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Plumber says `Normal Corrosion` - Lochinvar Radiant Heat KBN080

I'm going through the process of purchasing a house and the radiant heat came up as an area of concern. I can't imagine that Lochnivar Radiant heat units have normal corrosion like this (attached image). The home owner had a HVAC specialist inspect said it was completely normal:

Boiler is in good working order the corrosion being reported by the home inspector is negligible. This corrosion is very common on Lochinvar boilers. The 4 tapping on the top of the stainless steel heat exchanger have had water seep from threads overtime. This happens due to the different expansion rates of the stainless steel taps versus the brass fittings. Several of the brass fittings have previously been replaced. None of these are active leaks and do no effect the performance or function of the boiler. There is rust in the bottom of the sheetmetal cabinet from a previously clogged drain that was corrected. The boiler currently operates properly and is not effected by any of the issues pointed out by the inspector.

I frankly find it hard to believe the the corrosion has no impact on performance but would welcome insight.
Model: KBN080
Serial: A07H1002447


  • whiskeydecisions
    whiskeydecisions Member Posts: 2
    Zman, thank you! Your insight is on point and appreciated.
  • Ironman
    Ironman Member Posts: 7,399
    Whenever there's a leak on a system, fresh water, with fresh minerals, is added to the system. Those minerals become bound to the heat exchanger and hinder heat transmission from the burner to the water. I totally agree with Zman about a complete cleaning and servicing on both th fire and WATER side of the boiler.

    Both Fernox and Rhomar offer chemical cleaners that will clean the inside of the system and de-scale the heat exchanger.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
    JUGHNE Member Posts: 11,108
    Also, just to point out to the OP that the system should always be under pressure of 12-15 PSI. If any of the suspicious areas were still leaking they would be wet.

    A simple test would be to shut off the city water supply and observe if the pressure drops on the gauge.
  • HomerJSmith
    HomerJSmith Member Posts: 2,511
    edited June 2020
    All corrosion is natural. It is a confluence of factors. The question is--is it desirable and what does it mean.

    Corrosion on a car battery, for instance, will leak current across the + and - poles and could inhibit current to the starter. That's undesirable if one is intent on keeping a charge and starting the engine.

    What I suspect from looking at your photos is that you have hard water in your system, which is greater concern to me as there can be calcification of the heat exchanger. 1mm of calcification on the walls of the heat exchanger will reduce heat transfer across the heat exchanger 12%. This can cause more serious problems with the HX with inability of heat moving from the gaseous flame to the water resulting in failures of the HX . If so, I would drain the sys and clean the sys and fix the leaks and fill the sys with good water.

    This is an older Lochinvar and may need the heat exchanger cleaned in the combustion chamber (different than my suggestion above) and a proper combustion analysis done with a recently calibrated meter. As suggested by Zman, above.
  • Robert O'Brien
    Robert O'Brien Member Posts: 3,548
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • HomerJSmith
    HomerJSmith Member Posts: 2,511
    Robert, I think the recall is for a Fire Tube boiler. Whiskeydecisions, has a Water Tube boiler. Thanks for the heads up.
  • Alan (California Radiant) Forbes
    Thanks for that recall information, Robert. Not a peep from my Lochinvar wholesaler.
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
    Robert O'BrienSuperTech