Air conditioners are engineered to be mounted in free air space...after all, removal of the heat is it's main purpose, and unfettered air flow is necessary for that to occur....Restrict the airflow and you create a potential hot air trap where the heat being exhausted is being sucked back through the condenser forming a thermal trap which elevates the head pressure, puts a strain on the unit, drops efficiency and performance, raises cooling costs and shortens the life of the equipment.... The most important thing is to have the charge set correctly, and the coils unrestricted...

I am thinking of a system with a separate hot air exhaust that would be to the outside.

Put it in the crawl space and return the rejected heat back to the living space to take it out again? Thats no way to make efficiency.

No.

No crawl space is ventilated to the degree of the airflow across that unit.

I have six vents and a large opening from the garage to ventilate it. The discharge would be to the outside, if that could be adapted.

you will NOT be able to properly vent the unit, we are talking LOTS of CFM of air to move. besides, crawlspaces are not typically insulated as well as you think, and all that heat will want to rise right back up into the house. in that situation you will most likely void the warranty to fare thee well.

Keep in mind that thermodynamics works on the Kelvin scale.

If your crawl space is 65 F and the air temperature on the side of your house is 80 F that might seem like the outside air is (80-65)/65 = 23 per cent warmer.

But in fact, your crawl space at 65 F is 291 Kelvin, and the outside air at 80 F is 300 Kelvin. So the difference is really only (300-291)/291 = 3 per cent.

So while the crawl space air might seem a lot cooler to you, thermodynamically the difference is not all that great.

not true, the outside condenser unit is typically sited to minimize the tubing run to the evaporator coil. if they CAN put it in the shade, they will, but the tubing run limitations dominate.

Thanks to everyone for their educational responses. I am finding out why a lot of things are the way they are.

Basement can be used to keep the chiller and it associated equipment. If it is a water cooled system cooling tower can be installed either at the roof or at ground level. AHUS can be located at any locations as per the site conditions and we have to ensure that it is available easily for service and fresh air opening.

There are numerous condensing units installed indoors in area's that are provided with make-up fresh air and exhausted tempered air. I have personally serviced and engineered many grocery store systems that have the condensing units in an equipment room or open well vented back room area. There is no reason why any condensing unit cannot be installed in a properly engineered indoor area.

You will have to pay for the power to handle the condenser air TWICE. Once with the condenser fan furnished with the unit and then the fan to exhasut the basement of the hot air off the condenser. You will need to exhaust about 500 cfm per ton of cooling cpacity plus providing adequate openings from the outside into the basement. Since you will pulling in outside air for the condenser it's going to be at outdoor temperature. Your crawl space will soopn be at the same temperature as the outdoors.

You'll be money ahead, both first cost and operating costs, to mount the unit outdoors in the shade. Tell the installing contactor you want the condenser coil protected from hail damage.

Lou Bindner