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boiler fire and re-firing

Last week I skimmed a Dunkirk boiler for the first time in 23 years. I skimmed it over a 4 hour period but being that it was the heater's first time, I am well aware that the process will likely need repeating. NeXT I dropped two Steamaster tablets into the boiler, however the water in the sight glass is dirtier than ever before, which I assume is a good sign, but now the boIler keeps firing and re-firing in rapid succession. I still have a good amount of hammering near the boiler almost as soon as the cycle begins to heat the water and some hammering further away as well. I have a radiator on the first floor with a missing valve handle. I can't turn it on or off. I don't even know if it's open or closed. That's where a lot of hammering is happening. So my questions are as follows: how long before I drain the dirty water from the boiler and what could be causing the rapid re-firing all throughout the cycle? Is the pressurtrol to blame for the rapid recycling? Is the low water cut off malfunctioning? Thanks in advance for your help.


  • Jamie Hall
    Jamie Hall Member Posts: 20,857
    Did you start at the beginning? Is the pigtail for the pressuretrol clean and clear? Is the pressuretrol itself clean? Then... what is the pressuretrol set at? A "normal" one pipe or two pipe steam system runs at a maximum pressure of 1.5 psi; anything over that is likely to cause problems.

    Then. Does the water level bounce much when the boiler is firing? Did it bounce much before you skimmed it and put the SteamMaster in?

    (In fact, one might ask -- did you have the hammering, rapid recycling, etc. before the skimming and water treatment?)
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • KC_Jones
    KC_Jones Member Posts: 5,398
    How big is the boiler? 2 tablets may have been too much. On my boiler 2 tablets make it surge so bad that the boiler cuts out on low water after a while. It would do as you say cut out then the water settles out a minute later and boom fires again and repeats. This is another possibility. Watch the water level while firing and see if after a period of time if it is dropping rapidly and excessively, if it is the surging is a likely issue. The solution is remove some water and add fresh to dilute the water treatment.
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,573
    edited November 2015
    A stuck valve can often be loosened by turning the packing nut until it is almost off. Then the stem may turn.
    Don't forget to retighten, and check for seepage.--NBC
  • SWEI
    SWEI Member Posts: 7,356
  • heatseeker1
    heatseeker1 Member Posts: 72
    Jamie, my pressuretrol was replaced about 4 weeks ago and the pigtail was cleaned out. As far as I can tell, the pressuretrol appears to be set at 0.5 and the differential at 1. The water bounces less since the skimming and Steamaster but yes it does still bounce then eventually leaves the sight glass by dropping to the bottom. I have a two-pipe system. It is a 150,000 BTU boiler and I have 8 convection radiators and one vertical radiator. I did have the annoying hammering before the skimming and the rapid recycling seemed to have gotten much worse after I changed the thermoststat last Saturday. The old thermostat was not keeping the boiler on for more than 120 seconds per cycle. The heat anticipator mechanism wasn't doing a darn thing to increase the length of time that the boiler would stay lit, and something was wrong with the mercury bubble inside the old thermostat. I replaced it with a basic Honeywell round style thermostat and made sure to set the two little switches to the "on" position Before connecting the red and white wires. I must confess that I don't think that there is one properly working vent anywhere along the supply line.
  • Jamie Hall
    Jamie Hall Member Posts: 20,857
    Wait. Hold on. Slow down.

    If the water in the boiler is dropping that much -- out of sight -- your LWCO is going to cut off the boiler, or at least I certainly hope it will, and no amount of water treatment or other cleaning is going to help.

    You need to find out which control -- and it's not the thermostat, unless you have a wiring problem -- is causing the boiler to cycle. That's step one.

    Step two will be to find out why that control is tripping.

    A big drop in water level when the boiler finally makes steam may be a piping problem. Some photos of the near boiler piping might be rather helpful.

    I am rather surprised that the old thermostat had a problem. They are pretty well bullet proof, provided they are mounted level. The anticipator, if properly adjusted, will shorten the cycle enough to keep the building from overheating; that's what it's for. Even if it way out of adjustment, though, all that will happen is either the building temperature will overshoot or undershoot.

    But anyway, what's needed here is for you to find out which control is causing the cycling.

    Then we can begin to think about hammering (check all your pipe pitches to begin with, and the water level in the boiler vs. the height of all the wet returns).

    And later we can worry about skimming and all that.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Chris_L
    Chris_L Member Posts: 315
    Here's my homeowner's take on this, having used Steamaster tablets in a couple of boilers. If you put too many in, you'll get a lot of bouncing in the water line--and a lot of water can go out of the boiler, causing the symptoms you described.

    First thing I'd suggest is to drain half or more of the water out of the boiler while cold, fill it up, and fire again. See what happens with your water line.

    As for your radiator valve, you didn't say why you couldn't turn it. Is is just because the handle is missing? Take an adjustable wrench to the flats where the handle was and see if you can gently work it loose. (You should be able to compare the height of the valve stem to that of other radiators you have to tell if it is open (up) or closed (down.))
  • heatseeker1
    heatseeker1 Member Posts: 72
    Chris, the valve doesn't turn because it is frozen. It's unmoveable even after gripping the stem with a wrench. I did loosen the nut directly above the stem and both the stem and nut are fused. Evreytime the nut turns, the stem turns. I didn't retighten the nut yet because I want to see if that radiator heats all the way across and doesn't hammer. I placed a pot under the stem of the valve to catch any water.
  • heatseeker1
    heatseeker1 Member Posts: 72
    Jamie, I see that you recommend checking all the pipe pitches and the height of the wet returns. I would probably need someone other than myself to perform the first part. Of the pipes leading to and from the boiler there is at least 40 feet of piping running underneath a screened in panel in both the garage and along the basement wall. How does one begin to check the pitch of those pipes? Secondly are the wet returns the same notion as the long pipe through which the condensate travels back to the boiler or is it local to each radiator? (Please see picture of my style radiators).
  • heatseeker1
    heatseeker1 Member Posts: 72
    Dear Hatterasguy, Does using the 4" grinder apply to every valve line no matter what style radiator? Please send my pic. And when you say to flush the boiler 10x does that mean to empty it, fill it, then drain it x 10?
  • if the packing nut is stuck to the stem, then try unscrewing the bonnet of the valve, until the stuck valve stem completely unscrews. Then soak the whole assembly in liquid wrench. Put it in a vice, and break the bond between the packing nut and the stem.
    It's worth any effort to salvage the valve you have, so as not to need to remove the old spud, (a real chore!) when you replace the old valve with new.--NBC
  • Dave0176
    Dave0176 Member Posts: 1,176
    edited November 2015
    This is just my routine guys. I start by cleaning the pigtail, burners, gauge glass and LWCO. For extremely dirty boilers, especially those that have not been skimmed I'll skim it first. Then I'll dump that water add fresh, get it up to 10 psi if I can, blow it down, and add more fresh water, this time with 10-12 steam master tablets. I'll let it steam for about a half hour, at this point the water is usually black, then start dumping that water, adding fresh and steaming up and completely dumping the water over and over until it is crystal clear. Sometimes it also requires pulling the gauge glass off and possibly even the glass cocks because they get full of mud and keep dirtying up the gauge glass giving false impression the boiler is dirty. The final refill I'll add one to two steam master tabs. This routine works every time for me.
    DL Mechanical LLC Heating, Cooling and Plumbing 732-266-5386
    NJ Master HVACR Lic# 4630
    Specializing in Steam Heating, Serving the residents of New Jersey


    I cannot force people to spend money, I can only suggest how to spend it wisely.......
  • heatseeker1
    heatseeker1 Member Posts: 72
    Thank you Hatterasguy, Nicholas and Dave. I think I'll try removing the bonnet of the valve. What does the bonnet look like? Is that the next nut up from the packing nut?