Can a swamp cooler catch on fire? What happens when they run out of water?
Quick answer: A swamp cooler will not catch fire, even when the water runs out. Swamp coolers run on low wattages, which makes overheating highly unlikely. Swap coolers are the safest cooling devices (together with fans).
Do swamp coolers overheat when they run out of water?
A swamp cooler is a fan that blows air through wet sponge.
When your swamp cooler runs out of water, it blows air through the dry sponge.
One common cause of fire is the accumulation of heat energy in a small space. However, there is always airflow in a swamp cooler. The fan still blows air when the water runs out.
So, a swamp cooler does not accumulate heat. It dissipates the heat into the room.
A swamp cooler without water is still a fan. Fans don’t catch fire because they distribute hot air.
Can swamp coolers overheat due to electronic failure
Of course, a swamp cooler can overheat when there is a fault in the electronic circuitry. But this is never due to the swamp cooler running out of water.
If a swamp cooler has an electronic fault, it can catch fire even when the water supply is still active.
This can happen to any electric device. And swamp coolers consume such little power, I’d claim running a fridge or a TV is more dangerous.
Overheating due to electronic failure is very unlikely. Because most swamp coolers run on low power, overheating can only happen when the electronic components that sit inside the swamp cooler are too cheap or don’t suit the use case.
As long as you have a decent-quality swamp cooler, it is very unlikely that the electronics will ever overheat.
I recommended my all-time favorite sturdy swamp coolers in this recommended swamp cooler article (it’s about swamp coolers in garages, but these are precisely the best quality swamp coolers with the best airflow).
Swamp cooler overheat risk by size
The maximum temperature of a device depends (among a few other factors) on the power it consumes.
Swamp coolers are low-power devices. Naturally, they don’t run hot. None of the temperatures in the table below is high enough to start a fire.
|Swamp cooler size
|Maximum component temperature
|Is it hot enough to catch fire?
|250 Watts (big)
|100 Watts (regular)
|50 Watts (small)
As you can see, even large swamp coolers are fire safe. Usually, the fan motor warms up while running, until it reaches its maximum temperature.
But still, there’s nothing to worry about.
How I got these numbers (skip if you don’t like maths)
For the temperature estimation, I use the following assumption:
No motor is 100% efficient. A swamp cooler fan motor dissipates 10% of the energy as heat.
Based on this assumption, I can estimate the maximum temperature of the internal components, e.g. the motor and the electronics.
At home, I have a 7 Watts heating pad for reference.
For example, the small 50W swamp cooler will generate 5W of heating power. My 7W heating pad gets about 90°F hot. If 0W corresponds to a room temperature of 77°F, that means 5W should be around 85°F.
Please note that temperature does not rise linearly with power. So, I am estimating logarithmically.
In which case can a swamp cooler catch a fire?
Swamp coolers only ever catch fire due to electronic or mechanical failure. A normal-running swamp cooler will not catch fire on its own.
Which parts in a swamp cooler can catch fire?
1. Built-in fan
The built-in fan itself is unlikely to catch fire. But it can cause a fire in the electronics if it stops moving.
This can happen when something blocks the rotational movement of the fan. For example, when a broken part blocks the fan, or when the fan bearings break.
Then, the fan does not absorb the power the power electronics deliver to it. The input power, however, has to go somewhere.
And usually, this leads to a single electronic part or a wire to overheat or blow up.
This scenario is very unlikely. A swamp cooler fan does not simply block itself from moving. And normally, bearings also don’t break down.
The only fan-blocking scenario I can think of is a wasp nest inside your swamp cooler.
To prevent this, you can get a swamp cooler cover (click here to view one on amazon).
2. Power cord
Most power cords can easily handle the power of a swamp cooler. AC power cords, for example, have to withstand at least 3x the amount of power of a swamp cooler.
And you rarely hear about ACs that cause fires.
Swamp coolers need 2.4 Amps at most. Even some phone chargers can deliver >2.0 Amps.
So, it’s really not that much.
The only way a swamp cooler power cord can catch fire is if is either
- broken (through dog or cats nagging on it or loose contact from heavy usage)
- loosely connected to the wall outlet
- loosely connected to the swamp cooler
But as long as you firmly connect the power cord and it does not have any visible faults, it won’t cause a fire.
I’ve written an article on how to fix a swamp cooler power cord here.
3. Power electronics inside the swamp cooler
Another point of failure is the power electronics driving the fan inside the swamp cooler.
The power electronics component receives the input power from your wall outlet, converts it, and forwards it to the fan, depending on the airspeed setting you set.
Especially cheap devices often have bad-quality power electronics, with parts that barely suit the voltage requirements.
If this is the case, things can stop working or even blow up in the electronics.
But it is still very unlikely that any part catches fire.
I’ve worked in an electronics manufacturing plant once. And the only time I saw an electronic circuit board catching fire was when there was a short circuit. So, it has to be a major quality issue for something to go wrong.
If your swamp cooler had a short circuit, it would never even turn on. So, if you ever see your swamp cooler working, there is no short circuit and nothing to worry about.
( Of course, things falling onto the circuitry or water droplets can cause short circuits too. But generally, the power electronics are separate from any moving parts and separate from the water. )
4. Extension cord
For air conditioners, you need high-quality extension cords. But swamp coolers use such little power that even cheap extension cords suffice.
As long as you tightly connect the extension cord with your swamp cooler’s power cord and the wall outlet, you are safe.
Swamp coolers don’t catch fire, even if they run out of water. There is just no component inside a swamp cooler that receives enough electric power to start a fire.
On top of that, swamp coolers distribute air. So, they would blow away all the heat that accumulates inside.
Swamp coolers are very safe devices. They are much safer than regular ACs, which run on very high power, and almost, but not quite as fire-proof as a regular fan.
The only difference between a swamp cooler and a fan is the casing and the electronic circuitry.
So, there is more material to catch fire.
But in principle, both swamp coolers and regular fans, are fans. Fans don’t catch fire.