of the mechanical room or into a hallway depending on the install.
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So, in effect, the mechanical room is the return plenum? I thought we had moved on past this in the modern age 
Wait until they fill that room up with junk and restrict flow . Then wonder why the home is inefficient, especially when the dryer is running.
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Yes, my home is the same way. (but in a hallway closet, Next to the laundry room)
I am guessing maybe the OP is in FL?
I have a return duct in the hallway ceiling that jumps to the closet ceiling, and then the AHU pulls in air from there. I’m sure it works much better than starving the air handler with a louvered door..
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True, but only to the amount of air that can’t be pulled from a 20x20 hole in the ceiling.
But, you had a good point about what type of appliances they have. If it is a gas dryer, that could be a concern.
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In my area that set-up would never fly.
The return air duct should be attached to the return air intake on the unit.
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I agree, it’s new construction too. There are multiple defects with the installation. Again, what’s the model number? Then apply FBCR 1307.1, 1401.1, 1602.2 etc. Did you put a level on it? If the drain line gets clogged and the cut off switch fails, the house will flood.
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