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Steam Heat Short Cycling

Last year, we moved into a new house with a steam boiler system. We accidentally overfilled the boiler resulting in exceptionally filthy water and major sight glass surging and horrible noises. Shortly after, short cycling began. Whenever there was an automatic call for heat, the boiler would fire for 5-7 minutes and turn off. Like clockwork. The only thing that stopped the short cycle is manually increasing the temp from what it’s set to or turning off the heat. Nobody could figure out the issue; we replaced the pressuretrol, gauge, and thermostat and the short cycling continued. We also ensured the boiler was properly sized. Finally, we replaced the LWCO and the short cycling stopped! I guess the sensor was corroded. Well, this year we had our boiler maintenanced. Shortly after, extremely dirty water and intensely surging sight glass followed and then short cycling again after every auto call for heat. Exact same problem as last year. Our maintenance guy has replaced the thermostat four times to no avail. Should we replace low water cut off again?
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Comments

  • Jamie Hall
    Jamie Hall Member Posts: 23,272
    Sounds like you need someone who actually knows steam heat. Changing the thermostat won't make a bit of difference, and it's not too likely that changing the low water cutoff would either.

    What will make a difference is figuring out why the boiler is surging so badly. In general, even in bigger boilers the water level while steaming doesn't rise and fall much more than an inch or so, and usually less.

    Do you know what was done for maintenance on the boiler? Just for starters at this point, I would be inclined to drain the boiler completely and refill it with fresh water (while it's off and cold, please!). Then I would bring it up to a nice boiler for about five minutes. Then I would skim it for a few hours, though in an older boiler that shouldn't be needed but it won't hurt.

    Fill it to where it needs to be, and try running it.

    No chemicals. No cleaners. Nothing but good fresh water.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • BobC
    BobC Member Posts: 5,477
    Take the LWCO probe out and clean it, it could be fowled with oild gunk in the boiler.

    I would give that boiler a good flushing to get rid of as much crap as possible. Then a good skimming might be in order. Boiler techs are loathe to do this because proper skiming but as long as you have a skimming port he can show you how to do it.

    Bob
    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,512
    @AshlynDL

    Sadly, we are in an era of substandard contractors and technicians who in many case know little to nothing about steam.

    When the "technician" starts randomly changing parts (shooting the parts cannon at the boiler)

    It's a big clue that they don't have a clue


    If you post the city you are located in someone on this forum may have a recommendation. And you can try "find a contractor" on this site
  • AshlynDL
    AshlynDL Member Posts: 32
    Thank you all for your insight. The surging has stopped. We did skim until the water ran clear. The previous owners left us a note to skim weekly. They said to do a “low water cut off and blow down.” We are so perplexed and frustrated. When the professionals bypass the thermostat, it does not short cycle. It ONLY short cycles when there is an automatic call for heat. If we manually raise it to a higher temp, it will stay on until satisfied. Then, it will short cycle again with the next automatic call for heat. Last year we were told the boiler being overfilled and having all that filth likely damaged the LWCO probe and so it was tripping the system when there was an automatic call for heat. I’m tempted to have that replaced again (because it was surging filthy water and overfilled AGAIN this year). BUT last year and this year the LWCO would properly function when we tested it by lowering the water level. This is terrible :( So far tonight we are at:
    3:23 on 3:27 off

    3:51 on 3:56 off

    4:16 on 4:20 off 

    4:31 on 4:34 off

    Heat doesn’t even make it to the radiators in that time span. 

  • JUGHNE
    JUGHNE Member Posts: 11,058
    What do you have for a thermostat?
    Do you have the install book for it? If so look for the installer set up for cycles per hour or type of system... they come out of the box set up for forced air.
    You want 1 cycle per hour or the steam/hot water/radiant setting if those are your choices.

    Also you may have a "Cycleguard" LWCO which will shut down the boiler every 15 minutes or so for 90 seconds. Sometimes this is a problem.
    wlgann
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,512
    I think @JUGHNE may be on to something. If when they bypass the thermostat the boiler runs but short cycles when on a normal call for heat I would be suspicious of the thermostat.

    On the other hand, If you can make it short cycle while the tech is there they should be able to find what control is short cycling the boiler

    I think you need a new contractor as I posted above
  • AshlynDL
    AshlynDL Member Posts: 32
    These are three of the thermostats we have tried (all installed by professionals). The odd thing is, none of the programming would have been changed after we bought the house. And it  didn’t short cycle initially. Last year when the tech was here to witness the short cycle, it didn’t stop until replacement of LWCO. Perhaps I will ask them to be sure it’s set to one cycle per hour?
  • AshlynDL
    AshlynDL Member Posts: 32

  • AshlynDL
    AshlynDL Member Posts: 32
    Ours says this... 
  • JUGHNE
    JUGHNE Member Posts: 11,058
    Do you have the Cyclegard on the boiler now?
    Was the Safegard the old one...previous to the Cyclegard?

    If you can find the info on the tstat and look for the installer set up guide, you could see what you currently have.

    This could avoid a call back you may have to pay for.

    If the same "Pros" installed 3 stats and never set it up for steam, and you mention it you might get the "deer in headlights" look from them.
    And probably a service call fee if they "fix" it for you.

    LWCO's have a probe that needs cleaned every couple of years.
    You have to drain the water down below the probe to remove and clean.
    That is actually beneficial to a dirty system.

    Did they clean the pigtail under the control?
    The boiler may need more skimming, what is your procedure for skimming?

    How about some pictures of boiler and piping, floor to ceiling all sides?

  • AshlynDL
    AshlynDL Member Posts: 32
    Thanks for your patience. So, the previous owners left a note for us to skim weekly (they called it a low water cut off blow down). We didn’t do that all last year or this year because we were told doing that weekly is ridiculous and adds too much oxygen to the boiler via new water. But last year they think the build up of sludge tripped the LWCO. They Replaced it, short cycle stopped immediately. This year maintenance did NOT skim. They said the new LWCO was covered in Sludge and cleaned it. I KNOW they did not drain water below probe when they cleaned. Very intriguing that the model we have on now says it intermittent tests every 20 mins and we are on just about every 20 mins for five mins or less. We will check tstat set up, though they assured us it was programmed properly. Also, we never changed the programming when we FIRST started short cycling last year. The only varying factor (last year and this) was the crazy surging and filthy not skimmed water leading to replacement of LWCO due to short cycling. Unsure why the stat would randomly pose a problem? I will post pics of everything shortly! 
  • Jamie Hall
    Jamie Hall Member Posts: 23,272
    A low water cutoff blowdown is only applicable to float type LWCOs. It is not needed for a probe type LWCO -- and it is certainly not the same thing as a skim, by a long long way.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • AshlynDL
    AshlynDL Member Posts: 32
    This is how we looked last year and this year right before short cycling started...
  • neilc
    neilc Member Posts: 2,700
    AshlynDL said:


    does that label say
    "Remove this label" ?
    known to beat dead horses
  • AshlynDL
    AshlynDL Member Posts: 32

  • AshlynDL
    AshlynDL Member Posts: 32
    We are now turning on every 3-5 minutes. 7:01 on - 7:04 off and now on again at 7:09. This is CRAZY. We have to let it short cycle all night to ensure it’s doing it when the guy arrives tomorrow. 
  • neilc
    neilc Member Posts: 2,700
    let's talk about main venting,
    what do you have for main venting?
    known to beat dead horses
  • AshlynDL
    AshlynDL Member Posts: 32
    I’m feeling more and more convinced it’s that Intermittent Test with the LWCO??? It would make sense why the firing in and off is so predictable time-wise. Would make sense why that solved the problem last year. Here is the main...
  • AshlynDL
    AshlynDL Member Posts: 32

  • neilc
    neilc Member Posts: 2,700
    that intermittent test is every 20 minutes, right?
    you're cycling at 4, 5, 6, and 7, it's something else,
    like your Ptrol shutting off on pressure, cause that main vent is too small, and system is , pressurizing,
    what does the gage read when it shut down ?
    anyone with a meter ought to be able to figure out what's turning off there,

    How long is your main ?
    and can we see a more distant view of that vent, showing the main and what happens both before and past the main vent?
    the main doesn't loop around on itself, does it?

    looking at the boiler picture, that LWCO is mounted very close to the water line,
    where's the water level in the glass when she shuts down? and the pressure ?

    known to beat dead horses
    ethicalpaul
  • AshlynDL
    AshlynDL Member Posts: 32
    I recorded *most* of the cycles tonight before we turned off:
    3:23 on 3:27 off
    3:51 on 3:56 off
    4:16 on 4:20 off
    left the house 
    7:01 on - 7:06 off
    7:09 on - 7:14 off
    7:19 on - 7:25 off 

    Minimal pressure builds up, if any for the duration of the cycle, be it a regular length or short cycle. 

    Water remains mid sight glass when on. Again, this system was “fixed” and working beautifully the remainder of the heating season after low water cut off replacement.  

    Temp has gotten colder tonight, auto call for heat is more frequent (I believe it is .5 differential from display temp when it calls for heat), it turns on and shuts off every time unless we manually increase what temp is set to. 

    Main does not loop around itself. 
  • neilc
    neilc Member Posts: 2,700
    so an under vented main will cycle at the Ptrol, but forget that for a minute,

    are the thermostat wires tight at both ends?
    nothing loose and barely holding on?
    broken wire in the wall, making intermittently?

    if you jump the wire at the thermostat, does it cycle?
    same at the boiler, jump the thermostat wire, does it cycle?
    meter the Ptrol and see if it's doing its job, and cycling.

    "Minimal pressure builds up, if any for the duration of the cycle"
    this sounds like a Ptrol doing its job
    known to beat dead horses
  • AshlynDL
    AshlynDL Member Posts: 32
    Brand new wiring to the stat today - prof thought that would remedy the issue. It did not. 

    “If you jump the wire at the thermostat, does it cycle?
    same at the boiler, jump the thermostat wire, does it cycle?” 

    Could you clarify that?

    We have had four thermostats in the last two weeks and the same problem remains. It seems that’s not it?
  • neilc
    neilc Member Posts: 2,700
    if you take the thermostat out of the equation,
    and jumper the wire at the boiler so the boiler runs,
    the boiler will cycle on the Ptrol settings, I think that's what you're seeing,

    since you pulled new wire, the "broken intermittent" in the wall is so much less likely that we won't bother jumpering at the thermostat base,

    the thermostat should only turn the system off when temperature setting is met,
    you're sure the stat(s) is set for steam, or hot water?

    the boiler cycling on the Ptrol settings is a common issue here when boilers are over sized compared to their connected load, the radiator EDR,
    and, or,
    when there is undersized main venting, and the mains don't clear their air,
    then radiators have to do the extra work of venting both main, and radiator air,
    if you're not warm, then radiator venting, and or traps, need be discussed,
    one pipe rads? or 2 pipe?
    known to beat dead horses
  • Jamie Hall
    Jamie Hall Member Posts: 23,272
    What @neilc is asking is what happens if you connect the two thermostat wires together at the boiler. Does it still cycle like that? If it does, it's not the thermostat. If it doesn't -- it's most likely the thermostat or the wires leading to it.

    You really need someone who knows steam boilers and there controls and who has a multimeter and knows how to use it to find out which control is shutting off the boiler. It's not that hard.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • AshlynDL
    AshlynDL Member Posts: 32
    One pipe radiators. Again, the system worked wonderfully; if it was oversized, wouldn’t this short cycling have been a consistent problem? I believe when thermostat is bypassed it doesn’t short cycle - not positive, but I think that’s what they tested. Have had two different guys here nobody can figure it out. Except last year when they trial and error replaced LWCO and it stopped short cycling. 
  • AshlynDL
    AshlynDL Member Posts: 32
    They said thermostats are correctly set.
  • neilc
    neilc Member Posts: 2,700
    maybe when you flooded that main vent took a hit, and isn't venting now or well?
    when the boiler first starts making steam, do you hear hissing / airflow / anything at that vent?
    known to beat dead horses
  • AshlynDL
    AshlynDL Member Posts: 32
    No noticeable noise at all from that vent!
  • neilc
    neilc Member Posts: 2,700
    ok, same question, with the back of your hand, do you feel anything at the vent hole?
    or if you touch it, does it get steam hot?
    be careful, steam is really hot,
    known to beat dead horses
  • AshlynDL
    AshlynDL Member Posts: 32
    I will test this first thing in the morning. We just turned the heat off so it doesn’t turn on and off all night long. Thank you SO much for your help. 
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,512
    just need a service tech that has a clue. finding out what control is shutting this thing down shouldnt be such an issue
  • AshlynDL
    AshlynDL Member Posts: 32
    Here’s hoping. We are 0/3 so far. Coming back today to hopefully remedy this. Will keep everyone posted. Your help and insight is extremely appreciated. I have passed along your suggestions.
  • AshlynDL
    AshlynDL Member Posts: 32
    edited November 2021
    Continued insistence that it’s the thermostat by the prof. Does it matter that we have 5 thermostats sitting on our table? Does it matter that last year after replacing the LWCO things worked perfectly? I’m ready to rip out this system and convert to forced heat! The challenge is, the short cycling doesn’t always happen when they are here so they can’t just sit and wait for it to happen. 
  • neilc
    neilc Member Posts: 2,700
    known to beat dead horses
  • neilc
    neilc Member Posts: 2,700
    that's a radiator vent, 1/4 inch, it probably got jambed when you flooded and is not working,

    you need a real main vent, 3/4 or 1/2, maybe more than 1 vent, pipe length matters,
    https://www.supplyhouse.com/Hoffman-401434-75-1-2-x-3-4-Straight-Steam-Main-Air-Valve-8038000-p
    lose the upper reducer and maybe change the length of that nipple,

    are the vents on the radiators all working? hiss or passing air, getting steam hot?
    AshlynDL said:


    known to beat dead horses
    shyheim
  • Jamie Hall
    Jamie Hall Member Posts: 23,272
    You seem to have quite the string of incompetent people looking at your system. None of whom appear to have made a useful effort to find out which of at least three controls is turning off your boiler -- or if there is a wiring problem.

    Never mind the vent for the moment. You do need a bigger one, and it may be in the wrong place -- but you first need to solve your control problem.

    There must be someone in your community who actually owns a multimeter and has some idea as to how to use it. He or she might also be able to look at the wiring and figure out how things are connected. Then, he or she should be able to find out which control is opening the circuit and thus turning off the boiler. Have them come here, if necessary to figure out what things are.

    And stop fixating on the thermostat or the LWCO. Find what is really the problem.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,512
    I can't help anymore.

    I don't know why you don't use "find a contractor" on this site and/or post the city you live in.

    Someone on here may have a recommendation of someone who can actually fix this
  • AshlynDL
    AshlynDL Member Posts: 32
    Schenectady, NY
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,512
    edited November 2021
    Not a good location. We have had plenty of people on this forum looking for contractors in that area with not very good results.

    There was a fellow on here, haven't seen him in a while @SteamingatMohawk that I think was up that way, not sure if he was a contractor or a talented homeowner

    Maybe @Jamie Hall will remember