When there’s nowhere to install an air conditioner, when an air conditioner or HVAC system fails, or when air conditioning would be too expensive, a spot cooler is a fast, easy, portable solution that can meet your cooling needs over the short or long term.

What is a spot cooler?

Spot coolers, also called spot air conditioners or spot cooling AC units, are self-contained portable cooling units that deliver targeted cooling to rooms, equipment or people. Most units roll on casters and plug into a wall outlet, so you can place them where you need them.

How does a spot cooler work?

Spot coolers work much like air conditioners. In an air-cooled spot cooler, air is drawn into the unit and across two sets of coils, first the condenser and then the evaporator.

In the condenser, the gas refrigerant, which has been pressurized by the compressor, is turned into a warm liquid. Some of the heat exits through vents in the unit; a duct is usually installed to carry it out through a window, door or ceiling panel. Warm air then passes into the evaporator, which cools the air and removes moisture. The cool, dehumidified air is pumped back into the room through nozzles, which direct the air where you want it to go.

The cooling process creates condensation. That water drains into a bucket, which in some units must be emptied manually. Alternatively, the water can be captured by a drainage hose and directed into a drain or outdoors.

Types of spot coolers

There are several types of spot coolers, including air-cooled models, heat pump models and water-cooled models.

Air-cooled spot coolers

Air-cooled units are the most common type of spot cooler. In air-cooled units, the warm condenser air is vented through a duct.

Heat pump spot coolers

Heat pump spot coolers are similar to air-cooled spot coolers, but in addition to working as an air conditioner, they can also work as a heater. They must be hardwired by a qualified technician.

Water-cooled spot coolers

Water-cooled spot coolers use a water source instead of a condenser to remove hot air. That means there’s no condenser air discharge. Water-cooled units work well when there’s no good way to duct out waste heat.

Common uses for spot coolers

Spot cooling units have countless applications.

Robust cooling on short notice: Spot coolers provide temporary cooling when an HVAC system fails or underperforms. When businesses with critical cooling requirements, such as food suppliers and pharmacies, need robust emergency cooling on short notice, spot coolers fit the bill. They can be used to augment existing cooling systems in healthcare settings and retail settings during a heat wave.

Special events: Spot coolers can be deployed during special events in venues that have no cooling or have insufficient cooling.

Data centers and server rooms: Spot coolers can be an excellent choice for server rooms and data centers because cool, dehumidified air can be routed directly to the equipment.

Production floors: Spot coolers are ideal for targeting specific areas within a much larger space. For example, it’s impractical to cool a million-square-foot production facility, but cooling a production line where the workers are standing makes sense.

Tall buildings: When a large portable air conditioner would require too much ducting, a spot coolers are the logical choice. For instance, running ductwork to cool one floor of a tall office building would be labor-intensive, but spot coolers can be positioned where they are needed. An added benefit: When cooling needs change or a workspace moves, you can easily relocate the spot cooler.

Spot cooler sizing: What size do you need?

Spot cooling AC units remove anywhere from 1 ton to 5 tons of heat per hour depending on the size of the unit.

Spot coolers are sized by tonnage or Btu. A ton describes how much heat a unit can remove in one hour. Heat is measured in British thermal units (Btu), and a ton is the equivalent of about 12,000 Btu.

A 1-ton unit can cool a 400 square-foot space, a 2-ton spot cooler can cool about 800 square feet and 5-ton unit can cool about 2,000 square feet. Variables other than square footage will affect the Btu needs. They include the ceiling height, the number of windows, the degree of insulation, the outside temperature and humidity and the number of people or computers in the space.

In certain situations, it’s smarter to go by cubic feet instead of by square footage. One example is a warehouse stocked with temperature-sensitive items stored on elevated racks.

It’s important to size your spot cooler correctly. If it’s too small for the space, it may never shut off, causing the evaporator coil to freeze up. The same thing can happen if you set the thermostat too low.

Spot cooler installation

Smaller units that use a standard outlet are typically simple to install. Installation of higher-voltage units requires an electrician.

Ease of installation depends on several factors, including room placement, where the hot air duct will be vented and how the condensation water will be managed. Contact an expert to avoid problems with ductwork, drainage and airflow.

Dave Johnson is a Los Angeles-based freelance writer who has been writing about all aspects of business and technology since before there was an internet.

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