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Boiler keeps cycling on and off

JeuneJeune Member Posts: 6
I am very new to paying attention to my boiler, so I apologize about what I think may be a very easy question to answer. I recently replaced all of my valves with the Gorton valves and have noticed a significant diference in our heat. Set up thermostat for boiler to cycle once an hour and had our boiler cleaned (I am assuming it was cleaned correctly). My boiler is cycling way too often and cannot figure out why. Was hoping someone could help. Thanks so much!


  • KSKI3718KSKI3718 Member Posts: 4
    Thermostat as boiler timer?

    Your thermostat only asks the boiler for heat when the room temperature drops below what the thermostat is set for.  How do you set the thermostat to cycle the boiler once an hour?  Also how often is the boiler cycling,  and did you replace all the vents with the same size as was on each radiator before?
  • AlexRAlexR Member Posts: 61
    other important question

    Is the boiler cycling when the thermostat first calls for heat (eg, before the radiators are hot), or at the end of the cycle (when the radiators are hot all the way across)?  Cycling early is often a venting problem you can correct.  Cycling late is often an oversized boiler that you can't correct.

  • JeuneJeune Member Posts: 6
    Boiler keeps cycling on and off pt.2

    Ok, this is the problem with the cycling. Whenever it shuts off for about 15 seconds the site glass empties and when it starts back up, the site glass fills up 1/4-1/2. I tried to add water manually, but that has not resolved the issue. It will run continuosly for about 7 minutes and shut down until it refills with water. This has to be a terribly inefficient use of gas. Thanks for any help you can provide. 
  • Jason QuinnJason Quinn Member Posts: 95
    Main vents?

    Do you have main vents? The boiler could be cycling on/off because it's reaching its cut-out pressure set on the pressuretrol. With properly sized and installed main vents, air is vented from the system piping allowing steam to efficiently reach the radiators. If the air cannot escape, the steam cannot move which creates an increase in system pressure causing the pressure safety controls to shut off the boiler. When the boiler cycles off, the system pressure drops and the boiler will cycle back on with a call for heat.
  • Jason QuinnJason Quinn Member Posts: 95
    Low water

    If you have wet returns, perhaps they may be clogged. This does not allow the steam that has condensed back to water to return fast enough and fill the boiler. The low water cutoff safety device which protects your boiler from dry firing may be cycling your boiler on/off to protect it.
  • crash2009crash2009 Member Posts: 1,484

    Hi Jeune,  I don't really have an answer for you, but I do have a few suggestions that may help you get a solution.  Could you post some pictures.  One, of the thermostat, one, of the radiators with the new Gorton vent.  Also, post a couple pics of the boiler.  We need to see how the boiler hooks up to the pipes in the ceiling, how the boiler hooks up to the pipes near the floor, and of course a good shot of the side of the boiler with the sight glass on it.

    To post pictures, See where it says File Attachment?  Click on Browse, then go to the place where you keep your pictures, then click on the picture you want to post.  If you want to add some more, click on the Add Another File button. 

    Just out of curiosity, have you called the person that cleaned your boiler and asked them for an explaination of why your sight glass is doing what it does?  
  • JeuneJeune Member Posts: 6
    Cycling Follow Up/w pictures

    First off a;; to everyone who responds thank you, I really, really appreciate it. Just to answer a few questions, KSK, I replaced all valves with Gorton valves per their room by room diagram; Alex, the boiler cycles (cuts on and off) many times before the thermostat reaches its targeted temperature.Jason, we have a Gorton main vent (pictured) and Crash, the person we had clean the boiler has been unreachable for 6 weeks. Crash, I enclosed the pictures you requested I hope this helps. Does this cycling issue hurt the boiler and does it use more gas as well by cycling on and off so much? Thanks to all for your help!!
  • short-cycling after cleaning

    much as i like gorton vents, i disagree with their diagram of vent placement.

    my preference is to over-vent the mains, and put smaller vents on the radiators. as the system is tuned, it may still be necessary to increase the venting of some radiators, such as those on an upper floor where the air in the riser, and radiator has to be handled by the radiator vent on its own. can't see what type of gorton you have, or its location, but i would increase your main venting for a start. a good low-pressure gauge [ psi] makes it possible to see the back-pressure of venting which should be 2 ounces/square inch or less. this gauge would also show you when the system was cycling on pressure.

    you could use a few jumper wires with alligator clips to :

    1.short the thermostat connection to make the boiler fire continuously.

    2.short out the pressuretrol contacts to see whether the short-cycling comes from that.

    3.if not then watch the lwco and see if you have a waterline problem which cuts the burner off [don't do any shorting out on this!].

    the key is observation, and process of elimination to see which control is responsible.--nbc
  • crash2009crash2009 Member Posts: 1,484
    Slow return?

    Jason allready suggested it, I think you have a slow wet return as well.  I marked your picture to show you what that is and where to find it.  The wet return is labeled with a #1.  While we are down there #2 is your Hartford loop.  #3 is how the water gets back to your boiler.

    One way or another you are going to have to find a new boiler repair person.  Try the Find a Contractor button at the top of the page.  Just out of curiosity, what state and or county are you in?  Maybe someone here can recomend someone close to you. 
  • JeuneJeune Member Posts: 6
    Boiler Cycling Issue

    Chicago, Il-Cook County. Is resolving the issue a big deal? Thanks so much, you have been very helpful.
  • crash2009crash2009 Member Posts: 1,484
    Fixing it

    likely would not be that difficult.  The hard part is figuring out exactly whats wrong.  By the way, what is leaking back there against the wall?  (I see the floor is wet)
  • crash2009crash2009 Member Posts: 1,484
    Give Dave a call

    Contact Information

    David Bunnell [email protected] Phone 1-877- 567-7070
  • JeuneJeune Member Posts: 6
    Water Behind Boiler

    Don't know. I noticed it when I was taking the pictures, but I could not find the origin of the water.
  • crash2009crash2009 Member Posts: 1,484
    Can you

    get another picture of what this copper line connects to?  the line I have highlighted in blue.
  • AbracadabraAbracadabra Member Posts: 1,939

    might want to cover up that asbestos insulation
  • JeuneJeune Member Posts: 6
    Copper Line

    Crash, this line leads to the fireplace. Do you still want to see a picture? 
  • crash2009crash2009 Member Posts: 1,484
    Copper gas line

    Oh, is that copper line for gas to the fireplace?  I thought it might be a water line.  So much for that idea. 

    If possible, it would still be nice to have a peek back there.  Somebody here might spot something that could help you.
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