Flue Condensation


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Old 11-11-18, 10:47 PM
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Flue Condensation

So my NG non-condensing boiler has a drain for occasional condensate and I never see condensate drip from it. But I do see condensate drip from a flue seam about 3 feet away from the boiler close to the cold foundation wall. Is there a way to tell if this moisture is just condensing in the flue and not in the boiler itself? Or does mean if it's in the flue it's on the boiler heat exchanger as well?
 
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Old 11-14-18, 03:12 PM
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Usually flue condensation is caused by not enough heat going up the chimney. Some people try to save fuel by using a smaller nozzle to save a little cash, without researching it first. Just saying.
Sid
 
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Old 11-14-18, 08:42 PM
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Thanks Sidny, NG here, Everything is as it came from the Weil mclain folks. Flue condensate is OK by me. Heat exchanger isv my worry. I wonder if I could shove a scope up into the boiler through the flue to check the non flame side of the exchanger?
 
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Old 11-15-18, 10:25 AM
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You say that the boiler is non-condensing (i.e. atmospheric draft). What boiler water temperature are you running it at?

Usually a NG boiler should be run at minimum 130-140 degrees to avoid condensation. (Some that are specially designed can run lower--my Burnham ES can run at 100-110 and not condense.)

Is there any evidence of condensate drip below the heat exchanger? (On the gas tubes or the pan below them.)
 
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Old 11-15-18, 03:55 PM
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I would be leery of continuous condensation in the flue. Jack up your boiler water temp to 170-180. Let us know how that works.

Look at the exhaust plume above the chimney outlet. I like to see the plume clear just as it leaves the chimney.
 
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Old 11-20-18, 09:17 AM
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Water temp is at 180F. Plume is clear but I have seen it as a steamy cloud on very cold days last year.
Concentric venting through wall is used.I removed drain hose and place a container under the drain but it never collects any condensate.The flue is sloped back down toward the drain. If condensate did not leak out the flue seam I think it would flow to the drain hole. How much condensate is to much?
 
 

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