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bigger nozzle, still no pressure

Stewy_2 Member Posts: 83
Thanks, that make me feel better, The .85 80 nozzle is awesome but, now the smoke alarms go off and I get black smoke out of the flue. I know there is air vents I can adjust but how do I properly do that. I also have a Field Control RC type draft controller, should that need adjustment w/ the higher rate nozzle, the previous owner had it set at full open (I think thats where the smoke is coming from that is setting off the alarms) One more question. By the adjustable air vent on the burner there are numbers 0 - 10, what are they?


  • Stewy_2
    Stewy_2 Member Posts: 83
    NO Pressure

    My boiler WM P66HE runs and runs and only stops when the t-stat say to, it never builds pressure. I changed out the gauge and cleaned the pigtail. Manually I can trip the pressuretrol and it works. After no results from those projects I asked for some professional help. The guy that came to look at the boiler said it wasn't getting enough "juice" so he changed the filters (which were clogged as clogged could be)and bumped up the nozzle from an A .75 80 to a A .85 80. WOW did that thing make some steam, 25 minutes it took to get the house from 55 - 62, never seen that. The radiators heated almost all the way across, the air came out of the vents with force, but still NO pressure. Was the bump up in fuel just a band aide or maybe 25 minutes isn't long enough for a boiler to build pressure.
  • Ken Field
    Ken Field Member Posts: 127

    You said "The radiators heated almost all the way across, the air came out of the vents with force" The force was pressure. I don't know how much pressure you are looking for or where you are looking for it, but you obviously have pressure. If you are trying to read it on the gauge, forget it. They are a joke. I think there is another thread here about steam pressure gauges. If the system works better, it is fixed. Don't worry too much about the actual movement of a gauge needle.

  • ed wallace
    ed wallace Member Posts: 1,613
    no pressure

    dont worry about the bno pressure reading on the gauge you are geting pressure because the rads are heating
  • Mitch_4
    Mitch_4 Member Posts: 955
    sounds ok

    water when converted to steam expands about 1600x, that is the pressure to heat the rads, a steam system generally works on ounces of pressure so if you are looking for pounds, you wont see em.

    The system heated quickly and properly. maybe the gauge itself is no good
  • scrook_2
    scrook_2 Member Posts: 610
    how are the main vents?

    if they're undersized/missing/clogged then the radiator vents will have to pick up the slack, venting forcefully, as you say, and the radiators will be slower to heat than if the mains are vented well/quickly.

    Note you won't see the 0.25 to 1.5 psi (max) you'd like to have on a 30 psi (2x boiler/relief valve rating) gauge, but the mains and rad's will be hot. A 0-3, 0-5 psi, or thereabouts, in parallel to the 0-30 psi gauge on the pigtail would show some pressure though.
  • SpeyFitter
    SpeyFitter Member Posts: 422

    The kind of pressure that will be enough to show up on the gauge wouldn't show up until the vents on the mains and the vents on the radiators close. At that point you may get up to a pressure that will be readable on the gauge. If your radiators are heating all the way across, the vents on them should be closing. Are they?
    Class 'A' Gas Fitter - Certified Hydronic Systems Designer - Journeyman Plumber
    STEWY Member Posts: 1

    Shouldn't the Ptrol sense the pressure and shut off the burner. I have had the boiler run for 2 hours straight(its was running horribly prior to the cleaning and nozzle change and could not even statisfy the tstat) before and never indicate any pressure or tripped the pressuretrol . The mains are vented with Vent Rite #75 and all the rad have new vents. Also I just wanna be certian Im not overfiring my boiler and going to cause damage.

    PS I Love this site
  • Phil_17
    Phil_17 Member Posts: 178

    I'm just a HO steam fanatic so please listen to what the Pro's have to say on this, but one of the things that I've come to understand from running my own system, reading Dan's books, and lurking here on The Wall is that the matching of the boiler firing rate to the connected load is the key to proper operation of the system.

    As I understand it, a perfectly installed/operating system will never show any more pressure than the ounces it takes to distribute the steam in the first place.

    Think of it this way. At the peak load, the boiler is making just enough steam such that it can satisfy the rate at which all of the connected radiators and piping are capable of condensing it. The heat input at the boiler exactly matches the heat being radiated out in the system.

    If the boiler is over fired for the load, then yes you will make pressure once all the radiators are filled, and you should cycle on the vaporstat until the tstat is satisfied (they may tend to be sort of short cycles, but there is not much we can do about that).

    If the boiler is under fired, then you will never make any real pressure, but you will also have one or more radiators that never get hot all the way across.

    If you take an old house, update it with modern windows and add insulation to the attic and exterior walls then you will find that your radiators will never heat all the way across (unless you bump the tstat by a large amount), and your boiler will always run until the tstat is satisfied without ever making an appreciable amount of pressure.

    Once you think about it this way it is perfectly normal for the boiler to run constantly for a "long time" when you have changed the set point on the thermostat. This is part of the reason for the ongoing debate around here about whether it makes any sense to use a setback tstat on a steam system.


  • GW
    GW Member Posts: 4,676
    home made manometer

    spin off the gage and grab some cheap vinyl tubing at the hardware store, make youself a manometer and you will have actual inches of water column. 28" is one psi. re-install gage when you're done


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    Wilson Services, Inc
    Northampton, MA
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  • SpeyFitter
    SpeyFitter Member Posts: 422
    Gas Boiler Firing Rate Determination

    I love this site too.

    My boiler manual (Peerless 63-04L) gives the procedure for checking the firing rate. My boiler was installed by the previous homeowner (Yikes !!!) and so I don't know if he ever properly commisioned it after installation. I'm going to try to check it according to the following:

    6. Check the burner input by reading the gas meter.
    a. The required input rate is listed for each model in
    Section II, Dimensions & Ratings.
    b. Determine the input by multiplying “F” – Meter
    Reading (Cubic Feet of Gas) times “H” – Heating
    Value of Gas (Btu per Cubic Foot) times 3600.
    Divide by “T” – the time in seconds at the meter
    Rate, Btu/Hr = (F x H x 3600)/T

    For my boiler the required input rate should be 147,500 Btu/Hr

    The heating value of the gas can be obtained from the gas company, or as an approximation you can use: 1. Natural Gas Based on 1000 Btu./Cubic Foot, LP Gas Based on 2500 Btu./Cubic Foot.

    If you check this for yours, let us know what results you get. I would be interested in knowing.
    Class 'A' Gas Fitter - Certified Hydronic Systems Designer - Journeyman Plumber
  • scrook_2
    scrook_2 Member Posts: 610
    Bet he sees nothing

    'cause it's an oil burner, not NG! Oh well, seemed like a good idea.

    I assume that the W-M is a 3 section (P366HE), 13 3/8" deep not counting burner door or burner, rated 0.95 GPH (109,000 BTU/hr (453 sq ft) Net, and 340 Sq ft I=B=R, so 0.85 GPH is reasonable, and 0.95 is an option, though if it cycles off the Pressuretrol at the end of the cycle I'd go back to the 0.85 GPH.

    You don't want to be building excess pressure, 0.5-1 psi is plenty, a few ounces should do the job

    If, per chance it's a 466 (four section, 16 3/8" deep) it's rated 1.25 GPH, and should be fired at at least 1.0GPH!
  • ed wallace
    ed wallace Member Posts: 1,613
    no pressure

    Stewy please call your oil company you have a major problem there should never be smoke coming out of the smoke pipe from the draft control who ever worked on your heating system should have done an effiecy test after adjusting the fire
  • scrook_2
    scrook_2 Member Posts: 610

    I assumed the burner was set up using a combustion gas analyser or fyrite gauge, draft gauge, smoke tester, etc. when the nozzle was changed -- that would include (but not limited to): measuring CO2 (and/or O2) level in the exhaust, measuring stack temperature, overfire & breech draft pressures, adjusting the air shutter/air band, adjusting the draft damper, and conducting a smoke spot (Bacharach-Shell) test, etc.

    Set up right it should run like a champ. Low steam pressure is good by the way.
  • McKern_2
    McKern_2 Member Posts: 43
    boiler cycle/system pressure


    My question is a bit off the topic of this old thread, but you've touched on something that I've been wondering about for some time--i.e., if a "perfectly installed/operating system will never show any more pressure than the ounces it takes to distribute the steam in the first place," why do people fret when a system doesn't reach pressure?

    I can understand why a home owner might prefer to see the burner shut off a few times (not to the point of short-cycling, of course) before reaching the thermostat setting, rather than running constantly. On the surface, the first situation appears to burn less fuel. But this seems to contradict the part about "perfectly installed/operating system" (which, I'm assuming, would also be the most fuel efficient) building very little pressure.

    What is gained when the boiler cycles off due to pressuretrol/vaporstat? Is it a problem if the boiler typically runs without interruption until the thermostat is satisfied?

    Thank you for any help with this.

    (Needless to say, I'm a home owner, not a pro.)
  • Phil_17
    Phil_17 Member Posts: 178
    Perfect designs

    I think the people who fret about no pressure are homeowners who need some education... I know that was my first instinct when we bought our current home. I don't believe I've ever heard a pro fret about it.

    If the burner needs to cycle on pressure before the tstat is satisfied that implies to me that the boiler is oversized for the connected load. It may seem like you will consume less fuel this way, but the burner is actually burning more fuel PER HOUR in order to build that pressure, thus in the long run you will use less fuel if one is sized perfectly because the per/hour consumption is lower and the total run times will be very similar.

    In the real world, it is almost impossible to design a "perfect system". If you undershoot on the burner/boiler sizing then the radiators will not be able to heat all the way across, thus delivering less output than the system was designed to produce (perhaps not a problem if you have added insulation, modern windows, and otherwise tightened up the house), but you definitely run the risk of having cold customers on those "design days" when the wind is howling and the TV weather folks are ranting about how dangerously cold it is outside. Erring on the side of warmth, most boilers are sized with a little margin and thus it is not uncommon to have the boiler cycle a bit near the end of the run when all of the radiators are completely filled with steam and the vents have closed.

    This is the point where the value of a vaprostat is realized. If the burner is allowed to run it doesn't really have much impact on the amount of heat that is given off by any of the radiators (yes there is a small increase in temp as the pressure builds), so you really are just wasting fuel to compress the steam at higher and higher pressures. Cycling the boiler to keep the pressures low will minimize the fuel consumed while keeping the heat delivered at its maximum.

    Again, I'm not a pro. This is just my understanding based upon reading Dan's books, monkeying around with my own system (not the burner though), and a few years of college engineering to help fill in the gaps... If I've gotten any of this wrong I'm confident that wiser voices will educate me.

This discussion has been closed.