boiler keeps going off/on, off/on....help!

Discussion in 'Boiler Forum' started by TonyV53, Dec 6, 2009.

  1. TonyV53

    TonyV53 New Member

    Messages:
    12
    Location:
    Hamden, CT
    I just moved into my first house. 1950 Colonial with an old Stewart Warner boiler which uses oil, with hot water radiators of course. I first had a problem with the safety relief valve but resolved that by draining my water logged expansion tank.
    Now I've notice a much bigger problem. My boiler will go on for about 4-5 mins, then turn off for 3-4 mins. The thermostat is set to 68 and its reading a current temp of 55 so its shutting off way before reaching desired temps.
    On the boiler it reads around 12-15 psi when it turns off, which I understand is good, but the temp is 190 and it seems to go off when it starts going over 190. What am I missing?? Is there a valve not opened.

    What am I missing, and how do I fix it?
    Also, what should be my low/hi aquastat setting for this brand boiler?
    Any help is appreciated. Please keep in mind this is my first home and first boiler I've ever had to try and fix so please excuse ignorance.
    TonyV53
  2. nhmaster

    nhmaster Master Plumber

    Messages:
    3,189
    Location:
    S. Maine
    It's not circulation. Probably the circulator is bad or you have a lot of air in the system. Since you opened it up to change the tank I would go with a lot of air first.
  3. TonyV53

    TonyV53 New Member

    Messages:
    12
    Location:
    Hamden, CT
    So what should I do to try and get the air out of the system. Should I bleed the radiators? There is no way to do it off of the expansion tank, I looked.
  4. msgale

    msgale New Member

    Messages:
    90
    Location:
    Ohio
    yes, bleed every radiator. If air is the problem, you will find a lot of it in them.
    if you don't get a lot of air out, then you have another problem.

    the boiler properly shuts itself off since the water is too hot. Once the water hits 190, you dont want it heated anymore. Your challenge is to find out why no new cooler water isnt being supplied to the boiler, and the hotter water pumped out to your radiators
  5. TonyV53

    TonyV53 New Member

    Messages:
    12
    Location:
    Hamden, CT
    Got it.. Thanks a LOT. I'll do that and
    check back to tell you how I made out, thanks again.
  6. Doherty Plumbing

    Doherty Plumbing Journeyman & Gas Fitter

    Messages:
    810
    Location:
    Penticton, BC
    The boiler is tripping on it's high limit because of lack of water flow. Could be air, could be a bad pump, could be a pump that has a clogged up impeller, could be a valve closed.

    you need to:

    1. Make sure all valves are open.
    2. Make sure the pump is on and running.
    3. Bleed your rads
    4. Possibly pull the pump and inspect it further.
  7. TonyV53

    TonyV53 New Member

    Messages:
    12
    Location:
    Hamden, CT
    Ok, I drained each radiator. Each of them had about 1 sec of air in them which
    doesn't seem like a lot. I monitored the boiler it shut down again. This time got up to about 205 w/15 psi. The radiators are hot so I know the hot water is
    circulating to some extent.
    One thing to mention but I don't know if it really matters. I have 2 of the 12 total radiators cut off from the system. I found that they were cracked so I install shut off valves to one and the other I removed and just capped the 2 pipes.
    Also, the thermostat doesn't seem to be reading the current correct temp. It's says it's 57 but I have a thermometer next to it that reads 47. I don't know if any of this is relivant.
  8. TonyV53

    TonyV53 New Member

    Messages:
    12
    Location:
    Hamden, CT
    Rads are bleed and all valves are open, so trying to determine what the problem is with thr cirulator now, thanks!
  9. Doherty Plumbing

    Doherty Plumbing Journeyman & Gas Fitter

    Messages:
    810
    Location:
    Penticton, BC
    Has the system worked properly since you removed those 2 rads from the system? Depending on how it's piped this might be problem.
  10. msgale

    msgale New Member

    Messages:
    90
    Location:
    Ohio
    one sec of air is nothing, either the air block is some trapped elsewhere, or it's not an air problem.

    Radiator capped off: did this immediately precede the circulation problem? normally they are in parallel, but if you happen to have a series piped system, you may have shut it all down.
  11. TonyV53

    TonyV53 New Member

    Messages:
    12
    Location:
    Hamden, CT
    I don't know if the system ever worked correctly. I just bought the house 3 weeks ago. When my boiler tech came over to service the boiler we then turned on and noticed rite away water coming from kitchen rad. I sent him home so I wouldn't get my billed racked up.
    He had replaced a part which I can't remember the name of, but it's that safety eye that looks into the boiler and shuts down if it doesn't see light within 30secs. That cost me $350.
    Anyway I installed shut off values in the basement going to that kitchen rad, only to find out one of the rads on 2nd fl master also had crack, so instead of installing shut off valves everywhere I decided to just cap that one until I can find replacements and get heat to rest of house before low temps start hitting 30's and I have a bigger problem.

    So short answer is I don't know because it wasnt working long enough for me to monitor it.
  12. nhmaster

    nhmaster Master Plumber

    Messages:
    3,189
    Location:
    S. Maine
    Well lets start with how it should be running

    The aquastat controls the maximum temperature the boiler will reach. Called the high limit this control is usually set between 180 and 200 degrees with a 10 degree differential which is how many degrees the boiler will drop before the control operates again. When high limit is reached, the burners shuts off. during normal operation the boiler will come up to limit.

    You may or may not have a low limit also. This sets the temperature that the boiler reaches before the circulator pumps will operate. It's purpose is to maintain temperature in the boiler if you have a tankless coil for domestic hot water.

    You can check circulator operation either by checking for power at the circulator or listening to it. You should hear it run.
  13. rmelo99

    rmelo99 Network Engineer

    Messages:
    349
    Location:
    Connecticut
    Since you just bought the house 3 weeks ago, and have found some cracked rads tells me you must have purchased a foreclosure/bank owned house with frozen pipe damage.

    Some pics would help us help you better. Since you said radiators many people assume the stand up kind, but being the house is from 1950 are you talking about baseboard kind of radiators?
    If so then it is very possible that they are piped in such a way that you cannot remove/cap any individual unit without affecting the rest of the system.

    Bring us some pics or a better description of how the piping arangement is in the basement.
  14. patsfan78

    patsfan78 Web Development | HVAC

    Messages:
    33
    Location:
    Maine
    Post a couple pictures of the radiators themselves. If they are the baseboard type radiator and/or if they are piped in series, that is a potential problem when removing or turning off water flow to any radiator. We need to determine if the radiators, whatever type they are, are piped in a series (water must flows through one radiator to the next) or not. They shouldn't be piped this way if they are traditional radiators but it doesn't hurt to double check.

    Just gotta start eliminating variables
  15. TonyV53

    TonyV53 New Member

    Messages:
    12
    Location:
    Hamden, CT
    Yes, it was a forclosure bank owned property and of course they never told me about it if they knew. To boot, my inspector chalked it up as a broken fitting and that I just needed to fix that and I would be all set.

    Anyway, here are some more details about the rads.
    They are framed into the wall, so they only come out about 1 in from the wall with a steel cover. There are vertical 3/8 in piping going into each end of the rads, but 3 to 4 pipes go through the rad from end to end.

    The one rad that I installed shut offs on, come off of a main copper pipe (about 1 1/2 - 2 in copper), so I installed shut off on the 3/8 piping branching off of that main pipe going to that rad.

    Here are some pics of a rad I removed from the kitchecn wall.

    its a Trane rad:
    http://i81.photobucket.com/albums/j221/nasdaq53/trane10.jpg

    from top view:
    http://i81.photobucket.com/albums/j221/nasdaq53/rad10.jpg

    from other end of top view:
    http://i81.photobucket.com/albums/j221/nasdaq53/Trane_Radiator2.jpg

    side view:
    http://i81.photobucket.com/albums/j221/nasdaq53/Trane_Radiator9.jpg

    rad is laying on its side:
    http://i81.photobucket.com/albums/j221/nasdaq53/Trane_Radiator6.jpg

    a side angle:
    http://i81.photobucket.com/albums/j221/nasdaq53/Trane_Radiator4.jpg

    I can take any other pics you want also.
    Thanks again for looking further into this guys.
    Last edited: Dec 7, 2009
  16. Doherty Plumbing

    Doherty Plumbing Journeyman & Gas Fitter

    Messages:
    810
    Location:
    Penticton, BC
    That thing is OOOOLLLLDDDDD.

    Anyway any more info (or pictures of your boiler room) to aid us in helping you solve why your boiler keeps tripping off on it's limit switches.
  17. nhmaster

    nhmaster Master Plumber

    Messages:
    3,189
    Location:
    S. Maine
    Dem ain't radiators dem is convectors and they are always piped paralel off a monoflow tee system.
  18. rmelo99

    rmelo99 Network Engineer

    Messages:
    349
    Location:
    Connecticut
    Some pics of the boiler room piping would help us confirm your piping setup.

    It will also help us to guide you to purge air...could be an air lock in the piping that needs to be purged out of a purge valve in the basement.

    Think of the piping as one big loop with a start(supply) and finish(return). The water has to leave the boiler work its way thru the system and back to the boiler. The circulator moves the water. Sometimes the air blockage is big enough the circulator can't push it through. Need to confirm water is making it's way all the way around before you go looking for bad equipment.

    One zone, multi zone? Any zone valves?
  19. TonyV53

    TonyV53 New Member

    Messages:
    12
    Location:
    Hamden, CT
    Yes, the units are 1950 old. I will try to post some pics of the boiler room tonight but it won't be until later.
    It's one zone, and I have a zone valve coming off the boiler.
    Thanks again,
  20. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,889
    Location:
    New England
    If there's only one zone, why do you need a zone valve? Do you have an indirect WH?
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