What causes this hot surface ignitor to fail

The "S" suffix indicates a built-in SPDT switch

System Protection: Actively monitors flue gas temperatures to trigger safety shutdowns before overheating occurs

a separate coil must be sourced

the A15099 is the current design standard specifically engineered to replace older metal-cap-and-gasket versions

Siemens Industrial Controls 3RK2200-0CQ20-0AA3 Module 320788-702 What causes this hot surfaceThe Siemens 3RK2200 0CQ20 0AA3 is a critical AS Interface digital I O module engineered for decentralized control in demanding HVACR and industrial automation environments. This IP67 rated I O module utilizes the compact K45 housing design, specifically optimized for field level installation without the need for additional enclosures. Featuring a 4 input configuration, the unit functions as an A B slave device, allowing for expanded addressing