Steel Boilers & Water Heaters. The Aldrich Company is locally owned and manufactures a wide variety of hydronic heating equipment. Most notable are their indirect fired water heaters and primary/secondary modular boiler systems. The indirect heaters are known world wide for their longevity and ease of maintenance. Their newest introduction of primary/secondary modular boiler systems is fast becoming the model for efficient hydronic space heating. This is accomplished by an innovative multiple vessel concept run by a computerized control technique.