All of the line voltage controls are essentially switches. Power runs through the service switches and then though the low water cutoff, the high limit aquastat and the low limit aquastat and finally, down to the oil burner primary control. A leg of the high voltage also feeds the SR relay panel as well as the low limit side of the aquastat. All of your low voltage thermostats get wired to the TT terminals on the SR relay. All of the circulators get wired to the circulator terminals on the SR relay ( right below the TT terminals to keep wiring straight ) The TT terminals on the SR relay get wired to TT on the oil burner primary control. You can find all of the diagrams here.