Why Is a Rational Combi Oven Overheating and How to Fix It

Have you encountered a Rational combi oven that is overheating? This issue is quite common and typically arises from a defect in the solid state relay (SSR) that controls the current to the electric heating elements. In most cases, the SSR can short circuit and remain 'stuck on,' leading to continuous heating of the oven until the hILimit safety thermostat trips, removing power from the unit. This guide will provide a comprehensive explanation of the issue and offer a practical solution to ensure your oven operates safely and efficiently.

Understanding the Issue

When an SSR fails, it can no longer regulate the electrical current to the heating elements, resulting in them overheating and the oven reaching an unsafe temperature. A broken SSR can cause the heating elements to remain on indefinitely until the hILimit safety thermostat activates. This thermostat is designed to cut off power to the oven when the temperature exceeds a predefined limit. Unfortunately, this failsafe activates only after the SSR has already malfunctioned, leaving the heating elements in a constant state of overheat.

The Case of the Overheating Combi Oven

One of our clients purchased a Rational combi oven, but the equipment lacked proper protection. The hILimit safety thermostat only controlled the control input of the SSR devices, which is a significant oversight. When the high limit trips, the SSR is already in a 'ignore control signals and stay stuck on' mode, leading to continuous heating and, eventually, the activation of the safety thermostat. This means the oven can still overheat even after the high limit is triggered.

Consequences and Safety Concerns

Overheating ovens can pose serious risks, including damage to the oven, burnout of heating elements, and, more importantly, a fire hazard. If the overheating issue is not addressed promptly, it can lead to irreparable damage and even pose a danger to the operators. Therefore, it is crucial to identify and resolve the underlying issue as soon as possible. Ignoring this problem can result in equipment breakdowns and potentially dangerous situations.

Secure Fix: Adding Holding Contactors

To address this issue effectively, we recommend the addition of 'holding contactors' to the oven's power circuit. These devices can be configured to cut off power when the hILimit is activated, ensuring that the power to the heating elements is also disabled. This modification involves reconfiguring the hILimit to control not just the control signal to the SSR but also the power supply to the SSR itself.

Professional Assistance

Any individual with a background in electronics or electrical work can help solve this problem. However, for your safety and the safety of the equipment, it is highly recommended to seek assistance from an experienced electronics technician or electrician. Handling electrical issues without proper expertise can be extremely dangerous and may lead to injury or more severe equipment damage.

Prevention and Maintenance Tips

To prevent such issues from recurring, regular maintenance is essential. Ensure that the SSR and other critical components are checked and replaced as needed. Pay particular attention to the hILimit thermostat and ensure it is properly calibrated and functioning correctly. Regular cleaning and inspecting the oven’s electrical components can also help prevent overheating and ensure optimal performance.

Conclusion: Overheating in a Rational combi oven is a serious issue that can be traced back to a faulty solid state relay (SSR). By adding holding contactors and ensuring proper maintenance, operators can prevent such issues and maintain a safe and reliable cooking environment. Always seek professional help when dealing with electrical issues to avoid potential hazards.