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How to determine set back recovery time

I manage 5500 square foot building that is only used once or twice a week. Last year, we heated to 68* every day and set back to 60* at night and used 5500 gallons of oil.

This year, I want to try keeping the temp at 50* and only turn it up for the day or two a week when the building will be used. I realize that the recovery time could be lengthy and the comfort level will not be the same as otherwise, but economic times are different now. The big question is how long it will take to warm the building.

If I measure the time required to raise the temperature for a specific delta of temperature, I am guessing that I can calculate the recovery time required for any temperature. Yes, I know that wind and sunshine will affect the results.

For instance, if the temp is 30* and I start the boiler and it takes five hours to raise the temp from 50* to 68*, then is there a formula that I can use to calculate the same for 20*, 10*, etc. And then the question of at what outdoor temp will recovery not be practical or possible.

Anyone care to share your ideas? This is not your typical home set-back.



  • steveex
    steveex Member Posts: 95

    Mr. steve check out tekmars 512 stat, it has an adjustment for that purpose.
  • jp_2
    jp_2 Member Posts: 1,935
    paper, pencil

    watch and a thermometer!

    all the tools you need to figure out heating times.
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,576
    only once or twice a week

    if you know when the building will be used, would a visionpro stat with intelligent recovery work?
    i believe it can "learn" the time it will take to raise the temp.
    also is the system in good shape? i see you are a "frequent flyer" on this website, so i am sure you know as well as i that a "deferred maintainance" system could be more unpredictable than one in the pink of health [setback-wise]!--nbc
  • Steve Garson_6
    Steve Garson_6 Member Posts: 35

    The system is in relatively good health. It's well cared for but oversized.
  • Jay_14
    Jay_14 Member Posts: 39
    tekmar tN4

    tekmar's tN4 product line is specifically designed for large setback applications and takes out all the guess work. The thermostats have two features required if you want to do large temperature setback:

    1) Optimum Start - basically the thermostat learns the heat up rate of the room.

    2) Indoor feedback - the thermostat works together with the boiler reset control to change the boiler target. If the room is very cold from a deep setback, then the boiler target is ramped up so that the room is warm at the correct time.

    If you simply install a thermostat that has Optimum Start or equivalent, there is still no guarantee the room will be at your desired temperature at the desired time.

    If interested, see www.tekmarcontrols.com for more information.

    Jay Vath

    tekmar Control Systems
  • Steve Garson_6
    Steve Garson_6 Member Posts: 35


    Can you elaborate? I went to the web site and it sounds like the TN4 is a whole line of products. Would we need just the 542 and the 070 outdoor sensor? Or do we even need the outdoor sensor?

    Our application is simple: steam boiler, one zone, heating a ballroom. Our programming schedule may change, i.e. in use Thursday one week and not be used the following week. We have an office manager who controls the T-stat. She has an electric baseboard in her office:)

    We're in Boston.

  • steveex
    steveex Member Posts: 95

    Read about the tekmar 512, very simple
  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928


    Nearly every modern electronic setback thermostat uses some form of "smart" recovery. While it will take a number of heating/setback cycles to learn, eventually it will turn on the heat at the proper time to get the space heated by the time you set.

    Do though be aware that at the end of recovery, about the only thing that will be up to temp is the air itself. Walls, furnishings, etc. will likely be much cooler and you can easily set up very uncomfortable conditions for a large crowd. (This is especially true for a poorly insulated masonry structure.) To keep occupant complaints to a minimum, you'll likely have to experiement a bit to determine how long before you expect a crowd to set the recovery time to end and allow the air and structure to achieve a better balance.
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