So, super important to note that this is strictly prohibited and dangerous with a gas furnace, or if there are gas appliances in the same area. You will go to sleep and not wake up.

I'm sure it's prohibited even if it's not gas, just because you can't predict what will happen in the future -- Someone installs a gas water heater or leaves the door open but closes a different door and suddenly sucking CO into the space.

And where is the filter rack in all of this?

Look for a sticker from the installer. I'd call them and tell them to fix it - even if it was 20 years and a few owners ago.

This is electric, in a condo building that has no gas lines. I am confident in saying there will never be gas in this unit (there is none in the neighborhood). That said, thank you for the response and thinking of something I hadn't thought of.

The filter rack is on the bottom of the fan coil unit, where the bottom green circle is. It is why the pipes have such a funky shape there, to get the filter in and out. I did look for a sticker, couldn't find one on anything HVAC here, I'll check again.

I'm sure there are plenty of reasons this isn't done in general, and could be a bad idea. You are certainly extending my list. I do wonder if this room wasn't designed for this purpose, though. It is sealed to the outside, though it could pull air from between walls, I suppose. The easier paths are that return duct and under the door. No other plumbing is in this location aside from the drain for the unit itself. If I could get it altered quickly and for not too much expense I probably would at this point.

I'd still be interested to hear from anyone else who has ever seen anything like this. Perhaps it is just bad design or something that was OK 40 years ago when the condo was built.

Because it's a condo, the outdoor unit (condenser) maybe chilled water that serves the entire condo, then there are branch circuits that feed the individual condos.

It's often called 'Chilled Water Loop'. But I don't see any chilled water pipes the picture isn't clear enough, it's a guess that the box directly below the air handler may contain this and the pipes are out of view.

The box below the air handler may also be a transformer so without a clear picture this is merely an elaborate guess.

Austin Air Companie

I've worked with chilled loop setups and that's pretty clearly a refrigerant line set, not cold water loop.

I don't know what that box is on the floor, but it looks like it has a yellow DOE energy sticker on it.

Regardless, the setup is bogus for the reasons that I've already listed. It doesn't mean that the owner needs to run out and get it fixed now... but it's not something that should have ever happened.

yeah it's true it looks like refrigerant line set, but when it comes to condo's you just never know. The unidentified box may be a branch circuit of some kind that distributes the refrigerant?

These kinds of setup's can be quite special and without a clear picture of both indoor and outdoor equipment we can only speculate.

I don't work on chilled loops that is a specialty market with not enough equipment to remain employed for long (IMO), and clearly they look different than this setup... this could be some newer fandangled method somewhat similar to a chilled loop system?

The chilled loops I've seen were much older systems.

"Chilled loops"............ Is that what we used to call "swamp coolers"?

"swamp cooler"
No, they circulate cold water through a central cooler rather than each unit having their own condenser. The chilled water goes to an air handler.

Chilled loop systems don't use small insulated tubing. It's all insulated and it's all 1/2" or better.

Nonetheless, you don't do the return ducting that way.

no not a swamp cooler.

After thinking about this further my further educated guess is water chilled condenser.

Basically how this works is water is used from a cooling tower to cool the refrigerant, that is piped into the big box below the air handler. The big box is where the compressor sits. I've attached a picture that shows basic configuration of how this works.

The return is likely attached to a fresh air economizer. I am going out on a limb when I say that as we don't know the location of this 'condo'.

Why would they do this? space is a premium in a condo. The more units they can cram into that space the more condos they can sell. It's far more cost effective 'space wise' to have one 'water cooled' condenser that serves the whole condo complex.

The condo dues cover the cost of the water cooled condenser. If you have a problem with your unit, the unit is accessible thru your own condo. This can limit theft problems, or contractors stumbling onto the wrong unit and damaging something among many other out comes.

PS: it could also be geothermal ground loop. Like if there is a pond or lake on the premises.

Hey guys, if you were still curious, the unidentified box on the bottom of the photo is the heat pump. It pulls air in and spits it back out from outside the building right there.

Decided to set up a maintenance inspection for the system, get things in order and see what they think about adding ducting to the system.

Is there a cooling tower on the property or pond? Not that it matters just curious. I doubt they would put in a ground loop as typically space is a commodity in a condo. But dual feature like a pond with fountains, I could see that.

The cooling tower if hidden well wouldn't be too bad, but I think for higher end looks the pond might be more likely. Plus, the cooling tower would be more expensive long term due to water usage.

heat pump just means the unit has the ability to provide heat in the winter by reversing refrigerant flow. Your auxiliary heat would be electrical resistance strips.

Is the condo in Florida by chance?

Condo is in Virginia, and each unit's HVAC is entirely independent. No ponds or cooling towers. The condenser is just that little box below. I always thought it was a handy, if odd, little setup for a small condo space.

If folks are still looking at this thread, I was wondering if I could invite comment on the drain/ p-trap. Jake was happy to provide opinion on the ducting and why it should probably be corrected. I don't want to take silence on the drain/ p-trap as approval, but I'm curious to see what ya'll think. I was pointed to the EZ Trap and advised to have an HVAC contractor put one in. Wanted to get some thoughts before he comes by end of week.

I recommend installing an EZ Trap with an overflow switch. The switch will shut down the AC in case there is a back up of condensate. I like the clear trap so you can see if there is any debris. Your current set up has a trap, but you have no way of cleaning it out if it were to become clogged.

No ponds or cooling towers. The condenser is just that little box below.

It has to be ground loop geothermal system then, or some odd remote condenser set up on the roof somewhere?

Because that box below the AH has no condenser coil or fan, it must use some other means of cooling the refrigerant / removing heat from structure and heat of compression of the refrigerant cycle.

Unless the condenser is protruding thru that brick wall and the condenser is a side discharge model, but given the way this box looks I doubt it.

Drain P-trap.

I would leave the existing P-trap as is. There should be another threaded condensate connection directly to the left of the primary drain connection you have. Remove the plug and pipe this to a pan on the floor with a float switch.

Putting an inline switch in the primary condensate often times leads to short cycling as the drains often don't clog all at once. Too much short cycling and you have the opportunity of killing your ac compressor.

Until you know what’s what, it’d probably be a good idea to remove those cleaning products from the door shelving.