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Need Input: Balancing Quirky System

cnjamroscnjamros Posts: 71Member
edited November 2018 in Strictly Steam

Hi there, everyone.

I'm sorry to revive this old topic, but after reading the many posts on it in the past my brain is melting... plus tech may have changed in recent years, so here we go:

I am looking for a steam-worthy thermostat that will primarily prevent overshoot. I see many posts about the modern "feature" of no anticipator, in favor of CPH settings. My boiler is appropriately-sized for the house (miracle) and I don't, as of yet, have a problem with cycling.

Downstairs is well-radiated. Upstairs slightly less so, and therefore always a little cooler. Mains are well-vented and also mostly insulated (runouts are not yet insulated).

Right now, the basic digital thermostat that I have will overshoot by 2-3 degrees, though the stat is in a stair alcove with one of the larger radiators.

Basically, searching for a stat that will learn, or that I can set, to give my well-insulated house the little puff of steam that it needs to maintain temp without wild temp swings.

Thanks in advance for your thoughts!


  • KC_JonesKC_Jones Posts: 4,075Member
    What brand and model do you have now? Are you sure your particular thermostat is set up correctly to work with steam? If not might be worth checking before buying new.

    Of course it might not have that capability. Many of us use and like the Honeywell VisionPro 8000 series.
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
  • The location of the thermostat is important as well, and the Honeywell VisionPro series supports a remote sensor, which could be placed in a more opportune location in the house.
    Keeping the pressure down will reduce the radiator temperature, and aid comfort as well.—NBC
  • Jamie HallJamie Hall Posts: 10,179Member
    The modern "feature" of no anticipator is no feature at all -- but unfortunately, if you want the rest of the modern bells and whistles (like programming), you're stuck. As the above folks have said, a properly set up VisionPro is about as good as it gets.

    Of course, if you have an old mercury T87 around, and don't need programming, that has the anticipator -- and if you get that set right, it won't overshoot.

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • cnjamroscnjamros Posts: 71Member
    Thanks everyone. @KC_Jones, I currently have a Honeywell RTH2300 installed. Very basic unit.
  • KC_JonesKC_Jones Posts: 4,075Member
    You can set cycles per hour on that one, but only down to 2. It would probably be worth seeing where you are set to as the default could be 5 which would not be very good for steam.

    See the manual in the below link, start on page 11 to get into settings then page 14 for that particular setting. I'd try that before changing the thermostat.

    If that doesn't help then go for a new thermostat. The VisionPro has much more control and has a learning function that allows it to learn the reaction time of your system. It's not perfect, but may be better than what you have.

    Does it overshoot all the time or only on a recovery?
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
  • cnjamroscnjamros Posts: 71Member
    Gotcha. I'll double check the CPH setting. It had been overshooting all the time. To compensate, I've tried setting the temperature 1 degree cooler to 71... however, that change was accompanied by some pretty mild weather. I've had less overshoot, but the ambient indoor temperature has naturally been hovering around 71 anyway... so hard to tell if anything has changed as of now.
  • FredFred Posts: 7,776Member
    Is the temp over shooting throughout the house or just in the alcove where the thermostat and the large radiator are located? Are you using a thermometer and checking the temp in other parts of the house? It could be as simple as moving the thermostat further away from that large radiator which I'm sure puts a lot of residual heat out in what sounds like a small area. That situation may also create a wider temp swing in other parts of the house.
  • cnjamroscnjamros Posts: 71Member
    Hi everyone.

    I have a Vision Pro 8000 on order with 2 remote sensors, one for upstairs and one for downstairs.

    I'm also down-venting the 1st floor radiators from MO'M 6 to 5's or 4's. Upstairs radiators with C's and D's, in hopes of getting all radiators to fill at the same time, or upstairs slightly sooner. When I did the full analysis of my system, the math suggested 6's for all... so I'm balancing out from there.

    I will let everyone know what happens. thanks for all the input!
  • cnjamroscnjamros Posts: 71Member
    edited November 2018
    Ok, I have installed the VisionPro with one sensor in a sensible location downstairs, and the other in the Master upstairs. Set for an average temp of 71 degrees, and CPH set to 2.

    Here's the good news: the system is quiet as a churchmouse. I barely can tell that it's on, but I never see the temperature on the thermostat display vary from 71 degrees.

    Here's where there's room for improvement: The upstairs bedrooms are still a few degrees cooler than the downstairs.

    I realize there will be some differential always because there are fewer radiators upstairs and it's not as well insulated. BUT because the VisionPro is being so efficient at maintaining temperature, the boiler doesn't run long enough to get the upstairs rads more than lukewarm.

    I got to thinking that if I set the CPH to 1, the boiler might run enough for the upstairs rads to get hot... which might create more temperature swing overall, but would at least get some more heat up there.

    I made the CPH change, and the upstairs did indeed get warm. But now the boiler runs long enough that the upstairs Master radiator, and one radiator downstairs in the Front Room are hissing significantly.

    I'm caught between venting my rads as slowly as possible, getting heat upstairs sooner to compensate for under-radiation, and getting everything to fill before too much pressure builds up and the hissing begins.

    I'm attaching a diagram of my system for reference, with some notes of its idiosyncrasies:

    -Mains are insulated
    -Near-Boiler Piping seems ok (photo attached)
    -A small amount of bounce in the sight glass when running due to no skim port/no skimming since install in 2011. (video here:

    -Pressuretrol set to C/I: .5, Diff:1
    - When I started to balance, I had MOM#6s on every rad, because the math seemed to point to that (perhaps I screwed this up?)
    - After moving in, the first thing I did was vent the mains with G#2s. Despite the math, the short main fills in 1:30 (yes!) and the long main filled in 4:30 (hmm?). Thought my rads were stealing steam, so I lowered most rads on this leg to MOM#4. Long main now fills in 3:30. **Perhaps I should REDUCE venting on my shorter main to help equalize them???
    - 2nd Floor Bathroom is the hugest rad in the place. Column instead of tube, so it needs a LOT of steam to fill. I tried venting this to get it to fill with the others, but it was panting/gurgling, so it's back to a MOM#6 and resigned myself to the fact that it won't always fill completely.
    - Front Room radiator always seems to be a hisser. Perhaps increase this to a MOM#6?
    - BIGGEST ISSUE: 2nd Floor Master Bedroom *always* seems to be the last to fill, but also needs heat first (or at least at the same time) to compensate for under-radiation. Currently have a MOM#D on this. It's heating, but getting significant hiss and whistling (not popular at night)

    Anyway, my situation is by no means dire... but I would really like to even it out as much as possible, get enough heat upstairs, and get rid of the noise.

    If anyone has insight based on my notes and the attached diagram, I would be thrilled to hear them.


  • Gary SmithGary Smith Posts: 269Member
    I would increase the venting on the long main, maybe add another G2, and then experiment by decreasing the vent speed on the radiators on the first floor. I've found that decreasing the venting on hot areas works way better than trying to increase the venting on cool area radiators. I particularly like the Ventrite #1 adjustable vents for radiators as they make slight adjustments really easy.
  • Panting and gurgling may indicate a low spot which is trapping water, and interfering with the steam arrival.
    Put some more main venting on, such as a big mouth, along with a low pressure 0-3 psi gauge, as the pressuretrols are often not accurate.--NBC
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