This controller provides ignition sequence, flame monitoring, and safety shutoff for intermittent pilot central furnaces, residential boilers, and other heating appliances

This control module is NOT designed to replace controls in applications with: Flame Sensing other than by flame rectification, standing pilot appliances, direct main burner ignition

On this model, unlike previous Honeywell S86XXXX models, the transformer secondary hot (switched leg- call for heat from thermostat) goes to terminal TH-W and NOT to terminal 24V in most cases, if there is not automatic vent damper.