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How long will my boiler last? Looking for your best educated guesses.

WarmJamesWarmJames Member Posts: 14
You know how when you start out painting the kitchen and you end up doing a full remodel? Like you know, mission creep. Well, that may be what I'm doing here with my radiant system, and I wanted to get some professional opinions on the subject.

So I have a thin slab radiant system I installed 27 years ago when we built the house, and it's been just fantastic, I will never have another kind of heat. The heat source is a Raypak 260 K BTU cast iron boiler that has been flawless (minus a spark module of course). So now what is happening is the vent hood is starting to rust out and no big deal, 200 bucks for a new one and it's done right? (this is where the mission creep part comes in) So I started thinking, I wonder how long this boiler is going to last?

let me back up a little bit, in my view this boiler is dramatically oversized, I run it at its lowest possible temperature which is 105°F and typically the gas valve modulator is running at what must be it's lowest position, very little flame.
I live in California which is a pretty moderate climate, rarely getting to freezing at night. So I'm thinking I could probably get away with about ~100 K BTU boiler and it would be just fine. Obviously take longer from a cold start, but that's not very often. Even then the boiler runs on high for only a couple minutes, because the boiler generates way more heat than the slabs can absorb.

in addition these wall-mounted condensing units are about the quarter of the size of the 260K monster that takes up a good portion of my utility room, so I could also gain some space in the process.

looking at the existing boilers burner compartment, it looks relatively clean, with no signs of any scaling dropping down from the heat exchange tubes and the burners themselves looking good. (I don't see where I can post a picture on this forum or I would)

So my question is, from all your experiences, what kind of service life should I expect from the existing boiler and any other thoughts on going with a smaller condensing unit? And, what brand of wall-mounted units does everybody like?
Thanks for taking the time to read this long post and for any wisdom you may have for me.


  • SuperTechSuperTech Member Posts: 1,390
    The cast iron boilers last a lot longer than condensing boilers, with less service requirements. That boiler could outlast you, potentially.
    Sizing a boiler is not guesswork. You have to do an accurate heat loss analysis on the home. Download the Slant Fin app if you want to get an idea of the boiler size you need.
  • Jamie HallJamie Hall Member Posts: 13,207
    Fix the vent hood and be happy. As @SuperTech said, that boiler may well outlast you.
    Br. Jamie, osb

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • hot_rodhot_rod Member Posts: 13,737
    Has to be a copper tube boiler, I don’t think Raypak made cast?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
    delta TCanuckerkcoppSteve Minnich
  • WarmJamesWarmJames Member Posts: 14
    I meant the end caps were cast-iron, not bronze.
  • EBEBRATT-EdEBEBRATT-Ed Member Posts: 7,227

    Are you running this boiler at 100 degrees or do you have a mixing valve on the water? With you moderate climate and a 260,000 btu boiler how big is the space your heating??

    I don't think Ray-Pak makes an all CI boiler as @hot_rod mentioned
  • kcoppkcopp Member Posts: 3,523
    It is a Laars design boiler. Similar to the Teledyne -Laars Mini-therm units. IF it is properly cleaned and taken care it could go another 10 years.
  • WarmJamesWarmJames Member Posts: 14
    I believe that the heating tubes themselves are some nonferrous material, but end caps are cast-iron.

    Ed, now that I think about it I believe the main loop going through the boiler is at 110°F (set with the thermostat inside the boiler), and the 3 individual Main house area mixing valves are set for 105°. There are 16 individual zones/rooms connected to those 105° loops. The house is about 6000 ft.², but typically only heating about six zones/rooms at any given time. (The beauty of radiant is that if you heat the downstairs, the bedrooms upstairs stay at just the right temperature without sending any water there)
    kcopp, how do you recommend I properly clean the boiler?
  • EBEBRATT-EdEBEBRATT-Ed Member Posts: 7,227
    Basically you take off the flue and flue box, pull out the burner tray and all the burners. Then you can get at the hx and brush/clean/hose it off.

    Most soot and debris will be on top of the HX

    Stick a light in where the burners goes and when you look down from the top you will be looking through the hx at the light.
  • icy78icy78 Member Posts: 372
    90f EWT .
    A condensing copperfin?🙂
  • WarmJamesWarmJames Member Posts: 14
    Thanks Ed,
    I can do that when swapping the vent hood.
  • ZmanZman Member Posts: 5,948
    The vent hood has rusted out because you are running a non-condensing boiler at condensing temps. I suspect that your B vent has rusted out as well. You should inspect the vent, especially near the top to check for damage.
    If you continue to run your boiler, it should be repiped to avoid condensation.

    In a case like yours, you should save >30% in gas by going with a properly sized mod/con.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • ZmanZman Member Posts: 5,948
    To answer the how long will it last question, how long has the temp been set that low?
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • WarmJamesWarmJames Member Posts: 14
    Set at 110F for 27 years.
    B vent looks good just looking from what I can see from under vent hood inlet.
    What temp do you reccomend?
  • icy78icy78 Member Posts: 372
    > @WarmJames said:
    > Set at 110F for 27 years.
    > B vent looks good just looking from what I can see from under vent hood inlet.
    > What temp do you reccomend?

    Almost makes one think it's been spilling fluegas out the drafthood the whole time.
  • WarmJamesWarmJames Member Posts: 14
    "Almost makes one think it's been spilling fluegas out the drafthood the whole time. "

    What makes you say that?

  • CanuckerCanucker Member Posts: 620
    If the B vent is in good shape and you had to replace the draft hood, it means it was spilling damp exhaust until it got hot enough to rise to the top of your chimney, hence the rusted draft hood
    You can have it good, fast or cheap. Pick two
  • EBEBRATT-EdEBEBRATT-Ed Member Posts: 7,227
    You should run the boiler so that the mixed return stays above 130 going into the boiler. Use a mixing valve to supply the radiant. Supply temp from the boiler needs to be high enough so the return stays above 130. Trial and error Probably 140-150

  • WarmJamesWarmJames Member Posts: 14
    OK thanks for the insight on this guys, I did some reading and now understand the problem with the low temp. This is my fault for going on the premise that running the whole system on lower temperature is easier on all components. I have now adjusted return temp to 130° F. Here is what hood looks like:

    sent a camera up the flue and it looks good, dodged a bullet i think.

  • EBEBRATT-EdEBEBRATT-Ed Member Posts: 7,227

    You have to use a mixing valve too much heat will be bad for the radiant system which should run at 120 supply max
  • WarmJamesWarmJames Member Posts: 14
    I do and they are set at 105
  • EBEBRATT-EdEBEBRATT-Ed Member Posts: 7,227

    K. You should be all set then.
  • JUGHNEJUGHNE Member Posts: 7,103
    I see there is a plugged vent safety limit in the hood.
    Has it ever opened that you are aware of. It may be auto reset so it could have gone unnoticed.
  • WarmJamesWarmJames Member Posts: 14
    JUGHNE said:

    I see there is a plugged vent safety limit in the hood.
    Has it ever opened that you are aware of. It may be auto reset so it could have gone unnoticed.

    Not that I am aware of, why do you ask?
  • JUGHNEJUGHNE Member Posts: 7,103
    If your flue was not drafting up thru the chimney/roof cap and the vent hood was "spilling" exhaust gases out that safety limit should open and shut down the fire.
    It might auto reset after cool down and refire.
    If auto you may not have noticed.
    Manual reset limits have a small red button outside between the wires. Do you have the reset button on yours?
  • WarmJamesWarmJames Member Posts: 14
    Yes on button.
  • icy78icy78 Member Posts: 372
    Thing is....there's no directions or arrow, showing the flue gas that if it wants to must exit past the spill switch.
    I've seen lots of spillage that did not affect the spill switch.
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