Thanks for all your help. I had posted a problem with a Vallilant boiler that had an intermitent problem with the burner kicking off and not igniting again until the thermostat was reset. I did call and expert, and he found the problem in five minutes. It was the Aquastat. Since its replacement, the boiler is like new again - burner burns to 180 and kicks off, water temp drops to 160 burner kicks back on until it reaches its setpoint. Radiant heat is the best!
Thanks for help! Great site!