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Guess the schmoo

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gmcinnes
gmcinnes Member Posts: 118
Hi guys. My new boiler has been in operation for about a month now.

Because there were concerns about low return temps, and because I just can't leave well enough alone, I popped open the firebox and had a look. I discovered two piles of white powder. In both cases it appears at what looks like a seam in the firebox. It's sort of flaky, but also relatively well consolidated - i.e. it takes a good poke with a screwdriver to loosen a flake.

Any ideas what it is?






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  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
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    Looks like insulation off of the boiler door. In your first pic, if the entire door were a clock, look at the spot between 9 & 10.
    I'd vacuum it out, check again in a few months, compare pictures.

    There was an error rendering this rich post.

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,829
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    Low return temperature. What is your return temp? Refractory insulation stain looks like flue gas condensation combined with soot
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,505
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    Ed, do you think any refractory is missing where I mentioned (lower left side of upper left quadrant)? I'd suspect seeing more white crusties if it was condensing, not in just that one spot.

    There was an error rendering this rich post.

  • gmcinnes
    gmcinnes Member Posts: 118
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    @STEVEusaPA I don't think there's any refractory missing.
    Although the picture does give that impression, it doesn't look like it in person.

    @EBEBRATT-Ed It's a cold start boiler on a high mass system, with an outdoor reset. So, the return temps can be as low as 70F on the first gulp of a zone that's been off for a while. They usually get up to about 130F by 10 minutes. There's a long thread discussing the low return temps and the boiler bypass piping here.

    The TL;DR of that is that the delta T through the boiler is about 35F-40F and the flue gas temp is about 305F after about 10 minutes run time. Not stellar, but what do you think?