20 year old Knight KBN080

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Boring
Boring Posts: 56
in Radiant Heating

Thinking it's time for a new boiler…any recommendations for a great replacement? I've taken care of this one for it's entire life….Is replacing it something that a competent home owner can successfully accomplish?

Boring

Comments

  • pecmsg
    pecmsg Posts: 7,634

    No need to replace due to age. Any issues, short cycling, leaks, etc?

    Can a homeowner do yes.

    Boring
  • hot_rod
    hot_rod Posts: 28,699

    why? I think parts are still available. The only killer would be a leaking heat exchanger

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    IronmanHomerJSmith
  • Boring
    Boring Posts: 56

    Well, Last year when I cleaned the boiler the insides were looking pretty crusty as was the burner and the gasket on the burn chamber and the display has been flickering for a couple years now. Called a service company to service this year and they indicated that old girl is probably due to be replaced and they are so busy they couldn't do it, they gave me a couple recommendations and they are booked out several weeks to….so I decided to rip into it yesterday…replaced the backflow valve and pressure reducing valves cause the boiler had no water pressure….working great now, but haven't cleaned the burner or taken that apart yet…concerning that maybe it won't seal back up….worried crazy old man I guess…. considering a KHB085 as a replacement…thoughts, and Thank you!!

  • EdTheHeaterMan
    EdTheHeaterMan Posts: 12,940

    Basically the same input and operating design, modulating and condensing. Check the I/O manual to see if the existing venting is adequate and if it is not, is it easy to install the required vent piping?

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    Boring
  • hot_rod
    hot_rod Posts: 28,699

    well I suppose it is a matter of when , not if it will fail. I doubt price is going down.

    I like the Knights, I have installed quite a few since they came out. I have a 50k in my shop.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Boring
  • Boring
    Boring Posts: 56
    edited October 21

    thank you for your thoughts and guidance…venting is ok, co-vent out a side wall, appears the boiler that caught my eye has a little different configuration but should work, everything else is just pipe fittings/sweating and air elimination…. Maybe I'll clean her up one more time and keep my fingers crossed that nothing goes haywire, or see if I see any concern spots before I pull the trigger….. guess I'm "waffling" now….

    Peace to all…Boring

  • EBEBRATT-Ed
    EBEBRATT-Ed Posts: 21,328

    @Boring

    If you can keep this one running buy the new boiler now and have it ready. Reolace it in the spring when you can take your time and do it right.

    Study the piping, wiring and venting in the new manual and take the time to get everything right

    GGrossBoring
  • GGross
    GGross Posts: 2,104

    Looks like you have a floor mount, so to keep it simple maybe the Lochinvar KHB085? biggest difference will be new control and its a fire tube now instead of water tube. NTI has the NC085 which would be similar, but check the built in close spaced tee which you may need to valve off. if switching to a wall mount you have options of similar or the same size from pretty much all of the big manufacturers.

    Boring
  • Boring
    Boring Posts: 56

    I have an indirect water tank also…looks like the NIT NC085 doesn't work with an indirect…but thank you!!

  • 109A_5
    109A_5 Posts: 4,759
    https://forum.heatinghelp.com/discussion/comment/1907319#Comment_1907319

    Why not ?

    image.png image.png
    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System
    GGross
  • GGross
    GGross Posts: 2,104
    https://forum.heatinghelp.com/discussion/comment/1907319#Comment_1907319

    They all work just fine with an indirect 🤣as a matter of fact you have multiple options to hook an indirect to the NC085, you can hook it direct to the boiler and use the internal circ, or pipe it with its own pump external to the boiler you may be thinking of the compass combi models that you would not want to use an indirect with

  • Boring
    Boring Posts: 56

    I just noticed too, the knight boilers are not condensing boilers anylonger…what changed? Seems like a pot of water sitting in the bottom of a boiler would be less efficient…?

  • hot_rod
    hot_rod Posts: 28,699
    https://forum.heatinghelp.com/discussion/comment/1907370#Comment_1907370

    `About the only change is they went to the fire tube HX about 10 years ago, the first Knight came out in 2005.

    Still a modulating, condensing boiler. One of the best.

    Screenshot 2026-10-23 at 9.47.54 AM.png
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • GGross
    GGross Posts: 2,104

    Every boiler is a condensing boiler if the return water is cool enough 😊

    But seriously like @hot_rod said. the Knight is a modulating condensing boiler.

    You maybe read something somewhere that a particular install didn't condense, which is true of all condensing boilers. return temperature gets high it can't condense, that's just physics

  • Boring
    Boring Posts: 56

    ….Well that is re-assuring, I love this site and the openness that experts have to express and share their knowledge… I was viewing comparisons of the burn chambers...my current knight has the burner going into the coils at the bottom of the boiler....this one I've been viewing appears to have the burner shooting down…what exactly does "fire tube" mean? I gathered that spent hot gasses were sent through the "fire tubes" to heat the boiler water.... Excuse my ignorance please and thank you again for helping me understand the differences.

    J

  • hot_rod
    hot_rod Posts: 28,699

    Earlier mod cons were based on the water coil boiler from Giannoni, now Sermeta, a French company.

    Many have moved to fire tube design. Larger commercial sizes are still often the water coil design.

    So with a coil type water tube the water is inside the coiled tube, burner inside the coils.

    Fire tube design the flame goes down thru the tubes, water surrounds them.

    Pros and cons to either. I preferred the coil type, easier to clean if the maintencenance gets away from you.

    Also less welds which is a common failure point.

    Proper cleaning, combustion adjustments and water quality and either type should last 20 years or more.

    Screenshot 2026-10-23 at 12.39.18 PM.png Screenshot 2026-10-23 at 12.37.12 PM.png
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Boring
    Boring Posts: 56
    edited October 29

    Thank you very much!!! I've spent the whole afternoon watching a tech servicing a couple knight fire tube boilers…It was educational…one of them was down because of a weld issue and the other had not been serviced in several years. I guess I feel comfortable with that design, and based on the name brand it should last as long as the one I currently have…. Have a nice weekend.

  • Boring
    Boring Posts: 56

    ……NEW update……

    Took her apart and cleaned her up and decided to order parts for the weak spots…The fiber disks and a burner chamber cover….was thinking about a burner also…but..the one in there appears OK…do they come out of the cover easily or will it get damaged during the cover switch…new ones are pricey and hard to find….Thoughts?

    Thanks a bunch for your thoughts…

    B

  • hot_rod
    hot_rod Posts: 28,699

    You can get various gasket kits, like this.

    Unless combustion is way off, the burner should not be breaking down.

    Screenshot 2026-10-30 at 9.54.40 AM.png
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream

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