Industrial A-5503 Pneumatic Temperature Switch

The Armstrong A-5503 Pneumatic Temperature Switch is a dedicated pneumatic control device from Armstrong Machine Works, identified by manufacturer part number A-5503 and described in distributor listings as a “PNEUMATIC TEMPERATURE SWITCH FOR STEAM HUMIDIFIERS” for steam humidifier applications. This OEM Armstrong component is listed by IMS Supply with Manufacturer Part Number A-5503 and packaging described as sold individually, and it appears in Radwell catalogs as the A-5503 model, noting its use as a pneumatic temperature switch for steam humidifiers and its status as discontinued by the manufacturer. The unit weighs approximately 0.28 lb, reflecting its compact, field-replaceable design typical of Armstrong humidifier controls. Across multiple catalogs, the A-5503 is consistently associated with steam humidifier systems, confirming its intended role as a replacement control element within Armstrong’s pneumatic humidity-management offerings, even as availability may be limited due to its discontinued status.