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aquastat low setting during summer months for oil boiler

moey Member Posts: 40
I have a Burnham V-14A (oil) with a indirect hot water setup. What are the

optimal settings in the summer months on the aquastat to not have the

boiler cycle as much maintaining temperature. I currently have the low

set to 140 with a diff of 15 and it cycles every 2-3 hours if there is

no call for heat. The aquastat is a 8184H with high/low/diff settings.

Is it ok to turn the low settings on the aquastat down further in the

summer? My thinking is that the coldest water coming in would then be

from the indirect and it would be around 110 and the boiler would fire

off at that point getting above the condensation point quickly.

I understand in the winter the low settings would have to be turned back

up again as the water coming back would be colder.


  • STEVEusaPA
    STEVEusaPA Member Posts: 5,882
    few quick questions....

    You say you have an indirect hot water heater.  How is that controlled? Is there an aquastat on the indirect?  If so,  do you also have a mixing (anti-scald) valve piped in between the cold water coming into the indirect and the hot water coming out? If so, here's my recommendations:

    1.. Keep the indirect tank temp above 140 degrees (with the indirect aquastat), and mix down to a lower temperature to prevent scalding.

    2.  Turn the low limit on the boiler aquastat all the way down.  If you domestic hot water keeps up with demand, leave it like that for the summer.  If it doesnt keep up, turn it up 10 degrees, try again for a day or 2.

    If you do not have a separate aquastat controlling the indirect, you could install one with a different control strategy.

    If you boiler aquastat controls the domestic hot water demand, you could lower it 10 degrees, try it for a couple of days, or raise the diff all the way up.

    Either way, it helps if all the pipes are insulated.  In my case, with an aquastat on the indirect, in the summer, my boiler only runs 2 or 3 times a day with regular use.  Yours is running every few hours because the aquastat control is trying to maintain that temperature, and your boiler is losing probably around 10-15 degrees per hour.  The indirect temperature is held much better, the reason why you should try to control your hot water demand off of the indirect temperature.
  • moey
    moey Member Posts: 40
    edited February 2012

    The indirect is controlled through the honeywell 8182H controller on the boiler, when there is a call for hot water (if the tank drops far enough below the 120 degree setting) the circulator on the indirect comes on and the boiler starts.

    I do not have a anti scald valve. Id like to turn it up to 140 (indirect temperature) but we have small children so I dont think that would be wise.

    I have some confusion I think.  Does it matter what my low limit is set to on the boiler aquastat in terms of making hot water? It seems like the indirect kicks on the boiler and runs it up to the high limit so the low limit does not matter in this case or for that matter the boiler temp does not matter. The indirect runs it up to the high limit. 

    The low limit only matters in terms of condensation I was under the impression.

    Please correct things I have said that may be inaccurate in my assumptions.
  • STEVEusaPA
    STEVEusaPA Member Posts: 5,882
    just to clarify....

    your aquastat........r8182, or 8184?  you said 8184 or first post and 8182 on second.  I think you mean 8182.  Anyway, are you sure you see no wires coming out of the indirect hot water heater? low voltage wires? Seems odd, but not unlikely that the indirect is run off the boiler temperature and not the indirect tank temp.  When you say "if the tank drops far enough below the 120 degree setting) the circulator on the indirect comes on and the boiler starts". in order for the boiler to know the tank is below 120", it has to have an aquastat measuring the temp.

    And to further clarify, when you say indirect, we're talking about a separate tank from the boiler, looks like a hot water heater, and not a coil, in the boiler for making domestic hot water?

    Pics would always help.

    But to answer one of your questions, when there is a domestic hot water call, the burner comes on, 10 degrees below your lo limit setting, and runs shuts off at your low limit plus your differential.  In your case from 130 to 155.  It shouldnt run it up to your high limit. Your hi limit should be set to 190.  If it does, that tells me your boiler cant get the btus over to the indirect fast enough (circ bad, piping wrong).
  • moey
    moey Member Posts: 40
    edited February 2012
    controller is R8182H

    sorry got confused a bit. Attached a picture. Yes there are wires coming from the indirect to the boiler.

    My main question is whether it is detrimental to the boiler to turn the boiler low setting down to 120 during the summer on the aquastat, or whether there will be condensation issues.

    I figured if I experienced a shortage of hot water or long cycles trying to make hot water that would answer that question on its own.
  • STEVEusaPA
    STEVEusaPA Member Posts: 5,882
    ahhhhhh...now were getting somewhere....

    It appears your boiler, for domestic hot water is controlled by your indirect.  Yes you can turn your low limit all the way down.  When the temperature drops in the indirect, the aquastat in the indirect, will call the boiler to fire.  Of course if I'm wrong (hard to tell from the pics) you will have no hot water, and will have to turn your low limit back up.

    I don't think you'll have a condensation problem.  Your boiler is going to fire at least 3 times a day, and after a DHW call, the boiler is going to be up to a  temperature of about 170/180 degrees.  Youll problem see the temp drop no lower then about 100-110 degrees.  And when the boiler fires, you'll be above condensing temps rather quickly.

    Of course, nothing beats what actually happens as your true measuremnt.  Take a look inside the flue pipe, note what or what not is in there.  When you get your annual tune-up/inspection this fall, tell the tech what you did and ask him if sees any difference, good or bad, or any problems.  This would tell you if your system is going to been fine adjusting it as you wanted.

    Just another thing, it is recommended to get the temp up in the indirect above 140 degrees to discourage the growth of legionella.  I strongly recommend you have a mixing valve installed, set your indirect aquastat higher, and mix down to a safer temperature.
  • moey
    moey Member Posts: 40

    Thank you very much for your insightful help. Its a new house (to us) so Im still trying to figure it out. I had a cleaning done about 6 months ago and they walked me thru the system and explained it to me, but you can only absorb so much and it was late fall so I didnt think to ask questions about aquastat settings. 
  • billtwocase
    billtwocase Member Posts: 2,385
    As Steve said

    You have an 8182H control, Smart control that is evidently tied into Z-R to run it up to high limit. I would turn the low limit as low as it will go. It will still maintain about 110, and set the high limit at 180. These controls are always off a good 10-20 degrees due to the length of the capillary tube supply line. I there an old abandoned coil where the control sensor goes? If not, you could cold start this using that same control.
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