Honeywell Control box ST7800A1039/U

The Honeywell Controller ST7800A1039/U is a plug-in purge timer module designed for use with Honeywell 7800 Series relay modules. It provides the prepurge timing function, with a prepurge timing of 30 seconds. This module is installed into the relay module compartment to control the prepurge cycle in burner systems.

Parts of this type are selected by matching the prepurge timing requirement and the relay module series. Installation involves disconnecting power, removing the keyboard display module, dust cover, data bus module, or remote reset module, and then pulling out the existing relay module if installed. The purge timer card must be aligned with the slot in the relay module and inserted properly. After reattaching the removed components, power is restored and the system is run through a complete cycle to verify operation.