Wet Cardboard Stinks. Get a Can Warmer.
- 6 days ago
- 5 min read
Updated: 6 days ago
By Dan Welch, CODI Manufacturing
What is a Can Warmer and why would I need one?
Cold beverages and cardboard packaging do not get along. The paradox is this: liquids retain CO₂ better at low temperatures, so carbonated beverages are filled cold and stay cold through the packaging process. The problem starts the moment those cans hit ambient air. The cold can surface sits below the dew point, condensation forms, and then the wet cans will weaken and warp any cardboard tray or carton they touch. The fix is either waiting hours for the cans to warm up naturally, or a can warmer that does the same job without wasting your time.
How Can Warmers Work
To understand a how a can warmer operates, it helps to think of it like this: the cans are along for the ride, and the water is the one doing the work.
The can’s journey is straightforward. Cold cans move into the tunnel on the conveyor, take a hot shower from above and along the sides. The heat from the sprayed water transfers through the aluminum and into the product inside. Cans exit the warmer roughly 20°F warmer than when they entered, above the dew point, and that is all it takes to keep the packaging dry.
But the water’s journey is where the story is.
It starts when the hot sprayed water hits the cold cans. On contact, the sprayed water transfers that heat immediately to the cans, dropping 10–20°F in the process. That cooler water then drains off the cans and falls into the basin below, where it’s captured and recirculated, not wasted.
From the basin, the loop begins again. Most of the water heads back toward the spray headers, but a controlled portion is peeled off and sent through a heat source. That side stream gets brought back up to the target temperature, then blended back into the basin so the whole system stays in balance. Two temperature sensors act like the traffic cops in the loop, constantly adjusting how much water takes the reheat route to keep the spray temperature steady through the entire run.
It’s Getting Hot In Here
Before we talk about how to heat the water in a warmer, let’s take a quick detour to talk about thermodynamics (don't worry, I was a music major, so we are not going too deep here, I promise).
Warming a filled can requires energy, delivered as heat. How much heat your process needs depends on three things:
how much liquid is in each can
how many degrees you want to raise it
how many cans you’re pushing through per minute.
In the U.S., we usually talk about that heat requirement in BTUs. So if you want to know whether a warmer is sized correctly, you start by estimating the BTU-per-hour load required to hit your target temperature rise at your actual line rate.
Here’s the key point: you’re heating the liquid in the container, not just container itself. Liquids such as water and beer take a lot of energy to change temperature, which is why a “small” temperature bump can still require serious heating capacity. Hot water droplets hit the can, heat passes through the can wall, and the product inside warms up. A droplet spray pattern that wets the surface consistently increases contact and speeds up the transfer.
Now think about the cans traveling through the tunnel. As cans per minute [CPM] goes up, more cold product mass enters the tunnel every minute. That pulls more heat out of the spray water, which means the heater has to replace that energy fast enough to hold the spray setpoint steady. Higher CPM equals higher BTU demand, and that drives both the heating approach and how many heating units you need.
For a rough reference point, common commercial instant hot water heaters used in warmer applications are often rated around 199,000 BTU/hr each. A medium-sized can warmer might need two or three. The sizing logic comes back to the BTUs that are required to keep up with the mass flow on the conveyor.
[NOTE: Although CODI is known for our Tunnel Pasteurizers, a warmer is not a pasteurizer. Pasteurization units accumulate only when the product crosses the 140 to 160 degree Fahrenheit threshold. A warmer operates well below that range and requires no PU calculations. The objective is temperature equalization, not microbial reduction.]
Heating Methods
CODI warmers support two heating configurations: instant hot water heaters and heat exchangers. Both achieve the same result and share the same system architecture. The choice depends on the utilities available at the facility.
Instant hot water heaters are the more common configuration for facilities without existing steam infrastructure. Commercial units rated at 199,000 BTUs each can be stacked to meet the required heating load. CODI specifies the number of units for the application and provides the connection point. If our customers prefer to source and install the heaters independently, CODI will work to any connection specification.
Heat exchangers are the preferred configuration for facilities with steam. The heat exchanger mounts to the top of the machine at the same position used in the instant hot water heater configuration. Return water from the recirculation loop passes through one side of the exchanger while steam runs through the other. The steam raises the water temperature back to the target spray temperature and it returns to the spray headers. The steam condensate is recovered and returned to the boiler through a condensate pump, retaining residual thermal energy in the loop.
A recent Can Warmer build with instant hot water heaters
Sizing and Speed
CODI warmer models are designated by the treatment area. The smaller Can Warmer, CMT-10, has a 10 square foot treatment area, configured as a 2’ by 5’ belt. While our larger Can Warmer, CMT-25, has a 25 square foot treatment area on a 5’ by 5’ belt.
The CMT-10 produces roughly 100 cans of instantaneous coverage in any given linear foot of the machine. So at a belt speed of 1 foot per minute, output is approximately 100 cans per minute. At 2 feet per minute, output doubles to 200 cans per minute. For sizing a good rule of thumb is a can density of about 21 cans per square foot for standard formats.
Speed and spray temperature are the two variables a warmer operator controls. Running the belt faster reduces dwell time under the spray, which reduces heat transfer per can. To compensate, spray temperature must increase. A 200 CPM run on a CMT-10 may require a spray temperature of 150 degrees Fahrenheit. That is achievable with appropriately sized heating capacity, but it must be specified correctly upfront.
CODI Can Help
Defining the problem of why a can warmer is needed is simple: to eliminate excessive condensation moisture prior to secondary packaging. The science behind it, however, is more challenging to explain. No worries, CODI can assist you by providing throughput calculations for each warmer configuration when you are evaluating your decision. Those calculations include entry temperature, target exit temperature, belt speed, spray temperature, and required BTU load.
We can make it easy: Tell us your line rate and your temperatures. We will handle the math from there.
About CODI Manufacturing
CODI Manufacturing has been designing and building packaging automation in Colorado since 1992. We offer a complete line of beverage packaging equipment including can warmers, built in the USA and engineered to last. Veteran-owned. Machinery and a business that are "Built for Generations."
About Dan Welch
Dan Welch is Growth & Marketing Strategist at CODI Manufacturing. He spent over two decades as a sales and marketing executive at a Fortune 500 company before pivoting to the craft beverage equipment industry in 2018, where he held senior sales and general management roles. He joined CODI in 2025 and is based in Colorado.
Comments