Gas and Oil Home Heating Furnaces - hydronic circulator won't stop

My hydronic system is acting up! The cirulator will not stop. I bleed the system both at the h2o drain valves and air bleeders. The pressure got up as high as 20 lbs and is now falling. Now the burner cut off (when it matched thermostat)return h20 is warm and h2o leaving the burner is only high warm.Pressure is about 16, I thought it usaully stayed about 10-12? Have I let too much fresh water in? I'm unsure about proper adjustment of h2o water reducer. It seemed like the pressure was rising as I allowed more in, so I closed it back to where I thought it was when I started.

If you only have one circulator,set tstat to 50.If circ. still runs the relay has gone south and contacts all stuck.PDF

PDF- Thanks. That sounds like a solid diagnosis. Yes it does stay on even when t-stat is all the way down. Is the relay in the gray control box? I hope/ assume it can be purchesed separatly? I shut the whole system down last night to prevent burning up the pump,(it was getting hot) since I can't get parts until Monday do you think I should periodically shut it down until then? Thanks again- This is one of the most valuable sites I've ever found on any subject.

PDF- I located the relay and gave it a light tap and that released it. It is part of an old 1964? Honeywell control box, does not look like it replaces separatly. The pressure is about 12-14 lbs, is that about right? It's three small stories, 3 zones. I think it was set around 10-12 before. Am I correct that the only way to adjust this is to adjust the inlet h2o and then bleed off at the pressure relief valve if too high? I've always longed for a source for info on subjects my father is unsure of. I'll never be able to thank him enough for never drawing a line between mens work and womens work and given me the strength to tackle (or attempt to) whatever comes my way. I hope all your readers give your daughters the same strength and courage!