Simoneau economizers are designed with finned or bare tubes.
Bare tube economizers feature an inlet header and an outlet header, connected by a bundle of bare tubes.
Finned tube economizers share the construction of bare economizers. However, the tube fins are exposed to the hot flue gases, increasing the heating surface per linear foot of tubes and resulting in a more compact unit. Finned tube economizers can be condensing and built with stainless steel tubes and components.