A swamp cooler is an evaporative cooler: a fan pulling air through a soaked pad, which cools that air by evaporating water into it. It is the cheapest cooling a rental counter holds, roughly $50 to $250 a day by size, and it asks for two things a refrigerant machine does not, dry incoming air and somewhere for the air to leave.
These are rated in CFM, never in tons
Sizing is airflow against room volume, not cooling capacity. A small portable moves about 3,000 cubic feet a minute and suits a two car garage or a work bay. Trailer mounted units reach 20,000 and cover an open shed or a covered stage. Give the yard the room volume and how many doors will be open.
The door stays open or the machine stops working
Evaporative cooling adds moisture as it removes heat, so the air has to move through the space and out. Seal the room and the humidity climbs until the pad does nothing and everything feels clammy. Plan an inlet and an outlet: cooler at one end, open door or louvre at the other.
Water: a tank, a hose bib or a bulk delivery
Small units carry a tank that runs a few hours before somebody refills it. Anything working a full shift wants a hose connected to a float valve, so check there is a bib within reach of the parking spot. Hard water is the hidden cost, since scale shortens pad life and yards charge for a ruined pad.
When to spend the money on refrigerant instead
Humid coastal air, a sealed server room, or any space where a temperature has to be held rather than merely improved are all jobs an evaporative machine cannot do. Those are portable air conditioning hires with a condenser duct and a heavier power supply. Heat illness prevention also needs shade, water and rest, not one machine.
Questions people ask about swamp cooler rental
Does a swamp cooler work in humid weather?
Poorly. The drier the incoming air, the more heat evaporation can remove, so the same machine that transforms a dry summer afternoon in the southwest does very little on a muggy Gulf coast day. If the air is already close to saturated, hire refrigerant cooling.
Can I use one in a closed garage?
Not with the door shut. The cooler needs a path for the air to leave, otherwise moisture builds and the temperature stops falling. Leave the main door open a foot or run it with a side door and a roof vent open.
How much water does one use in a day?
A portable in dry heat can go through several gallons an hour, and a large trailer unit far more. That is the whole point of the machine, since the water is what does the cooling. Budget a hose connection rather than planning to carry buckets.
What power does it need?
Most portables run on a standard 115 volt outlet because they are only a fan and a small pump. That is the reason people hire them for temporary cooling where a spot cooler would need a dedicated circuit or a generator.