Condensate Question

[DAN Q]

NG Weil McLain GV4 Non-Condensing cast iron boiler has condensate drain which never drains. I cleaned the drain hole but still no condensate. The flue however seems to drain small amounts of condensate from a seem in a elbow about 2' feet from the boiler. Does anyone know if this is simply flue condensate, or actual heat exchanger condensate?

 

[Jadnashua]

A couple of points...depending on how it is setup, and used, modern condensing boilers may never actually condense the exhaust gasses. Second, the exhaust flue needs to be sloped back to the boiler, as described and pictured in the installation manual. Third, the condensate will be somewhat acidic, so depending on where it is actually discharged, it may benefit from neutralization. To condense, the supply and return water in the boiler needs to be much lower in temperature than in a conventional install. If it was not setup this way, it will not condense, and thus, won't be as efficient as it could be (assuming the load doesn't require it to be that hot). A CI boiler generally needs to run hotter, as condensing mode will cause excessive wear and erosion in the heat exchanger. It may condense momentarily or on a short fire, but should not be doing it regularly or it won't last long. Normally, the flue gasses will be hot enough so that they won't condense except maybe just when it first starts out.

 

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[DAN Q]

Thank you Jim, This is a NG cast iron boiler. The flue does slope back towards the boiler. I don't understand why condensate would drip from the flue joint seam instead of the drain tube. I think it may be possible the condensation dripping from the flue may be flue condensate condensing outside the boiler. It's a single wall flue, gases at two feet from the boiler might be cool enough to condensate. That would be good. I would feel better if I could rule out heat exchanger condensation, do you know a way to prove it out?t