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Thread: Honeywell Aquastat Settings

  1. #1


    Thanks for Your Help HOW DO I DELETE THIS??????????
    Last edited by JoeD; 12-21-2005 at 07:23 PM.

  2. #2


    Ours is GV-5, the same manufacturer like yours. I keep the settings to 155F -180F since the installation for about 15 years. I think the low is predetermined automatically. These settings are easier on the system and you will save some money, maintain higher temperature is more expensive. However, if you desire quicker rooms warm up is OK to set the limit higher. In same cases when the heat loss is too extensive you may have no choice, just keep on higher limit.

    I need to know if your boiler has a sealed combustion before I will try to answer the second issue.
    I hope this will help.


    Last edited by pkrsiak; 12-14-2005 at 04:17 PM.

  3. #3
    Plumber/Gasfitter dubldare's Avatar
    Join Date
    Sep 2005



    High Limit Controller
    The high limit opens and turns off the burner when the
    water temperature reaches the set point. The high limit
    automatically resets after the water temperature drops
    past the set point and through the 10F (6C) differential.
    Low Limit and Circulator Controllers
    On a temperature rise, with the adjustable differential at the
    minimum setting of 10F (C), the burner circuit (R-B) breaks
    and the circulator circuit (R-W) makes at the control set point.
    On a temperature drop of 10 F (6C) below the set point, the
    R-B circuit makes and the R-W circuit breaks. See Fig. 22.
    At any differential setting greater than 10F (6C), the R-B
    make temperature and R-W break temperature will remain the
    same (control setting minus 10F (6C). The R-B break and
    R-W make temperature will be the set point temperature plus
    the difference between the differential setting and 10F (6C).
    EXAMPLE:Set point of 140F (60C) differential set at 25F
    (14C). On a temperature rise, R-B will break and R-W will
    make at 155F (68C). On a temperature fall, R-B will make
    and R-W will break at 130F (54C).

    I'd keep your high limit setting around 200-210.

    As far as operating temp, with baseboard heat, I'd top out at 190 max, radiators 160. This will vary depending on your differential setting.

    One can have alot of trouble with running a boiler to cool. Not only for condensation purposes, but also for adequate combustion of the fuel. Generally speaking, a 'hotter' boiler will burn much cleaner (emissions wise) than a cooler one. Such settings can really only be known by evaluating your houses heat load, size of radiation and location, boiler size, combustion efficiency and circulator size/flow rate.

  4. #4
    Plumber/Gasfitter dubldare's Avatar
    Join Date
    Sep 2005


    I replaced the Relay because my burner clicks on Ignites for 30-90Sec and then pops off. I STILL have this problem (ie Burner Turns Off after short run time) HELP!!!

    Without knowing a lot of info on your set-up, I'll throw out a laundry list of potential issues.

    Thermostat heat anticipator, faulty circulation pump (more common than one might think), low water pressure (leading to inadequate circulation), faulty high limit control (if another exists besides the aquastat), loss of flame sense/poor pilot flame (particularly White-Rogers mercury systems), flame roll-out switch (dirty boiler/ if equipped), weak 24v transformer/low voltage wiring, weak coil in gas valve, poor gas pressure, partially plugged flue (induced draft systems). That all I can guess off the top of my head.

  5. #5
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    Cave Creek, Arizona

    Default relay

    That is probably a combination aquastat/high limit control. The high is where the safety would kick in to turn the burner off. The low is the normal operating temperature and the diff is the amount that the temperature will change, usually downward, before the burner starts again. Before changing the relay you should have checked it and everything else to find out the real problem. You still have to do that, but there are many possibilities, low circulation being one of the most likely, although your on/off cycles seem to be to short for that.

  6. #6

    Default pkrsiak Sealed or UNsealed Combustion ???????

    Not Sure!
    I can open up a hole on the front of the boiler to see flame is that
    sealed or unsealed combustion.


    Last edited by JoeD; 12-15-2005 at 08:20 PM.

  7. #7


    Is your boiler direct vent? If is then you most likely have a sealed combustion. There are sensors controlling for a proper air-gas ratio. If one of them is insufficient or the exhaust is blocked the system will shut down, or the sensors could be faulty

  8. #8
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    New England


    Normally, a sealed system is just that, you can't see the burner in operation.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014


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