How to Use Evaporative Cooling Properly

The one idea behind everything

An evaporative cooler is not a refrigerated air conditioner. It does not chill a sealed house. It pulls outside air through wet pads, cools it as the water evaporates, and pushes that cooler, slightly damper air through the ducts into the rooms. For it to work, that air has to keep moving through the house and out again. Every rule below comes from that one fact: the air needs a way in and a way out.

Turn it on early

The most common mistake we see is switching the cooler on when the house is already hot. By then the walls, the floor and the furniture have soaked up the heat, and the cooler is trying to cool the air and the building at the same time.

Turn it on early in the day, before the house heats up, and run it steadily. On a hot day the cooler’s job is to stop the house getting hot, not to rescue it once it is.

Give the air one deliberate path

Opening every window and door does not help. It creates competing drafts, and the cool air escapes through the nearest opening instead of travelling through the rooms you are in.

The idea is to make one sensible airflow path:

• Open the internal doors to the rooms that have evaporative outlets.
• Where practical, close off rooms without outlets, so the cool air is not wasted on them.
• Choose a suitable external opening for the air to leave through, on the far side of the rooms you want cooled, so the supplied air moves through the occupied areas and escapes.
• Open that outlet enough to let the air out, not so wide that the whole house becomes a wind tunnel.

You will hear advice about which side of the house to open. Wind direction and site conditions differ from home to home and day to day, so the useful principle is this: prefer an opening on the leeward side of the house rather than one that opens straight into a hot prevailing wind pushing back against the cooler. If the air at the outlet feels like it is being pushed back in, choose a different opening.

Fan mode and cooling mode

On most days you want cooling mode, with water running over the pads. On very humid days the air is already carrying a lot of moisture and evaporation slows, so cooling mode gives less relief and the house can feel clammy. On those days fan-only mode, which simply moves air through the house, can be more comfortable. Try it rather than assuming the cooler has failed.

What “not cooling” usually means

Before you decide the cooler is faulty, check the basics:

• Is there an airflow path out of the house, or is everything shut?
• Was it turned on early, or is it fighting an already hot house?
• Is it a humid day?
• Are the pads wet across the whole face (you can often see this at the outlets by the feel of the air)?

If the air is moving strongly but is not cool, the water side is the usual suspect: the pump, the float, the water supply or dry sections of pad. If there is little airflow, it is more often the fan, the controller or a blocked pad. Those are technician jobs. Do not climb onto the roof or open the unit.

Humid days, storms and smells

A musty smell on the first hot day is almost always stale water and build-up on the pads after months of sitting. A proper clean of the tank and pads deals with the cause. It is also why a spring service, before the first heat, is worth far more than a call-out during it.

The common mistakes, in one list

1. Turning the cooler on too late.
2. Opening too many windows and doors.
3. Opening the wrong side of the house into a hot wind.
4. Leaving the rooms with outlets shut and the rooms without outlets open.
5. Expecting refrigerated-air behaviour on a humid day.
6. Running cooling mode on very humid days instead of fan-only.
7. Skipping the yearly service and then discovering the pump or the pads have failed in January.

When servicing, repair or replacement is the answer

A yearly service keeps the pads clean, the water system checked and the airflow tested; our evaporative cooling service page shows what that involves, with real footage. Faults with the pump, float, fan, controller or water lines are repairs, and most are sensible to fix. When a unit is old, the cabinet is cracked, parts are no longer available or the repair no longer makes economic sense, we will say so and explain the replacement options, with Brivis as our preferred brand.

If you are converting the home to electric heating and cooling, see whether to keep the evaporative cooler.