Aquastat settings

Discussion in 'Boiler Forum' started by tedlaw, Dec 24, 2013.

  1. tedlaw

    tedlaw New Member

    Dec 24, 2013
    Fernie, BC
    I have a series 2 B, Burnham Boiler. My water pressure gauge shows 15 psa. My water temp. will not go above
    140F. The dial on the Honeywell aquastat attached to the boiler is at 230 @ the 12 oclock indicator.
    Should I move that higher to attain an uper limit of 175 or so?
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    The boiler may only go higher if there is a call for heat...the thermostat may not be asking for heat, or the controller is not recognizing it. 230-degrees is likely way too high - to operate there, the system pressure would likely need to be higher to be on the safe side...if there were ever a leak, 230-degree water flashing to steam will ruin your day if you're still around and alive to see it.
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  4. Soapm

    Soapm Member

    Dec 18, 2013
    Aurora, CO
    Not to thread jack but I'm curious, what makes their boiler stay below 140 unless there is demand? That seems like a smart, energy saving idea. Is it possible to make our boiler do this?

    We have a natural gas Hydrotherm R250C with a Honeywell L8148E controller.
  5. DonL

    DonL Jack of all trades Master of one

    Mar 30, 2011
    Rocket Scientist
    Houston, TX

    I am no pro on the subject.

    I do know that it is not good too go tweaking on the controller, unless you have the proper instruments and know how.

    Once you jack around with the control, It can be hard getting it back to factory recommended settings.

    Have Fun.
  6. Tom Sawyer

    Tom Sawyer In the Trades

    Nov 29, 2010
    The L8148 is a single high limit aquastat that shuts the boiler off at a set high temperature, usually 180 to 200 degrees. It has a built in 15 degree differential so the burner will come back on on a 15 degree drop. There are no other adjustments to that control. It also serves as the burner and circulator start relay. The L8124 has both a high limit and a low limit. The low keeps the boiler at a set temperature if you have a domestic hot water coil in the boiler. It has an adjustable differential also that should be set at 10 degrees normally. Normally an L8124 would be set at 160 for the low and 180 for the high.

    Sometimes older boilers, especially cast iron ones, need to maintain temperature or they leak between the sections at the push nipples. However, if that is the case, the boiler should be replaced as soon as possible because keeping a boiler hot 365 days a year is a huge waste of money.
  7. Dana

    Dana In the trades

    Jan 14, 2009
    IIRC Burnham 2s have two aquastats, one of which is the operational control, the other is a safety high-limit. The operational control on that boiler only kicks in when there is a call for heat, and the boiler temp will drop well below the low the low-limit temp. Tweaking the safety high-limit aquastat won't affect the temp, the other will. IIRC they are both located inside the slip-on panel at the front of the boiler, and if you are tweaking an external aquastat it may be an installer-applied control providing another function.

    Have you consulted the manual for your exact model & series? (Burnham 2s have been around forever, with multiple variations on the theme.)
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