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Main air vents whistling and spitting water on two-pipe system

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Ziamba
Ziamba Member Posts: 7
edited October 2020 in Strictly Steam
I tried searching the site for a similar issue, but could not find one, so I am sorry if this has been answered before.

I have an old steam heating system which appears to be two-pipe (each radiator has two pipes, one with a control valve, and the other with some cylindrical of attachment). We just got the system up for the first time of the season this past week. After it had been firing for that first time for about 45 minutes, I heard a loud whistling/venting sound coming from the basement. I went to investigate and found water spitting/dripping from a pair of vents on the main line farthest from the boiler itself. I then went to the boiler room where a second pair of vents close to the boiler were doing the same.

I checked the pressure gauge attached to the boiler, and it was about 4.5 psi. After several minutes of this, the boiler shut off and very quickly (within a minute) the whistling and spitting slowed and stopped as the pressure lowered.

I tried lowering the pressuretrol main setting, assuming it had something to do with the system pressure. It had been set to 9 oz/in2 so I lowered it to 5 oz/in2. Now, when the boiler fires, pressure builds up to about 1.5 psi, at which point the same four valves (2 pairs) hiss and spit for a short while until the boiler cuts out. Pressure stays at about 1.5 psi until the boiler cuts out, then it returns to 0 as the vents continue to release air and water.

Both pairs of air vents are stamped "Homman Specialty No. 75" with maximum steam ratings of 15 lbs.

Any ideas on what may be causing this problem?

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 23,313
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    Interesting. Your system has two pressure control devices: the "Vaporstat", which is set to cut the boiler off at 5 ounces per square inch -- that's the picture which you have labelled "pressuretrol", and a standard pressuretrol -- the picture which you have labeled "cutin" -- which is set to cut the boiler back in at 0.5 pounds per square inch, and -- most likely -- set to cutout at 1.5 pounds per square inch.

    Clearly either the vapourstat isn't working -- which does happen, though not that often -- or it isn't in the circuit to the boiler -- which also happens, but again not that often -- or it can't "see" the boiler pressure -- which happens frequently. Check to see how the vapourstat is connected to the boiler. There is -- or should be -- a looped pipe, called a pigtail, from the bottom of the vapourstat and connecting to the boiler. Odds are pretty good that that pipe is blocked, since the behaviour of the system changed -- some -- when you changed the main setting on the vapourstat, which suggests that it is working and is connected in the circuit.

    So the first thing to do is to take the vapourstat off that pipe, and make sure that the pipe is clear through into the boiler. If it isn't, clear it out or replace it.

    Then check again -- but that 0 to 30 psi gauge is utterly useless, even though it is required by code. You need a 0 to 3 psi, or 0 to 5 psi gauge, which can be mounted using a T, a few nipples and a couple of elbows, on pigtail with the vapourstat. If you find that the vapourstat is out of calibration, which happens, you can try to recalibrate it -- there are threads on the Wall about that.

    The Hoffman 75 is a good vent, though a trifle small by modern standards, and is not likely to be the problem.

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • BobC
    BobC Member Posts: 5,478
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    The vaporstat should control the boiler with the pressuretrol acting as a safety, Two pipe systems usually operate at low pressures - ozs not pounds. The two controls should be wired in series so either one can shut the boiler down.

    Do you know how old the boiler is? There is a gauge glass on that boiler that lets you see the water level inside the boiler, what is the level in that gauge when the boiler is resting and relatively cool. When the vents are whistling what is the water level and is the water level inside that gauge glass bouncing up and down much?

    It's possible the boiler needs to be skimmed, if the boiler water has any oils in it the water can bounce up and down quite a bit and this can cause the system to act strangely.

    Take some photo's of the boiler and it's piping from further back so we can see the boiler and the piping around it. This will let us see how it's configured. Where are you located, we may be able to suggest the names of good steam professionals in your area.

    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
  • clammy
    clammy Member Posts: 3,111
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    Looking at your pictures it looks like some did a little piping repair . Looking at the piciture I can’t tell if there is a pigtail on your vaporstat if not it may be be shot . Has anyone performed maintenance on this system say flush the wet returns ,clean pig tails and low water probes if applies and or the float low water cut off . It would be wise . The recent repair that was done they should have put a tee in place of the elbow to flush out the boilers water side . You should get a handle of the vaporstat and pressure issue and then check your main vents , I would think those two Hoffmann’s are ready for retirement . If they are not vacuum vents then replace w Barnes and jones big mouths if they are replace w the same and possibly raise there elevation . If you still have issue contact a pro from this site and they will surely getting it functioning correctly , where you located ? Peace and good luck clammy
    R.A. Calmbacher L.L.C. HVAC
    NJ Master HVAC Lic.
    Mahwah, NJ
    Specializing in steam and hydronic heating
  • CantabHeat
    CantabHeat Member Posts: 33
    edited October 2020
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    What everyone has said already, plus would just check around to make sure the vents are all working well (and bigger ones never hurt on the mains). Even with the vaporstat not shutting the system off 4.5 lbs (assimuming that’s an accurate reading) is way higher than the system should get to on its own if it’s properly vented and balanced. Other things I’ve seen:

    1. Giving the boiler a good cleaning is a good idea too. As mentioned if it’s dirty or has oils on the surface, strange things happen.

    2. Checking that the boiler is producing steam at a rate that make sense relative to the size of the system. A lot of boilers are oversized (salesmen convinced someone a more expensive bigger boiler will heat the house faster. It won’t). Alternatively, the boiler might be the right size but the system is partially shut down if a floor or many rooms have rads turned off which has the net effect of making the boiler “too big” . That too can lead to rapid pressure buildup once the main vents close and there aren’t rad vents to keep the venting going. 
  • dopey27177
    dopey27177 Member Posts: 887
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    In the picture shown as valve leak did you try dumping water from there to see if the return piping is clogged.

    Possible that the piping at the Hartford loop is clogged or the entry way into the boiler is clogged.

    Do you have an automatic water feeder that leaks water into the boiler slowly? Check your gauge glass for the proper water level.

    Since you have a compound gauge on the boiler did you ever see it go into a vacuum?

    Jake
  • Ziamba
    Ziamba Member Posts: 7
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    Thanks, everyone for all of the comments. Here is some more info on my setup, and a picture to boot

    The boiler serves a 1917 residential 3-story colonial in NorthEast Ohio.

    First, to answer Bob C: I am not sure how long the boiler itself has been installed, but there is a sight glass where the water moves up and down about 2 inches while the boiler is firing. I shut it down overnight and this morning the water was completely filling the sight glass.

    Jake, as I think back it may have gone to a slight vacuum (<1 in Hg) after the boiler and the vents stopped their noise. I am able to dump water from that pipe.

    I took Jamie Hall's advice to try checking the clearance to the vaporstat. The vaporstat was on a pigtail, attached to a pipe that connects the gauge, pressuretrol, and vaporstat+pigtail This pipe is connected to the top side of the automatic water feeder in an upside down J (see picture). I tried removing the vaporstat this morning and as I was removing it, water began coming up from where the pigtail meets the shared pipe. Not a few cups, but probably a gallon. I'm no professional, but that definitely doesn't feel right. However, it does seem to suggest that clogging there is not the issue.

    Any suggestions on how to really check the pipe is clear to the boiler?

    I tried draining from what I assume is the drain for skimming using the pipe and valve that comes off of the pressure relief valve (picture). I only drained about a gallon to see what happens and it came out in waves of clear and rust-colored.

  • CantabHeat
    CantabHeat Member Posts: 33
    edited October 2020
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    Thanks for the updates. For one the water level in the system is likely way too high. Every boiler has its own sweet spot but rule of thumb is that the water level is around half way up the sight glass when the system is off, as that marker label indicates. Water level too high could mean you have no real head space in the boiler for steam to develop and are blasting water up into your mains. Might not be the only thing going on but certainly isn’t helping. Would drain water down to the level indicated.
  • Ziamba
    Ziamba Member Posts: 7
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    Another update: I drained the water down until the automatic water feeder began to refill. As I was draining (from the LWCO valve) the water was VERY dirty. It looked like hot chocolate. I decided to shut off the water feeder and drain from each point until the water ran clear. Now I turned the water back on to the feeder and it is a little above the marked "Ideal" line and I still hear a faint flow of water from the feeder. I will wait until this flow stops and report back on the water level.
  • Jamie Hall
    Jamie Hall Member Posts: 23,313
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    "a fain flow of water" Problem. The automatic water feeder is a solenoid valve, and should be either clearly on -- or clearly and silently off.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Ziamba
    Ziamba Member Posts: 7
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    I am not sure mine is a solenoid valve -- It is a Mcdonnel&Miller series 51-2. It appears to have a float which simultaneously controls a cartridge valve and the LWCO. Though please correct me if that is incorrect!

    I went through the process of draining the water level to below my water feeder and using the manufacturer instructions removed the strainer and cartridge. There was a noticeable buildup of debris both in the basket and around the cartridge which I tried to clean. The instructions said to make sure the "poppet" moves freely, but nothing seemed to move on the whole thing. Maybe this is my problem?

    I put the cleaned cartridge and strainer back and turned on the supply water. The boiler didn't fire when I expected and the water continued to flow a little, so I gave the float lever a little downward pressure using a screwdriver, which both closed the valve and sent electricity through to the boiler. I will order a new cartridge and strainer assembly tonight.

    As the boiler heats, the air vents are still letting out a steady but small amount of air/steam. Is this normal?
  • Jamie Hall
    Jamie Hall Member Posts: 23,313
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    Oh. That's the mechanical valve one. From your description, either the float mechanism or the valve is sticking -- or both. How old is it?

    I might add that it has no provision for delaying the feed to compensate for a slow return -- to my mind, a fault.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Ziamba
    Ziamba Member Posts: 7
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    I am unsure, but would not be surprised if it is pushing 15-20 years.
  • Jamie Hall
    Jamie Hall Member Posts: 23,313
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    Might be time for a new one... maybe one which does have the delay, either probe type or the MM 67, either one with a VXT feeder with meter and delay...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Ziamba