Direct vent VS concentric


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Old 10-31-18, 11:19 AM
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Direct vent VS concentric

When the weather is cold is there an advantage with using indoor air as opposed to outdoor air for venting natural gas boilers? It would seem that warmer indoor air would be more efficient, easier to heat than cold outside air? Also would colder air cause more condensate across the heat exchanger and flue?

t
 
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Old 10-31-18, 03:36 PM
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I think there may be a misstatement here. A boiler's "venting" is the exhaust. I think you mean the boiler's combustion air supply. But, anyway, using indoor air would be a bit more efficient, boiler-wise.
 
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Old 10-31-18, 03:57 PM
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It may be a little more energy efficient using indoor heated air.... but.... you paid to heat that air.
So I'd lean towards bringing in fresh air for combustion.
 
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Old 10-31-18, 07:11 PM
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I do mean combustion air supply. Will cold winter air supply cause more condensate in non- condensing NG boilers?
 
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Old 11-03-18, 07:51 PM
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Zone7: Will cold winter air supply cause more condensate in non- condensing NG boilers?
The colder outside air is the lower its due point. Boiler firing chamber due point/ condensation typically occurs at 133F.

The relationship between the two is not significant. Theoretically there might be less condensation.

The boiler setup with adequate margin would preclude condensation so it should not be an issue.
 
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Old 11-04-18, 06:35 PM
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Thanks. All good information.
 
 

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