Maybe easy HVAC question: net air loss from space

[cosmology]

Hey all. HVAC is not my area. I'm trying to find a way to air condition a shop space. I bought a portable A/C unit. I need something bigger, but that's not the point. With the portable, the thing exhausts a ton of air. It has a hose and you send the hot exhaust outside. So, my issue is that if my space is losing a ton of air, something has to0 come in to replace it. If the air outside is 100F, it doesn't seem like I'm doing a whole lot.

Split systems have solved. My question is do window units and through wall (hotel type) have net air loss from the space? I'm getting quotes on split systems, but if a through wall doesn't net loss a bunch of air, I might consider that route. Thanks

 

[John2025]

Are you sure it's exhausting room air? It should be using outside air to reject the heat.

 

[cosmology]

Yes, it one big exhaust hose. Many portable units are this way.

 

[lukaiENG]

A through-wall/window unit does not exchange air between inside and outside.
The indoor air passes over an evaporator coil and gets cooled down. The refrigerant circuit moves the heat to the condenser coil which rejects it to the outdoor air.
Thus, no air exchange - unless you seal around the edges badly.

 

[cosmology]

Thanks. I guess this feature is particular to portable units. It turns out there are some dual hose units that do not waste inside air. Much thanks!

 

[IRstuff]

The portable systems are simply less efficient, but count on being able to supply more cooling capacity than they are losing from the air. It works OK because the electrical power consumption provides the extra cooling capacity.

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[LittleInch]

The through wall units don't expel air but can bring fresh air in, up to 10% or so.

The split units are quieter but can't bring fresh air in and often need a separate drain line.

I had a single hose domestic unit and I generally got about a 6C reduction in temperature from ambient air temp and that was with my patented hose window insert which blocked the hot outside air returning. Instead it pulled in hot air from the rest of the house....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[cosmology]

Thanks. I found a technical guy on the phone with Freidreich who squared me away too. My space is a medium size warehouse (1200sf) in Texas (hot). Of the ones that can be DYI installed, he reccomended the SL-36, says it's built like a tank, often used as through wall. Considering it's 2k and a split system for the roof is going to be 5-8k, my choice is easy. If 3 ton isn't enough for the space (likely) I can add a second and be money ahead. Also, it's a rental, so if I move, I just roll it onto the truck and go. Thanks for the help.

 

[IRstuff]

I think there may be a couple of issues:
> The unit is a bit oversized for the area, so the unit might run short cooling cycles
> The air flow pattern will result in the immediate area being freezing (not literally) to the occupants, while the distal parts of the warehouse will still be warmish

You might want some ceiling or circulation fans to spread the air

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[cosmology]

Ceiling is 17'. 3 tons is probably not enough. Yes, the downside of no ducting will be using fans to distribute as needed. Worth the savings over here. Thanks all

 

[willard3]

You could hire an Engineer to help with this rather than trying to get free Engineering here.

 

[cosmology]

My question is a basic question about the functioning of the units. It's surprising to me how hard it is to find out very basic answers on things.. go to Lowes and ask any question of mild technical nature for example. I interned at an HVAC place (Siemens) but went a different direction after college (product design). I figured someone in the field my be here and know the answer easily. No need to be aggressive, but then what would the internet be without aggressive trolls.. yeah boring j/k Thread is over for me. Thanks for the helpful replies.

 

[IRstuff]

" With the portable, the thing exhausts a ton of air. "

Just to be precise, this is not correct. A "ton" refers to the effective cooling capacity of a mythical ton of ice. This is why the actual rating of your A/C is 36000 BTUh; note also, that the correct unit is BTU/hr, often simplified as BTUh. This now represents the amount of electrical or mechanical poewr the A/C needs to supply to continuously condense and expand the refrigerant to get the cooling you need. Luckily for us, the BTUh not 1:1 to electrical power. The SEER value is efficiency factor; an A/C might have SEER=12, so it would require roughly 3000 BTUh of electrical power.

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[cosmology]

In that sentence I was using "ton" figuratively not literally. Using figurative speech can be useful to get ones attention, kinda like dropping f-bombs, but less abrasive (figuratively again).

You say a 3 ton (btu type) A/C is over sized for 1200 SF, 17' ceiling, poor insulation, in Texas?

 

[IRstuff]

For a window A/C styled system, it might only be sufficient. There's always a trade against length of duty cycle and comfort.

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