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Tips and Tools to tweak and optimize a system and Outdoor Reset Curve

I am a homeowner, don't hold that against me though, and wanted to share some tips on tweaking and optimizing a system and Outdoor Reset Curve. At the beginning of the heating season, I got a new Mod-con system installed and now every radiator in my house has a direct run from manifolds with flow setters. I now have control over my system unlike before.

I am using 2 things to help me tweak and optimize the system, that I thought people might want to know about.

1st, thermometers. I went on ebay and picked up 1/10 of a degree digital probe thermometers for about $1.25 a piece shipped. I got 4, 1 of the 4 is half a degree low but the price is great. I use these to balance each part of each zone. This has really helped me get the zone internally balanced. Below is the link

Next I put hour meters on each zone. On ebay again, I found hour meters that will work on 24VAC under $9 each shipped.
Each of my 3 zones now has an hour meter on it so I am recording the time that each zone is calling. After 2 weeks of observation, my 3 zones are calling 60%, 37% and 35% of the time. Based on this I plan to add radiation to the zone that is calling 60% of the time so I can get all zones to call about the same amount of time. Also I can see that based on this and the outside temp that I can turn down the supply water temp. Can I get the supply temp low enough to get the zones to call 80% or more of the time? Maybe, I guess I will see what I can do.

Hope this is useful for others,

John R.



  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,630
    This is good data you are collecting. You will be on your way to near constant circulation. Great job!

    By adding radiation to get all 3 zones close in operating time, and by then modulating temp to get those run times up you will be getting close to every btu available out of the fuel.

    Hats off to you, money saved is money earned!
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!
  • johntrhodes81
    johntrhodes81 Member Posts: 35
    Over the summer I almost doubled the radiation in the 60% zone to get it closer to the 35% zone, which is also on the 1st floor. I also fully insulated the basement walls. Which I didn't account for adding radiation. The zone that called the least was the upstairs at 30%.

    Now after the adding the radiation and insulating the basement, the first floor zones are getting closer to calling for heat about the same amount but now the upstairs which used to call for heat the least is now calling for heat about 3.5 times more than the 1st floor.

    I guess what I am saying is insulating an insulated basement with r20 of spray foam can make a huge difference.

  • Paul48
    Paul48 Member Posts: 4,469
    Any room in the attic for more insulation?
  • Harvey Ramer
    Harvey Ramer Member Posts: 2,239
    Keep in mind that if you get all zones to run 80% to 90% of the time, you may find the system unable to do the job on a windy day. Unless your house is super tight with controlled air exchange.
  • johntrhodes81
    johntrhodes81 Member Posts: 35
    Funny you should ask about the attic. It is only partial fiberglass insulated 2x6 raftered Cape Cod. I am about to reno the whole 2nd floor and super insulate it.

    Good point on wind.