Right size your Heater: Don’t just buy the Biggest or Cheapest

Or – Why heaters come in different sizes

Every application requiring hot air has its own design requirements. Ideally, these requirements will guide the designer to the right heater for the job. Unfortunately, many times design decisions are made based on price or with a “bigger is better” mentality.

Looking at Leister’s line of air heaters you may notice that while the heaters range in power from 550W to 16kW they all have a maximum operating temperature of 650°C. We’ve written previously about the difference between temperature and heat and why the power rating of the heater is the critical specification when sizing a heater.

The following are a few of the questions a designer should answer when choosing a heater:

1. How many kW do I actually need?
   ​It’s important not to undersize or oversize the heater. If the heater is undersized it will not have enough power available to perform the task required. In order to reach the required temperature it may be necessary to reduce air flow to a point where either the amount of hot air is not enough to perform useful work or damage to the heater is possible. Temperature is also much harder to control when air flow is limited. If the heater is greatly oversized it may require more current than is available on your circuit and it may result in higher power bills (which are often charged based on peak load). You may also reduce the control sensitivity if the heater is always working in the very low range of its capability. Read our article on for help sizing your heater correctly.
   ​
2. Do I have geometric or spatial constraints?
   There are numerous reasons why the physical size of the heater could be limited. Neighbouring equipment could limit total size or orientation. Integration into a machine often forces the heater to be as small as possible. The application may require the barrel of the heater to be larger than available on a tool with the correct power rating. In any of these cases you may have to choose a heater with a suboptimal power rating to accommodate these constraints.
   
   
3. How much air flow do I need?
   Using hot air is not only about temperature but also about air flow. The required air flow for an application directly impacts the required power rating of the heater. For example, if a large volume chamber needs to be filled with hot air you will likely need a higher powered heater than if you are spot heating a small area of a part. Larger air flows, when the target temperature is held constant, necessitate higher powered heaters.

Choosing the right heater for your application is a multidimensional problem. Many times designers don’t give enough thought to the right heater for their application and default to simple criteria like size or price. This will ultimately lead to bad equipment decisions. If you would like expert advice on choosing the right heater for your application please give STANMECH a call.