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Old mueller furnace co gas era boiler

 Can anybody tell me what I’ve got? it works I don’t think it works right aquastat set to 200 can’t get out no more than 120° out of it pressure good gauge and top of boiler works. I just cleaned out the burner cleaned out the inside I need to flush it I don’t know where to start. Can find very little information on something this old online. Thermostat on the wall calls for heat upstairs and the burner kicks on and the circulator pump. I wired  the circulator pump to run constant today just to see if I had any change.  Any insight anybody has point me in the right direction would be great. Thank you


  • Jlscott18
    Jlscott18 Member Posts: 4
    Some pics didn’t upload the first post
  • mattmia2
    mattmia2 Member Posts: 8,437
    What is it connected to? It may be underfiring or it may be connected to a system with a lot of mass to heat. Either way you need to find a pro that understands older boilers to make sure it is burning properly and test the safeties.
  • Jlscott18
    Jlscott18 Member Posts: 4
    Old cast iron radiators. All the safety features seem to work. I’m curious why the burner and pump basically run all day long in the winter. It shuts off when temperatures is Met upstairs. But shouldn’t it fire to heat the water and the pump run when heat is called for?
  • bburd
    bburd Member Posts: 684
    Sounds like you have a "cold start" boiler. Many of the old gravity conversion jobs were wired that way. You save fuel by not keeping the boiler hot all the time. With a high mass system like that there is a risk of flue gas condensation, but those old cast-iron boilers were so heavily built that it may not matter. I had one firing oil and it was 50 years old when I sold the house.

  • Steamhead
    Steamhead Member Posts: 16,279
    @Jlscott18 , where are you located? We might know someone who can help.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • Jlscott18
    Jlscott18 Member Posts: 4
    Iowa. I flushed the system refilled it the pressure valves worked bled all the rads drained the expansion tank and charged it with air cleaned the burners checked my fuel pressure. The thing always works out just runs non stop. All my temps are really close at the boiler return and out and at the radiators. Of course it is still 75 degrees outside but it gets up to whatever I set the aquastat to and kicks the burner off. But I am pretty sure if I demand heat at the thermostat the burner is going to fire. Shouldn’t just the circulating pump run if the boiler is at the set aquastat temp?