OPD....Overfill Protection Device
OVERFILL.....NOTHING to do with 'Vapor' coming out just a float that shuts off 'Liquid' going in when refilling
Opening the OPD/Service Valve too quickly can trip the 'Excess Flow Device' which is in the Pigtail ACME Nut (or fitting on MHs). Nothing to do with the OPD/Service valve
Propane Changeover/Regulator
Lever points to Cylinder IN service. Then when that cylinder drops to >10# the changeover swaps to other cylinder. RED flag on indicator/move lever to point to other cylinder/GREEN flag on indicator
ACME Nut has 'stub' that pushes open the Spring Loaded Shutoff Valve (internal part of OPD/Service Valve). IF ACME Nut not tightened the shutoff valve will not open so no vapor can flow (If you open OPD/Service Valve w/o ACME Nut/Pigtail Hose installed NO propane will flow out)
