Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.
If our community has helped you, please consider making a contribution to support this website. Thanks!

Oil boiler high/low temp

Options
jmoser201
jmoser201 Member Posts: 4
edited December 2021 in Oil Heating
Recently moved into a home that has an oil boiler which provides hot water for baseboard heating and an indirect hot water tank. I just had a plumber/hvac guy out to replace the expansion tank and he noticed the Honeywell high/low setting which is currently set at 180/160 with a diff of 10. He said the low was set too high and put it at 120. I researched and that seems way too low for an oil boiler, but I’m not an expert. Does anyone know what the best settings would be for my system? It’s a peerless boiler from 1989

Comments

  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
    edited December 2021
    The first thing to determine is if the knobs are measuring the boiler temperature accuratly.
    Do you have a tankless coil (coil inside boiler to make domestic hot water) or an actual indirect storage tank?
    You must have a mixing valve to temper the water reaching the fixtures, in either scenario.

    If you have an indirect, I would change the aquastat to something like a Hydrostat 3250 plus. Make it cold start, low limit off, and utilize circulator hold off, as well as the other features.

    If you have a tankless coil, the temperature of the incoming cold water directly affects the domestic hot water output. Right now 120/160 might be fine, but when your incoming cold water gets down into the high 30's/low 40's, you won't get the hot water you need for showers.
    If it is a tankless coil, you need to realize you are making domestic hot water in the least efficient, least consistently comfortable manner, with ancient technology.

    There was an error rendering this rich post.

    MikeAmann
  • jmoser201
    jmoser201 Member Posts: 4
    STEVEusaPA said:
    The first thing to determine is if the knobs are measuring the boiler temperature accuratly. Do you have a tankless coil (coil inside boiler to make domestic hot water) or an actual indirect storage tank? You must have a mixing valve to temper the water reaching the fixtures, in either scenario. If you have an indirect, I would change the aquastat to something like a Hydrostat 3250 plus. Make it cold start, low limit off, and utilize circulator hold off, as well as the other features. If you have a tankless coil, the temperature of the incoming cold water directly affects the domestic hot water output. Right now 120/160 might be fine, but when your incoming cold water gets down into the high 30's/low 40's, you won't get the hot water you need for showers. If it is a tankless coil, you need to realize you are making domestic hot water in the least efficient, least consistently comfortable manner, with ancient technology.
    We do have a 35 gallon storage tank, so the boiler is creating the hot water and storing it in the tank. I’m assuming we have a mixing valve, because the water comes out of the faucets at a normal temp of 120 or below
  • jmoser201
    jmoser201 Member Posts: 4


    Here are pictures of the full setup 
  • HVACNUT
    HVACNUT Member Posts: 7,191
    As long as the valve feeding the tankless coil is off, do as @STEVEusaPA mentioned and look into the Hydrostat 3250 Plus. 
     
    A safer primary control couldn't hurt either. 

    Also the 3 section JOT was always a tight boiler and the evidence is on the jacket around the front plate. A thorough cleaning and replacing the kaowool rope gasket around the front plate would be good.
    MikeAmann
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
    I'm having a little difficulty understanding your picture, maybe move to the right a little. It doesn't appear to be piped correctly. Looks to me the water can flow thru the coil and completely bypass the tank.
    Usually with your arrangement, cold water flows thru the coil, and the outlet of the coil goes to the inlet of the tank, and the outlet of the tank goes to the fixtures.
    Also I don't see a mixing valve.

    There was an error rendering this rich post.

    Robert O'BrienMikeAmann
  • Robert O'Brien
    Robert O'Brien Member Posts: 3,584
    STEVEusaPA said:

    I'm having a little difficulty understanding your picture, maybe move to the right a little. It doesn't appear to be piped correctly. Looks to me the water can flow thru the coil and completely bypass the tank.
    Usually with your arrangement, cold water flows thru the coil, and the outlet of the coil goes to the inlet of the tank, and the outlet of the tank goes to the fixtures.
    Also I don't see a mixing valve.

    Agreed, it looks teed in, although the path of least resistance is through the tank, eliminate the coil completely. Cold start the boiler, the indirect will call often enough to prevent condensation.
    STEVEusaPA
  • jmoser201
    jmoser201 Member Posts: 4
    Robert O'Brien said:
    I'm having a little difficulty understanding your picture, maybe move to the right a little. It doesn't appear to be piped correctly. Looks to me the water can flow thru the coil and completely bypass the tank. Usually with your arrangement, cold water flows thru the coil, and the outlet of the coil goes to the inlet of the tank, and the outlet of the tank goes to the fixtures. Also I don't see a mixing valve.
    Agreed, it looks teed in, although the path of least resistance is through the tank, eliminate the coil completely. Cold start the boiler, the indirect will call often enough to prevent condensation.
    Ok, so you’re saying I should be fine to leave the low set to 120?
  • HVACNUT
    HVACNUT Member Posts: 7,191
    With the valve off on the cold at the tankless, only the indirect will see the draw.
    I guess if the indirect fails (relay or circulator), the hot and cold can be closed at the indirect, open the cold at the tankless and use it temporarily. 
    It can't be wired cold start though in that case.

Categories