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Old Cast Iron residential Boiler Help

JLJL Member Posts: 17
Can someone help me with servicing old cast boilers?  What is the procedure for cleaning and maintaining these boilers?  Here is the question/problem;  I recently got callled out on a no heat call and showed up to an old peerless cast boiler.  Fixed the no heat problem in one zone and then started looking around and noticed no one ever cleans these things.  So I took out the burners and cleaned them up, vacuumed out underneath the boiler.  Seems simple.  Put it all back together and now that the burners are burning a lot better when its running but,  I seem to be getting a little bit of a flame roll-out upon ignition.  Why would this happen?  If anyone has any input I would really appreciate it.  Thanks.


  • TimcoTimco Member Posts: 2,814

    You may have moved the orifices when the burner was out. Also, none of the adjustments you are seeking to make should be performed without a combustion analyzer. You may have even moved the pilot so it is not lighting the gas on the burner as quickly as it should. Sounds like a delayed ignition or too much gas being dumped in too fast. either way, a new symptom is not a good thing and needs to be corrected.

    Working on steam and hot-water systems isn't rocket's actually much harder.
  • JLJL Member Posts: 17

    Thanks for your input.  What is a combustion analyzer going to do for me?  I put a manometer on the manifold and it was reading about 2.5 inches of water column, which is acceptable.  I did adjust it a bit and it seems to be burning a lot better.  I checked the orifices and there size.  They are sized correctly.  Could it be possible that;  now that I don't have a lazy flame the heat exchanger could be dirty enough to give me a slight flame roll-out?  What is the worst flame roll-out you have seen?  Back then they did not have any sensors on them either.  The flue seemed to be drawing pretty good.
  • GordanGordan Member Posts: 891

    Is the rollout due to delayed ignition? As in, gas spills out but isn't lit until a few seconds later... at which point there's a "whoooomp"? If so, you may want to check that your pilot flame is nice and healthy-looking - if it's puny, try cleaning the pilot orifice. Also, the flame should be positioned properly.
  • John MillsJohn Mills Member Posts: 762

    seems pretty low on the manifold. Also did you clean the sections? Could be pretty dirty as well. 
  • JLJL Member Posts: 17

    I am going to replace the pilot  assembly and see if that helps.  Does anyone know what a combustion analyzer is going to tell me on a old cast iron peerless installed in 1972.  Is taking a flue reading a common practice on service calls when fixing a no-heat call.  Hasn't been the case for any company I've worked for.  My question is; At what point do you stop throwing money at these old boilers  and sell a new one.  I see a lot of old cast iron boilers that I think are safety hazards.  I tried to inspect the heat exchanger sections with a mirror and they are just as dirty as the burners where.  I guess I have learned my lesson on trying to clean these boilers up.  I just don't think it's worth taking apart the whole boiler and flue to access the sections and clean them.  Besides it would just make a huge mess and I just don't think I want to do it anyway.  Does anyone agree?  How do you tell people it just isn't worth the time and money?  Thanks for all the helpful input.
  • Combustion Analysis

    Hi JL:

    The combstion analysis tells you a lot; it's like a smog test on your car.  High carbon monoxide (CO) levels would indicate improper combustion, perhaps caused by a clogged heat exchanger that needs a good wire brushing between the sections.

    Would you like to be the mechanic that tells his customer that he needs a new car when all it needs is a tune up?

    Get a combustion analyzer and take a reading of the flue gases; then clean the sections and take another reading; odds are that the CO levels have come down.

    I had a customer once that had a Hydrotherm steam boiler; his mechanic told him that his boiler was a sectional boiler, that it had no flue passages to clean. As you know, it's just like your Peerless boiler and it has sections that need to be cleaned.

    All the best,

    Often wrong, never in doubt.
  • JLJL Member Posts: 17

    for the help Alan.  I have been on the new construction side all my life so I tend to lean to re-placement before fixing.  Something I will work.  In my defense some of these boilers and boiler rooms (with no combustion air) are just nasty.  Someone installed a closet install or crawl space install 35 years ago, shut the door and forgot about it.  Do you perform tune-ups on boilers and if so how do you go about inspecting the B-vent coming through the ceiling?  Are we supposed to climb up on the roof and pull the cap to get our eyes on as much as possible or even send a camera down it?  I have never done or heard of this but how can we guarantee it is a safe a reusable flue?  Is cleaning the heat exchanger, burners, and draft hood good enough for boiler tune-up?  Of course you still have maintenance to do on the hydronics side; Water, relief valve, air vents, ect.  Should re-placing the 35 year old gas valves be a standard with this kind of tune-up/maintenance?   
  • DennisDennis Member Posts: 79
    edited December 2009
    Flame roll out

    that you are experiencing is due to the boiler sections being clogged with soot.Yes gas can make soot, sometimes more than oil. This happens from clogged burners, causing a poor fuel to gas mixture. Now cleaning this is sometimes the problem, if the original installer ran the pipes back and forth over the top of the boiler. What you need to do is remove the flue pipe, the top of the boiler jacket, the collect box on top of the cast iron sections. Then put your soot vac under the boiler where the burners are, get the proper size boiler brush, push it between the pins or sections if it does not have pins. Either way clean off the cast iron surfaces to restore a path for the flue gases. Remove the burners and try to brush the surfaces just above the burners. Check the chimney for obstructions, make sure there is good draft. Now some boilers are accessed from the sides via little cast iron plates, use rust buster on the bolts and they should come off. Make sure that everything is furnace cemented shut again, no excess air through cracks. Put the whole works together and check the flue for excess CO, if you have it, the boiler is toast. Personally if the boiler is really old, and the HO has let it deteriorate I would replace it. New boilers have safeties that stop the boiler from killing everyone in the house. If the owner likes to run the boiler into a breakdown mode, this will be best.

    To be 100% sure about the boiler brush size, ask for a Weil Mclain brush and the next size up.
    Just do it, right.
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