Follow these 10 tips to increase the energy efficiency of your oven or dryer.

Click to enlarge

Put your oven into idle mode whenever there are pauses in production.

By selecting the most energy efficient options and features for your oven, you can reduce your energy use and operating costs considerably.

1. Look for Energy-Saving Mode

For an electric oven, consider a heating system that has an energy-saver mode. Functioning much like a clothes dryer in your home or overdrive for an automobile transmission, the energy-saver mode allows you to run your oven using less electricity for everyday use while still having more power available when needed. Using a selector switch or PLC input, the heater circuits are only partially energized during energy-saver mode. This decreases your peak demand charge and can provide savings on your energy bill.

2. Minimize Your Exhaust Rate

In most industrial ovens, an exhaust fan is required to remove solvent vapors, moisture or combustion byproducts. Exhaust fans allow adjustment of the volume of air removed from the oven using either a manual damper or variable-frequency drive.

It is critical that your exhaust fan be adjusted to the minimum setting necessary for the process. Too often, exhaust fans are not adjusted properly, wasting large amounts of energy and money.

3. Add a Heat Recovery System

Oven exhaust air carries a great deal of heat energy. A heat recovery system may be able to recover heat from exhaust air and return it to the oven. A plate- or tube-style heat exchanger is used to transfer heat from the hot exhaust air to the incoming factory air. Payback periods are commonly one to five years, and rebates often are available from local utilities to offset the initial investment.

Click to enlarge

An oven with an energy-saver mode decreases your peak demand charge and can provide savings on your energy bill.

4. Consider Humidity Control

When drying very wet product, consider adding a humidity control system to vary the exhaust rate of your oven or dryer.

A humidity control system continuously senses the humidity level in the oven and uses closed-loop control to reduce the oven exhaust rate to the minimum necessary to achieve the desired product dryness. The systems are especially valuable in dryers that process many different materials with varying moisture levels or with intermittent loading.

5. Monitor Lower Explosive Limit (LEL)

Also commonly known as a solvent monitor, the LEL monitor senses the concentration of flammable solvent vapors inside the oven and sounds an alarm before it reaches a dangerous level. National Fire Protection Agency (NFPA) code allows oven exhaust volume to be reduced by approximately 50 percent if you use an LEL monitor, which can reduce your dryer’s energy use and operating cost dramatically.

An additional advantage is safety: the LEL monitor will shut off the oven heat source if the vapor concentration becomes too high, preventing fire or explosion.

Click to enlarge

High temperature curtains such as those shown, powered air seals or unheated vestibules should be used to retain the heat.

6. Install Thicker Insulation

A portion of the heat generated inside an oven is continuously lost through the insulated walls. This lost heat consumes energy. By using thicker insulation, this loss can be reduced and your oven will operate more efficiently.

When purchasing a new oven, specifying just an additional 2" of insulation can save thousands of dollars in energy costs over the life of the equipment. The good news is that the cost of this feature is very reasonable.

If you have an older existing oven, it can benefit from additional insulation as well. It is common for older ovens to have areas where the insulation has settled or broken down. This is indicated by hot areas on the oven exterior. These areas should be repaired to maintain the oven’s efficiency.

7. Properly Seal Oven Openings

For conveyor ovens, it is critical to properly seal the area where the conveyor and parts enter and exit the heating chamber. High temperature curtains, powered air seals or unheated vestibules should be used to retain the heat. Even a small leak wastes significant energy.

On batch ovens, be sure door gaskets are in good condition and seal tightly.

Click to enlarge

A heat recovery system uses a heat exchanger to recover heat from exhaust air and return it to the oven.

8. Add a Variable-Speed Recirculation Fan

Heated air becomes lighter, so an oven’s recirculation fan does not have to work as hard after the oven reaches temperature. A variable-frequency drive can be used to power the recirculation fan and ramp up its speed (rpm) while the oven heats up, matching the motor horsepower with the fan requirements. In this way, the motor can operate at its optimum horsepower rating and achieve maximum efficiency. As the price of variable-frequency drives has dropped in recent years, this feature has become more attractive.

9. Use the Idle Mode

Put your oven into idle mode whenever there are pauses in production for tooling changes or operator rest breaks. During idle mode, the oven temperature is temporarily reduced to a preset temperature, so it uses less energy. Ask for this feature when purchasing a new oven, or consider adding it to an existing unit. To avoid accidentally restarting production while in idle mode, use a flashing light or beacon to signify when the oven is idling.

However, do not use idle mode for long periods such as overnight. You will save more energy by shutting the oven off and restarting it eight hours later.

10. Properly Maintain Your Equipment

Maintaining your oven equipment properly cannot be overemphasized. Properly maintaining it - or failing to maintain it - will significantly impact your energy costs.

To increase efficiency, maintenance programs should ensure the burner is adjusted properly, filters are kept clean and recirculation and combustion blowers are properly maintained. Your oven does not have to be an energy hog. Follow these steps and “go green” for both for the environment and your pocketbook. PH