hal,as far as i know the boiler starts on outside air temp and return water temp.not all valves have spring return, some have 24v at the valve all the time and use a signal provided through a electronic controller or t-stat to tell the valve which way to go.
r is one side of 24v w is for heating and i have never heard of t&t. i think you may be the one with bad info. i highly doubt that a end switch on a valve is going to start the boiler, unless maybe the boiler is in florida where they dont need heat.
