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Tired of tstat turning off heat

ceikey Member Posts: 60
I know its not deep heating season yet, but I'm tired of watching my boiler make steam, heat up all the pipes only to be kicked off by the tstat when the rads are barely half full. Wouldn't it be better if the rads got completely hot then the tstat kicks it off and I get the full "coast down" of the rads providing heat with the boiler off? Is there a way to control the cycle better to make this happen? Is there a tstat with a bigger swing than +/-2 deg from set point which would allow for a longer heating cycle? I appreciate your thoughts.



  • rads only part way full

    as a test , you can put a temporary jumper on the thermostat wires and let the boiler run until all radiators are completely hot. after that, take the room temperature.  i think you will find that the inside temperature is too high for comfort or economy.

    this is like the operation of a car. you don't accelerate to maximum speed, and then coast as far as you can.

    if the outside temperature were at your design temperature [lowest temperature regularly seen], then you might see all sections of your radiators fully hot, but not at milder winter temps.

    this is not to say that your thermostat is controlling the system perfectly. you may have maladjustment there. if it will maintain the temperature constantly at the set-point, then it is probably ok.--nbc
  • crash2009
    crash2009 Member Posts: 1,484

    1-I had a similar problem recently.  In my case the thermostat was shutting down the boiler before the steam had travelled to the farthest radiators.  I was advised to solve the problem with venting, not by moving the thermostat.  I went after the venting on the radiator closest to the thermostat.  As it turned out there was a Ventrite adjustable 1-8 on that rad.  It was set to 8, I changed it to 2.  Now the boiler runs longer because it takes more time to heat the room with the thermostat.  The room with the thermostat still gets up to temp, and the farthest rads have more time to fill.

    2-New boiler, New thermostat:

    Did you put in a new thermostat when you did all that work last month?  If so, did you adjust the cycles to work with steam?  Most new thermostats, out of the box are set for forced air (6) not steam (1)

    3-New boiler-old thermostat:

    Sometimes the voltages are incompatible   
  • David Nadle
    David Nadle Member Posts: 624
    Large swings are uncomfortable

    A wide swing will likely lead someone in your household to feel cold and turn the thermostat up just as it's about to come on anyway. Later they'll feel too hot and turn it back down plus open some windows. Rinse and repeat. Crash's questions are essential: make sure your thermostat is set to one cycle per hour. The best thing you can do to reduce the number of cycles is tighten the house envelope.
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    Sometimes the voltages are incompatible

    Did I ever find that out. Someone gave me a digital programmable thermostat, so I replaced an old GE thermostat that used a permanent magnet instead of an anticipator in it. I had wide swing because the heat went into a slab, and the boiler water was too hot and the boiler was oversized (I did not know that). I tried diddling the anticipation, but no relief.

    I thought the digital would have a smaller dead zone and help. So I put the digital one in and it fried immediately. The old thermostat controlled the big circulator that ran at 120Volts, and the digital one expected 24 volts. I am glad I did not have to pay for that thermostat. They still make thermostats a little like that for resistance electrical heating systems, I understand. Saves them the price of a power relay.
  • ceikey
    ceikey Member Posts: 60
    fill the rads faster???

    Thanks for all the comments.

    Crash, I put all new hoffman 1a's on when the boiler went in. I have the rad nearest the tstat at #1 setting. The rest of the rads are adjusted accordingly to the location and riser/runout length. I admit they aren't perfect yet because I still have to insulate the mains. (Going to the insulation shop you referred me too today after work). I figure things will change a bit once I insulate.  But they are all getting heat approximately the same time.

    I did put a new tstat in and it is set to steam, but not sure if that means it will cycle one time per hour.....is that what you get when you set the little switches inside the tstat? I always wondered what that controlled.

    So can you speed up the steam entering the rads so they get fully hot as quickly as possible before satisfying the tstat? How fast should they heat? Too fast might cause issues right?
  • crash2009
    crash2009 Member Posts: 1,484
    edited November 2010

    Whats the model # of the thermostat?  Lets make sure its set correctly.  Then you can eliminate that as being part of the problem.  They are all different, I know how to set mine, I have helped a couple other people, none that I have helped have had switches to set the cycle per hour. 
  • thermostat turns off too soon

    did you tell us about your main vents?

     make sure you have plenty of main vents, and put the smallest hoffman vents on your rads. that way as steam is racing through the mains with no back-pressure, it won't start to ascend the risers until the main vents have closed.

    after a few weeks you will have a feel for any needed change in the radiator vents. for instance, at the top of a three floor building, some risers may need the extra venting on their topmost radiator to get the steam up there first.

    also of importance is the pressure. high pressure steam seems to "arrive" more slowly than low pressure, so keep the heavy foot off the pressuretrol.--nbc 
  • ceikey
    ceikey Member Posts: 60
    bad memory

    Crash- Sorry I was thinking back to my old honeywell round tstat which had little switches. The new one is a honeywell RTH2300. It can only be set for a minimum of 2 cycles per hour. how does the logic work....will it shorten the heating cycle to fit 2 cycles every hour even if it ends up not needing it because the temp hasn't dropped below the setpoint??? And how is it timed from heat start to next heat start? BTW, I got stuck at work and didn't make it to Mechanical Insulation today, but i'll be sure to mention your name when I go tomorrow.

    NBC- I have a gorton #2 at the end of the dry return. I just got the fittings to add another but I was planning to use the calculator on jpf321's signature to see how much i really need before ordering more vents. I have the pressure set to 0.5 cut in and 1.0 differential. BTW, How can I make sure the g2 is working properly though? I was skimming last night and the heat kicked on so I waited around to see how quickly the steam got to the main vent. I noticed that the nipple to the vent stayed cool and the dry return got hot all the way to the end. Like the steam just passed right by the vent which didn't make sense to me. I thought the steam would go right to the vent pretty quickly once it got to the end of the return.

    Thanks again guys!

  • crash2009
    crash2009 Member Posts: 1,484
    edited December 2010
    unless someone else has a better idea


    Follow the directions on page 12 to adjust your cycles down from 5/hr to 2/hr and run with that for awhile.  You should notice a big difference.  Maybe you are all ready set to 2/hr?

    Page 13 explains that this thermostat will only allow you to have 2 thirty minute cycles per hour.  Thirty minutes is likely not enough time to fill the rads on your system.  I am unable to fill mine in 60 minutes.  So unless someone else has a better idea, I would suggest replacement. 

    Maybe if you could speed up the venting enough,, 2 thirty minute cycles may be enough. 

    On the Gorton #2, mine both get hot when the steam gets to them.  Then they cool off after the cycle.  You might need to troubleshoot your Gorton (s).  I got 1 bad one last winter.  There was no noise inside it when I shook it.  Mine was stuck open.  I think they should clang a bit when you shake em.  When installed I don't hear anything from them.  Feeling them often during a cycle is the only way I know mine are working.

    If you purchase the PVC covers for elbows and T's, remind Mike that you need some tacks.  Get a few extra.
  • ceikey
    ceikey Member Posts: 60
    Set at 2/hr

    already. So the logic is such that the heat will turn off if the time limit of 30mins is reached OR the temp is satisfied. Thats not good. I guess I will replace it. Any recommendations on a new one that will allow 1/hr?

    The gorton does clang if I tap on it. The nipple did get hot so I guess the vent got hot eventually too, but i didn't feel it. I just thought it was weird the steam flew right by the nipple....i figured it would go up the nipple quickly once it got there.

    Thanks for the tip on the covers.
  • rcrit
    rcrit Member Posts: 74
    testing a main vent

    If you think your main vent is stuck closed you can try pulling it off and see if you can blow through it. You want to hold it more or less vertical and blow from beneath it IIRC. That's how I tested mine anyway.

    This is assuming you're brave enough to put your lips on the threads, they can get kinda nasty :-)

    You'll probably need some good-sized pipe wrenches to the vent off too. My vent is rather new, < 1 year, so a couple of 12" wrenches did it for me. The one it replaced required a couple of feet of cheat bar. YMMV.
    I'm just a homeowner that has a steam system, take my advice with a few grains of salt.
  • crash2009
    crash2009 Member Posts: 1,484

    see what they have to say in the controls section.  I don't know what your boiler needs.  I am just using an old round honeywell set to 1.2/hr.  I needed a magnifying glass to see the 1.2 They musta had good eyes in the olden days.

    Did Steamhead recomend how many vents to put on?
  • ceikey
    ceikey Member Posts: 60
    the gorton is brand new

    I just put it on in Sept. I'll take a closer look next time the heat cycles on.

    I was thinking about the tstat more....i don't think it shuts off in 30 mins regardless of the temp. I had it setback to 62 at night for a while and it ran longer than 30 mins to get the temp back to 70 in the morning. I keep the setback to 66 now after reading the other posts on the subject.

    I have not gotten any recommendations on main vent size. i'm gonna go measure everything right now and post it in case anyone has a recommendation. Be right back....
  • ceikey
    ceikey Member Posts: 60
    main vent capacity

    OK, here's the measurements from boiler to end of dry return....

    2 1/2" - 43"

    2" - 64"

    1 1/2" - 237"

    1 1/4" - 28"

    1" - 402"

    Plugging into jpf321's calculator next....
  • ceikey
    ceikey Member Posts: 60
    jpf are you out there???

    I used your calculator and now i'm trying to understand it....

    I put all my pipe sizes in to figure the total CF. Then I made one row equal the total CF with a 2 1/2" pipe by faking the total length. I don't understand the 3 columns for pressure (1oz, 2oz and 3oz). Either way it calculates one Gorton D (or #1 if main) is required. I have a gorton #2 on already and was considering getting another or whatever is necessary. This says I don't need it...at ~$50 i'm ready to listen....

    What do you think? Cool spreadsheet by the way...did you make it?
  • crash2009
    crash2009 Member Posts: 1,484
    Venting the mains

    This is how to get multiple main vents on a main only tapped for 1.  JPF's chart tells you the max that you can add to the tapping that you have.  (Main vent manifold size)For example, if you build the antler with 1/2" pipe, installing more than 2 Gortons would be a waste of time because a 1/2" tapping can only vent so much.  You should get, from the website here, Balancing Steam Systems, Using a Venting Capacity Chart, By Gerry Gill and Steve Pajek.  There is a whole page of Main Vent Magic in there. 

    What size is the tapping into the main?
  • ceikey
    ceikey Member Posts: 60
    It is 1/2"

    but I knew it would need to be larger to add more vents. It makes sense since the G2 has a 1/2" connection so eventually you couldn't push enough air through the 1/2" nipple to fully utilize the venting capacity of multiple g2's.

    His chart tells you the total capacity needed for a given cfm desired though.My total CF was 0.715 for the main and dry return. So the vent recommendation was 1 Gorton #1. So with 1 Gorton #2 i should be more than adequate. I guess I'll time it once i get the insulation on and if it seems slow then I can add vents.
  • crash2009
    crash2009 Member Posts: 1,484
    edited December 2010
    Time it ?

    So does that mean you all ready have this ?


    JPF's worksheet was designed based on the data from the chart.  There is some great reading in it. 

    2 G2's will vent at about the same rate as an open 1/2" tapping.  It sounds better if you say it backwards.  A 1/2" tapping will handle 2 G2's.  Because at 2oz CFM, a 1/2' tapping will vent 3.400 CFM, and 2 G2's (1.750 each) will do 3.500 CFM.  You won't actually vent at 3.500 because you are limited by the size of the tapping (3.400) Anyway thats the jist of it!
  • jpf321
    jpf321 Member Posts: 1,568
    0.715CFM in what timing?

    how many minutes to vent had you entered for that 0.715 CFM value?

    and also .. double check, I may have logic in there as to whether you have selected RAD-TYPE = MAIN of not .. if rad-type does not = main, it *may* max out at 1 piece #1. So on that "fake row" make sure you have chosen "MAIN" as the rad-type.

    yes I made the sheet and I did learn a bunch in its creation, I think that Excel is one of the best pieces of software ever developed (with Photoshop as a close 2nd). Mind you, there are people that run circles around me in both applications .. well more like drive Lamborghini's in circles around me.

    I'm happy to help with the spreadsheet, but mainly it is simply a calculator based entirely on the Gerry Gill paper. Gerry and I did identify a few bugs with some of the values a few weeks ago, but it's a front end calculator to his paper.

    If you (or anyone) find that by doing the calculations manually, it yields a different result from the spreadsheet, please let me know ASAP and I will look into it.

    BTW, *YOU* control the "minutes to vent" and basically you can really make any row = any vent type based on this "arbitrary number" which *YOU* enter in that field and honestly, I never really understood how exactly to derive that number, since it's real-world impossible to vent a 55ft x 2" main in 1min (I think).

    I always look at 1oz pressure column, I figure that most of the time that I need the venting to do its job I am 1oz or under (at least in residential).

    1-pipe Homeowner - Queens, NYC

    NEW: SlantFin Intrepid TR-30 + Tankless + Riello 40-F5 @ 0.85gph | OLD: Fitzgibbons 402 boiler + Beckett "SR" Oil Gun @ 1.75gph

    installed: 0-20oz/si gauge | vaporstat | hour-meter | gortons on all rads | 1pc G#2 + 1pc G#1 on each of 2 mains

    Connected EDR load: 371 sf venting load: 2.95cfm vent capacity: 4.62cfm
    my NEW system pics | my OLD system pics
  • ceikey
    ceikey Member Posts: 60

    it finally clicked about the pressure column with your last sentence jpf! Thanks!

    I did put in 1min but I understand that is unrealistic. I was surprised at how small a vent it said I needed and it would have been even smaller if I increased the time.

    Crash - I don't have the booklet, but it sounds like I should. Thanks for the explanation. I'm still going to wait until I insulate because it seems like I have plenty of venting based on the calculator. I haven't made it to mechanical insulation yet...keep getting stuck at work late this week.

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