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How Often Should Boiler Auto Fill trigger?

dkirkwood Member Posts: 21
Hi, I have a Burnham steam boiler--it was installed about 17 years ago. The system is single pipe. The auto fill triggers nearly every heating cycle--it doesn't add much water each time, but it does trigger to inject some water. It seems to keep the water level at exactly the half-way point in the sight glass.

Is this normal? Should it need to inject a bit of water on each firing cycle? I am certain I do not have any leaks in the pipes; the vents on all radiators are new adjustable ones--i also replaced the main vent.


  • KC_Jones
    KC_Jones Member Posts: 5,542
    Okay there will probably be several opinions on this. First many will tell you the answer is almost never as you should be monitoring the boiler and maintaining the water level yourself, but that doesn't really answer your question.

    You are correct no way should it be activating that often. Can you post some pictures of the feeder and the Low Water Cut Off that controls it. Make sure the pictures show the boiler as well so we can see what the install looks like.

    It's either malfunctioning, set at the wrong level or the water level is indeed dropping dramatically during a cycle.

    If it's the last one that would indicate a slow return, surging, or actual water loss on every cycle. Since you indicate the water level is always correct my suspicion is you are actually losing water.
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
  • SeymourCates
    SeymourCates Member Posts: 162
    If the boiler is maintaining the same water level consistently after each addition of water, clearly you have a leak. It's got nothing to do with the feeder or the LWCO or any other mechanical device. It also has nothing to do with the quality or type of install. The boiler is simply making up the lost water.

    The lost water can either be leaking from a wet return or it can be leaking steam from the vents or the radiator valves. There is no other option.
  • Fred
    Fred Member Posts: 8,541
    If it's a Cyclegard LWCO, it simply may be stopping the heat cycle to check the water level. Are you 100% sure the water feed is actually adding water? If it is, it is likely a leak. Do you have any return pipes under the floor? When the boiler is running, have you gone outside and checked to see if a lot of white smoke is coming out of the chimney?
  • dkirkwood
    dkirkwood Member Posts: 21
    thanks for all the input. I am attaching photos--I have done a ton of work on the house in terms of gut reno--so I am fairly sure there are no outright pipe leaks anywhere--the radiators all have those fast-heat vents, the kind designed to get air out of the system quick--and they are open a good bit--all the radiators are recessed in wall, so i don't see any obvious steam--but do you think that steam escaping could cause such significant loss?

    To answer one question: I am sure it is injecting a bit of water--it sounds as if I hit the add water button on the auto feed for a 1, maybe 2 seconds--it does this 1-3 times a cycle.
  • Fred
    Fred Member Posts: 8,541
    edited December 2017
    1 or 2 seconds isn't a lot of water. It is not normal but it is very possible a vent or two isn't closing or a valve is leaking around the radiator valve stem and needs to be repacked.
  • Alan Welch
    Alan Welch Member Posts: 261
    After 17 years it may well be the boiler itself. Look for white smoke from chimey when running and making steam.
  • Overfilling the boiler up to the header, and letting it sit for a couple of hours will reveal any leaks in the boiler itself.—NBC
  • j a_2
    j a_2 Member Posts: 1,801
    Looks like no isolation valves,on what some call auto feeder...so disconnect it and let the boiler rip, check the water level after a few cycles,would be my opinion...If it using water my guess based on your supplied info is the leak is within the boiler....flood it and get a bright light...17 years old is a boilers mid life and some just don’t make it
  • dkirkwood
    dkirkwood Member Posts: 21
    Hi All, thanks for advice and help. I still have to flood boiler to see if i detect a leak--but here is more information on the actual amount of water loss:

    I marked the site glass before the boiler fired, to record the amount of water in it. Then, 24 hours later made another mark when the boiler was at rest, and had not fired for over 20 minutes.

    I then refilled the boiler to the start point 24 hours earlier, and then drained the water into a pail to the end point--and measured the actual water loss.

    It is about exactly 1 gallon loss in 24 hour period--note, that the water loss depends on how much the boiler runs--a gallon represents the loss when temperatures are <25 degrees outside, and the boiler runs frequently during the period. I do not have loss when the temps are above 45, and the boiler cycles much less

    There are 14 radiators, all with VAAV Varivalve vents--the vents are fairly new, about 1-2 years.

    I have inspected all return lines--none are buried, and I have found no leaks.

    So, I am wondering if the steam is lost thru the VAAV valves--I have noted that the boiler gets steam to the radiators at very low pressure--e.g., .5 -1.5 psi---the pressuretrol rarely cuts the boiler--it is set to cut at 1.5psi

    Does the VAAV vents close based on pressure, or temperature? I am wondering if they never close when steam fills the radiator, because the pressure is low? Or, do they close based on the temperature of the steam?

    Thanks for all the help
  • Fred
    Fred Member Posts: 8,541
    Vents close on steam/temp. Varivalve vents tend to be problematic in that their venting rate is very aggressive. I would check all radiator ventsto make sure they all close when steam hits them, check all supply valves to make sure none of them leak and you don't see any steam escaping around the packing nut and check you main vents to make sure they don't leak and that they close when steam hits them. Also, make sure your system pressure is no greater than 1.5PSI. If you don't have a 0-3 PSI gauge on your boiler, invest in one. The 0-30 PSI gauge is worthless at low pressures.
  • j a_2
    j a_2 Member Posts: 1,801
    Didn’t take the time to read thru previous responses...the auto feeders as it’s called. should not trigger a feed but a few time a season...ya got to know how much water is being added. Sometimes it took people 2 boiler replacements before they would finally listen...treat the beast nicely and it will treat u nicely