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National US gas boiler questions??? boiler no. 4-22a

swkargo Member Posts: 4
Old gas boiler. Unit starts when heat is needed. Room heats up and is satisfied. water flow and gas shut off. Boiler temperature only gets to 120/130 degrees. aqua stat set at 160 degrees. Is this normal? Any help would be nice..


  • Tim McElwain
    Tim McElwain Member Posts: 4,593
    What is the number and make of the aquastat

    control on the boiler? A picture would help!

    No the boiler water temperature for heating should be higher than that something may be set wrong or some restriction to flow.
  • Mike Kusiak_2
    Mike Kusiak_2 Member Posts: 604
    High mass system?

    Does this system have large cast iron radiators and a high water content? A converted gravity system? If so, your water temperatures may be normal in fairly mild weather. With a high mass system, it takes a long time for all that iron and water to heat up, so the room thermostat may be satisfied long before the aquastat high limit is reached. In colder weather, the water temperatures will rise higher and then may then reach the aquastat setting. This type of operation was fairly typical for hot water systems built before the 1960's and is well described in the Bell and Gossett handbooks of the time. It actually behaves as sort of a "natural" outdoor reset, modulating water temperature as a function of outdoor weather conditions.

    Baseboard fin-tube systems act entirely differently. They are low mass, so the water temperature rises quickly and the high limit is reached on almost every call for heat before the thermostat is satisfied.
  • swkargo
    swkargo Member Posts: 4
    edited November 2011

    Pictures of controls
  • swkargo
    swkargo Member Posts: 4

    I do have the old cast iron. I just thought that the boiler should be hotter. When it is satisfy and shuts off the temp will go back to ambient temp. In the house as in this photo.
  • Mike Kusiak_2
    Mike Kusiak_2 Member Posts: 604
    Cold start system

    You have what is known as a cold start system. On a call for heat from the thermostat, both the circulator pump and burner turn on. The boiler temperature rises from ambient room temperature until the thermometer is satisfied. In spring and fall weather the boiler may only rise to 120 to 130F as radiators at that temperature can supply all the heat necessary to meet the building heat loss. As the outdoor temperature decreases in winter, the boiler needs to run longer to supply enough heat to maintain indoor temperature and the boiler water temperature will rise higher toward the aquastat limit setting.

    I believe that as the weather gets colder, you will notice the boiler will reach higher and higher temperatures, and on a very cold day you will reach the aquastat setting where the burner will shut down while the circulator continues to run until the romm thermostat is satisfied.
  • lchmb
    lchmb Member Posts: 2,997
    it could

    just be the guage isnt accurate....
  • swkargo
    swkargo Member Posts: 4
    cold start

    Thanks for the information. Any way to up grade this older boiler less than replacing it. Also does anyone have the program for doing a house energy assessment. Measuring window doors etc. Thanks to.all who help me..
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