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Two stage thermostat

It is oil. I'm still interested in the procedure.
Ill check out the oil sites


  • Rick Rodriguez_2
    Rick Rodriguez_2 Member Posts: 23
    Two stage thermostat

    Hi Carol:

    I moved into a house a hot water boiler that is over sized. To keep it from hitting limit or minamize the time it turns off full of hot water I'm considering a two stage thermostat or an out door reset. What are the pros and cons of these controls and what is the increase of efficency I can expect.
  • carol_3
    carol_3 Member Posts: 397

    To use a 2-stage stat you need a boiler designed with hi-fire and low-fire. I bet you don't have that, so a 2-stage stat would do anything for you. Outdoor reset is designed to give you lower temp water as it gets warmer outside so that might work. The high limit is a separate controller from your operating thermostat/aquastat. The water temp controller should be set enough degrees below the high limit that you don't reach high limit unless somethings really wrong. I'd try reducing the water temp first with the controller you have, outdoor reset second. I haven't a clue about efficiency of either.
  • Empire_2
    Empire_2 Member Posts: 2,343

    I guess my question would be, Why do you think the boiler is oversized for the house? As far as boilers reaching it's temp of 180* that's what they are supposed to do unless instructed otherwise by the addition of controls. 2 stg stat has no bearing on this situation because we don't know what you have to begin with. More info would be great if you can provide it...
    Mike T......
  • Rick Rodriguez_2
    Rick Rodriguez_2 Member Posts: 23

    By doing a heat loss calculation
  • Rick Rodriguez_2
    Rick Rodriguez_2 Member Posts: 23

    I have used a two stage themostat on a hydronic sysem that did not have a dual firing rate. First stage would wired to operate the circulator 2nd stage would pull in the burner. This set up obvously saves energy. I would like to be able to determine the payback peroid. Have any ideas where to find this information.
  • Empire_2
    Empire_2 Member Posts: 2,343

    I was just checking as to why... OK... I am not sure where to get the info on the exact savings (vs) how you are setting the system up. Why not just use an outdoor reset control to modulat temp instead on cycling a pump off of the 1st stage and actually cycle the boiler off the 2nd stage. To me this is inefficient. If you only drop 1 or 2 degres, why cycle the pump without temp control? the pump can be circulating a wide range of water temps that may or may not satisfy the stat. electric is being wasted. You are counting on the temp in the room to drop about 3* and then fire the boiler thus relying on residual heat to hopefully be enough to serve the space after the 2nd stage kicks out.. I dont see it.
  • Rick, is this a gas or oil boiler?

    If it is gas what is the make? Some boilers can be retrofitted to a two stage gas valve. It involves doing a combustion turn down test to determine if the boiler will fire properly with a low fire input. If you contact me I have a written procedure for doing this on certain boiler systems.

    I would also suggest doing a combustion analysis on the system to get it firing at its maximum efficiency.

    If it is oil I would yield to someone with more knowledge than I have on oil. You might if it is oil contact WWW.oiltechtalk.com or www.firedragonent.com
  • Wayco Wayne_2
    Wayco Wayne_2 Member Posts: 2,476
    I've used

    a 2 stage like you said, with the first stage running the circulator and the 2nd stage running the burner. I used it to keep copper fin basebaord from getting too cold. I dont know if it would help with a boiler that's too big. If yu have the room you could install a buffer tank. WW

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