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told 25 year old boilers better than new--really?

cowdoccowdoc Posts: 1Member
we use hot water baseboard radiators to heat the house. Main heat is wood boiler. Back up is 25 year old gas boiler. Had a pump go out and the repair guy turned out to be the one that installed the gas boiler. We asked him about installing a new gas boiler, say a 98% efficient one, as the current gas one can't keep up when it gets below 0 (we live in Wisconsin) and it definately is not the most efficient. Also the aquastat on the gas boiler only goes down to 190, the wood boiler pressure valve goes off at 190, so if we have the gas boiler turned on it runs constantly (not as true backup) as the water from the wood boiler looses some heat in 100 feet journey to house.

Repair guy said that we should keep the current gas boiler as if it gets some cold water on it it wont crack while the new ones will. To me cold water would only hit the boiler if a pipe bursts, so his logic seems odd.

Anyone here know if what he says's makes sense or have a good reason not to replace a 25 year old boiler?

Comments

  • EBEBRATT-EdEBEBRATT-Ed Posts: 5,617Member
    If your heating with baseboard the best you can do for efficiency is in the mid 80s, unless you want to add a ton of extra baseboard which is probably impractical.

    So your old boiler if it is in good shape and properl sized is probably as efficient as a new cast iron boiler. That's not to say that a 25 year old boiler may need replacement

    If you install a MOD CON boiler your efficiency will be in the mid 80s. You can't get to 90% or more unless you run low water temp which you can't do with your system.

    The mod con will get better efficiency if properly sized and do to a modulating flame
  • nicholas bonham-carternicholas bonham-carter Posts: 7,817Member
    All boilers, old and new can be damaged by cold water, so his reasoning does seem odd.
    The reason your old boiler will not keep up should be investigated, as it may not just be a case of it’s being too small. You could use the SlantFin app to determine your heatloss and compare that to the rating on the gas boiler. Maybe your radiators/baseboards are not big enough to supply all the heat produced by the boiler.
    Are you saying the aquastat will not regulate the water temperature below 190 degrees?—NBC
  • Solid_Fuel_ManSolid_Fuel_Man Posts: 1,454Member
    Could you post some pictures of your boilers? Also if you could follow the pipes and draw us a diagram of how the two boilers are piped and how the house is piped would be great.

    The cold water thing is very odd to say...
    Master electrician specialising in boiler and burner controls, multiple fuel systems, radiant system controls, building controls, and universal refrigeration tech.
  • HenryHenry Posts: 888Member
    Here in the Great White North, we replace boilers with mod/con on a regular basis. No baseboard system runs at 180F all season. Of the 1000 hours of burner operation only 100 hours during a very cold winter is run at 180F. Using the outdoor reset of the mod/con will save considerably your gas bill. BTW, I one looks the efficiency curves from many manufacturers, the efficiency at 180F is usually around 87%. So for 100 hours it will run at 87% the rest of the time it will be in the 90s.
  • SuperTechSuperTech Posts: 938Member
    I agree with @Solid_Fuel_Man that the fact that your boiler can't keep up on the coldest days is a huge problem and needs to be investigated before any other decision is made.

    Please post pictures of the boilers and piping, we can probably help save you a few headaches and a bit of fuel.

    I think from the sound of things that your wood boiler piping is the problem. That bit about it running constantly makes me raise an eyebrow. Most boilers I see are quite a bit oversized because no one likes to do heat loss calculations and bigger is better is the mindset of the day.
  • JacquesD23JacquesD23 Posts: 2Member
    I would be curious to see how your system is piped. Particularly how the "backup" boiler ties into the system. Also please list size of the gas boiler and pictures if possible.
    cowdoc said:

    we use hot water baseboard radiators to heat the house. Main heat is wood boiler. Back up is 25 year old gas boiler. Had a pump go out and the repair guy turned out to be the one that installed the gas boiler. We asked him about installing a new gas boiler, say a 98% efficient one, as the current gas one can't keep up when it gets below 0 (we live in Wisconsin) and it definately is not the most efficient. Also the aquastat on the gas boiler only goes down to 190, the wood boiler pressure valve goes off at 190, so if we have the gas boiler turned on it runs constantly (not as true backup) as the water from the wood boiler looses some heat in 100 feet journey to house.

    Repair guy said that we should keep the current gas boiler as if it gets some cold water on it it wont crack while the new ones will. To me cold water would only hit the boiler if a pipe bursts, so his logic seems odd.

    Anyone here know if what he says's makes sense or have a good reason not to replace a 25 year old boiler?

  • JohnNYJohnNY Posts: 2,220Member
    edited March 12
    Boilers today are better than boilers made 25 years ago.
    I think a case could possibly be made for boilers today vs boilers made 50 years ago though.
    For installations, troubleshooting, and private consulting services, find John "JohnNY" Cataneo here at :
    "72°F Mechanical, LLC"
    Or email John at [email protected]
    John is a professional Master Plumber, licensed by The Department of Buildings of The City of New York, and works extensively in NYC while consulting for clients in and out of state.
  • hot_rodhot_rod Posts: 11,252Member
    what I am seeing with new cat iron is they are much much less mass and water content, so short cycling will be more prevalent.

    But it sounds like you have either a load larger that what the boiler can keep up with, or not enough heat emitters.

    If the boiler burner is shutting down on those cold days, the problem is piping, heat emitter distribution related. If it runs nonstop, you may be out of horsepower :)
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • jumperjumper Posts: 1,300Member
    I see thirty year old laars and raypack still going. Will new ones hang in there so long? Is replacing a burner not easier than replacing a boiler?

  • John Mills_5John Mills_5 Posts: 895Member
    Since he uses his boiler as a back up to the wood boiler, it likely will be running pretty warm water so time spent with the boiler would be lots less than with the gas boiler as the sole heat source.
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