ONAN vs KNAN Cooling in Pad Mount Transformers (3/18/2024)

KNAN transformers use natural esters or synthetic fluids with significantly higher flash points.

Article - March 18, 2024 By LarsonElectronics.com

1 MVA Pad Mount Transformer - 13200V Delta Primary, 480Y/277 Wye Secondary - ONAN/Bell Green

ONAN vs KNAN Pad Mount Transformer

Pad-mounted transformers come in different types of cooling classes. Two common configurations include Mineral, Oil Natural Air Natural (ONAN) and Non-mineral, Oil Natural Air Natural (KNAN).

The crucial difference lies in the oil type and internal cooling features.

ONAN Transformers

ONAN transformers utilize traditional mineral oil, which is less expensive but has a lower flash point, making them more susceptible to fire. This limits their use in high-risk environments.

The external cooling mechanism of this type of transformer is air and natural convection (A and N). In some cases, a transformer can have extended cooling class ratings for additional loading capacity, such as ONAN/ONAF. This transformer uses forced air for cooling at a specific threshold.

KNAN Transformers

KNAN transformers use natural esters or synthetic fluids with significantly higher flash points. These coolants offer superior fire safety, making KNAN transformers the preferred choice for hazardous locations where explosive atmospheres pose a risk.

The external cooling mechanism of this type of transformer is air and natural convection (A and N). A KNAF transformer utilizes forced air external cooling mechanism (F).

Which One Should You Use?

While both methods rely on natural air convection for external cooling, some transformers might have extended ratings with forced air cooling for handling higher loads. Additionally, KNAN coolants features biodegradability and better moisture tolerance compared to mineral oil, making them a more environmentally friendly option.

ONAN is the traditional and cost-effective choice for standard applications. If you’re looking for a tried and tested transformer solution for conventional installations, it makes sense to use an ONAN transformer. On the other hand, KNAN cooling offers a safer and more sustainable alternative for situations demanding fire safety and environmental responsibility. If your project has specific environmental or sustainability requirements, consider using a KNAN transformer for your installation.